Alert, Alert, Alert----- Transmission valve body wire housing block! --- Have you looked into yours? Capillary action drawing ATF in!

[2001LC]

This automatics transmission's (A/T), wire housing block on driver side (LH) of A/T. Which connects to solenoids & temp sensor(s) within A/T case on valve body. Is heavily coated inside with a gray/green GOO. What is this GOO?

Any guesses what thick appearing oil substance is?

Anyone have pictures or can comment on theirs, they care to share here?

Edited 12/14/25:

As you read through this thread. It will become apparent we've ATF capillary actuation issues with: Transmission wire, that come out of A/T case from inside transmission. It's the wire housing, that connects all valve body solenoids.

Checking and replacing this wire harness and sending a sample of ATF, out to Blackstone. Is something we may need to start doing as a PM. If analysis report of ATF sample, show higher than normal insoluble. 12 qt ATF flush, ASAP. Even adding inline filter temporarily. Rested ATF few thousand miles later or if any shift issue.. May be a good course of action, we all need to do.

Nobody, needs to runout and buy these wire harnesses! Even if, they find grease in wire housing block.
At this point. This is a Exploratory Fact Finding Alert. Which I edited heading, to alert (perhaps unjustly).

Inside wire housing block, that sits on side of transmission. Anyone seeing oil in theirs?

Looking on driver side (LH) of transmission.

Wire hosing block. Unlocked, by just pulling outward from top center of white plastic lock. Then pull down the whole lock arm.

As the whole lock arm is pulled all the way 90 degrees down. It unlocks and lifts the male off, the female wire housing block its attached to. Then pull up the male wire housing with its locking arm, to separate. Trick is to have lock arm swung, all the way down 90 degrees.

Anyone seeing oil in their A/T wire housings blocks?
Male wire housing. Which is part of main wire harness, that straddles over outside of entire A/T like an octopus.

Female side, wire housing block. Which 10mm bolts hole onto A/T case. Where it penetrates into case attaching to all solenoids and has ATF temp sensor attached end or wires.

Goo is likely just old used ATF & dielectric grease mix. That mixed and aged, in wire housing block. Which would indicate a longer term issue, undetected (no apparent issues) for years. With time (heating and cooling cycles. Would it have affect on current flow? Effects like increased resistance and or cross current between pins.

 

[2001LC]

Is it possibly, ATF or some sort dielectric grease (DG) or mix looks like this GOO. If just ATF color seems wrong and looks to thick. If just DG, should be thicker at 60F. So mix perhaps

First two pictures below. Are from a 07LX w/170K, presumed P/N 82125-35150 vs new P/N 82125-60651 Transmission wire (CASE to valve body) harness.

Old 07LX W/170K miles presumed P/N 82125-35150 Transmission wire (CASE to valve body) harness

Newest P/N 82125-60651 Transmission wire (CASE to valve body) harness.

The gloss seen in bottom. Is a hard solid substances. It appears some injection tool fits over pins, sitting with end square at bottom. You can see a square at bottom is not coated (glossy). Did new wire harness adequately address capillary action. IDK! So we'll need to keep inspection on PM list.


Below is one of wire housing block. On Main Transmission wire harness (octopus) that straddles A/T. The one with locking housing block male end, that connect to CASE harness.
Factory installed on 07LX A/T. Presumed P/N 82125-60580 (no change in 06-07 P/N seen at this time).

If we don't get ahead of this. We could end up with, very costly repair bills.

We've not seen many 100 series, with automatic transmission (A/T) issue. But same A/T A750 is in many makes and model, which are seeing issues: Shifting, A/T valve body and O2 issues. We may find the root cause. Began with electric short in wire housing. So as 100 series fleet ages. We'll likely see the same!

Where I'm I going with this thread:

1. Alert and Recommend a PM.

We need to:

• Identify original P/N, that can in vehicle and it's issue.
• Identify any replacement harness "P/N" that fix or subsequent had issue.
• Which years, makes and models.
• Use info to know what to look for in which years with which wire harness. i.e. Goo, ATF, oxidation or corrosion in wires and or wire housing block(s).
• Identify further down and upstream issues and damage. Caused by defect wire harness.
• Identify and correct design defect, of wire harness(s).

To help guide us. We need info from outside the 100 series community, also. Seems other makes and models with A750 & 760, are seeing issues before us.

 

[Malleus]

That looks like water & engine oil to me.

 

[Unrulykid]

Is it possibly, ATF or some sort dielectric grease (DG) or mix. If just ATF color seems wrong and looks to thick. If just DG, should be thicker at 60F. So mix perhaps

I've seen, in some wire housing blocks. Like on remain alternators. They'll come with an off white grease within the wire connector block. Could that I have mixed of some D-G, with ATF that wicked up through wires. Resulting in this color and consistency

I did spray undercarriage with PB Blaster long lasting undershield. Which is this color and consistence. But I can not, see any, on wires or even in area of wires or wire housing blocks.

Anyone seen, a color and consistence like this oily looking substance?
View attachment 4036501

I cannot be sure from the photos… but it appears that whatever that viscous fluid is, it is contained within the weather seals of the electrical connector.

That tells me that it was put there on purpose ( but that would take very careful application so as to not get it onto the interior surfaces of the electrical connector housing), or, it came out of the transmission ( more likely), and it did not come from outside the electrical connector.

What does that stuff smell like?

Not fun, but you could de-pin a few of the pigtail end wires to see if the offending stuff is wicking up the wire harness.
ATF wicks. Dielectric grease does not.

What issues prompted you to look into this connector?

 

[TwistedCon]

Mine never looked like that but I did just post this thread the other day. 2004 Transmission Solenoid Issues - https://forum.ih8mud.com/threads/2004-transmission-solenoid-issues.1371996/

Curious what others look like because I just picked up my new harness today and plan on installing it soon.

 

[2001LC]

Mine never looked like that but I did just post this thread the other day. 2004 Transmission Solenoid Issues - https://forum.ih8mud.com/threads/2004-transmission-solenoid-issues.1371996/

Curious what others look like because I just picked up my new harness today and plan on installing it soon.

I did see your thread, and saw blue oxidation/corrosion in a few of the wire housing block pin holes. For sure, that will cause essive resistance.

We've other threads, one guys replace TCM and more. In the end, it was wire harness R&R that corrected issue.

Here's a video, showing a 100 series dissemble. The only thing found to be issue. Was corrosion in same wire housing block as yours and shown here with oily substance. It was unclear what issue, prompted this tear down. Apparently, A/T was brought to them for rebuild.


I've found a ton, of info on the A750f and e and 760 valve bodies. Where valve body has issues. The issues, are mainly centered around wear in port and on valves. But seems we're not see this in our 100 series. Feeling is ours A/T fluid runs cooler. Fluid is key to, reduced wear.

 

[Malleus]

That blue oxidation is coolant induced. It happens frequently to the 80s, because the heater bypass hose (AKA PHH) leaks onto the engine–transmission harness connections. Sometimes I think Toyota put them there to keep the coolant off the starter.

 

[TwistedCon]

That blue oxidation is coolant induced. It happens frequently to the 80s, because the heater bypass hose (AKA PHH) leaks onto the engine–transmission harness connections. Sometimes I think Toyota put them there to keep the coolant off the starter.

Its crazy you mention that. About 11 months ago my heater-t gave out me, got it fixed pretty quickly but got coolant everywhere when it blew out.

A month later on a road trip transmissions issues came up which turned into insane repairs bills, no car for over 6 months, credit card charge backs and everything. The first thing I told that shop though was the coolant going everywhere and that it could of been the issue.

Curious though I don't believe I am losing any coolant anymore but now you made me curious and i'll be double checking the connections.

 

[EAST TN 07LX470]

Is it possibly, ATF or some sort dielectric grease (DG) or mix. If just ATF color seems wrong and looks to thick. If just DG, should be thicker at 60F. So mix perhaps

I've seen, in some wire housing blocks. Like on remain alternators. They'll come with an off white grease within the wire connector block. Could that I have mixed of some D-G, with ATF that wicked up through wires. Resulting in this color and consistency

I did spray undercarriage with PB Blaster long lasting undershield. Which is this color and consistence. But I can not, see any, on wires or even in area of wires or wire housing blocks.

Anyone seen, a color and consistence like this oily looking substance?
View attachment 4036501

This is exactly what mine looked like when I was having issues a recently. See my thread below.

E

Thread '2007 Lexus LX470 P0776 & P2714 Transmission Shift Issues'

Aug 29, 2025

Looking for suggestions on where to start with troubleshooting. I have a 2007 Lexus LX470 with ~282,000 miles. Just today when merging onto the highway at ~75% throttle the transmission failed to shift from 3rd to 4th gear. The entire way home it would shift 1-3 and slip randomly in the lower gears. Got home and pulled P0776 and P2714 from the ECT in techstream. Codes are for pressure control solenoid B & D performance or stuck off. Tried clearing codes and disconnecting the battery for ~15 minutes. Same issue after driving again. I am getting ready to check AT fluid level. I did change...

• EAST TN 07LX470
• Replies: 15
• Forum: 100-Series Cruisers

 

[2001LC]

That blue oxidation is coolant induced. It happens frequently to the 80s, because the heater bypass hose (AKA PHH) leaks onto the engine–transmission harness connections. Sometimes I think Toyota put them there to keep the coolant off the starter.

In case of blue oxidation in A/T wire housing block, I was alluding to. It's very unlikely related to coolant in these cases. The housing block, is the one near back of A/T of lower diver side. I've near seen coolant on this block. They housing block, has water tight seals inside and pig tails have rubber seal. The seals do fail.

Add moisture to copper, we get blue green oxidation. I've found more than one system with oxidation, that increased resistance of a wire. Due to oxidation on contact pins within a wire housing block or even pins of a fuse.

I had not, though much about ATF on contact pin, have same effect. But apparently it does, with time.

Here's the one I referred to: red is seal, blue arrows point to pins with blue oxidation. No sign of any oil. But he to had A/T shifting issues.
Taken form @TwistedCon thread 2004 Transmission Solenoid Issue

Once in the "Big 3" thread. I posted about a conversation I had with airframe mechanic. He said, :when you see this oxidation in wire, you can bet it has travel under sheathing along wire strains. Which result in increased resistance. When they see oxidation on wires. They don't bother testing resistance. They just replace.

Examples, below are to show various colors and looks. Of other than oil, causes of electrical issue.
I see: Some blue, some white, some just dirty looking oxidation some rusty corrosion. These are for the most part moisture, acid and or salt related. None were near coolant. All have increased resistance. All result in electrical issue.

This is exactly what mine looked like when I was having issues a recently. See my thread below.

E

Thread '2007 Lexus LX470 P0776 & P2714 Transmission Shift Issues'

Aug 29, 2025

Looking for suggestions on where to start with troubleshooting. I have a 2007 Lexus LX470 with ~282,000 miles. Just today when merging onto the highway at ~75% throttle the transmission failed to shift from 3rd to 4th gear. The entire way home it would shift 1-3 and slip randomly in the lower gears. Got home and pulled P0776 and P2714 from the ECT in techstream. Codes are for pressure control solenoid B & D performance or stuck off. Tried clearing codes and disconnecting the battery for ~15 minutes. Same issue after driving again. I am getting ready to check AT fluid level. I did change...

• EAST TN 07LX470
• Replies: 15
• Forum: 100-Series Cruisers

Did you get any pictures, that you care to post here?

 

[white_lx]

Mine was soaked in ATF. I discovered it because it was destroying A/F sensors. It was a wild ride. Here is the complete story: Oil wicking into ECM - random A/F sensor codes P0171/P0174/P2195/P2197 - https://forum.ih8mud.com/threads/oil-wicking-into-ecm-random-a-f-sensor-codes-p0171-p0174-p2195-p2197.1322776/

Here is a picture of that thread.

 

[EAST TN 07LX470]

In case of blue oxidation in A/T wire housing block, I was alluding to. It's very unlikely related to coolant in these cases. The housing block, is the one near back of A/T of lower diver side. I've near seen coolant on this block. They housing block, has water tight seals inside and pig tails have rubber seal. The seals do fail.

Add moisture to copper, we get blue green oxidation. I've found more than one system with oxidation, that increased resistance of a wire. Due to oxidation on contact pins within a wire housing block or even pins of a fuse.

I had not, though much about ATF on contact pin, have same effect. But apparently it does, with time.

Here's the one I referred to: red is seal, blue arrows point to pins with blue oxidation. No sign of any oil. But he to had A/T shifting issues.
View attachment 4036992
Once in the "Big 3" thread. I posted about a conversation I had with airframe mechanic. He said, :when you see this oxidation in wire, you can bet it has travel under sheathing along wire strains. Which result in increased resistance. When they see oxidation on wires. They don't bother testing resistance. They just replace.

I see: Some blue, some white, some just dirty looking oxidation. These are for the most part moisture, acid and or salt related. None where near coolant.

View attachment 4036995View attachment 4036997View attachment 4036996

View attachment 4036998

Did you get any pictures, that you care to post here?

I did not. However, I am absolutely certain that mine looked identical to the oily substance in shown in the pictures in posts #1 & #2 in this thread.

 

[2001LC]

Mine was soaked in ATF. I discovered it because it was destroying A/F sensors. It was a wild ride. Here is the complete story: Oil wicking into ECM - random A/F sensor codes P0171/P0174/P2195/P2197 - https://forum.ih8mud.com/threads/oil-wicking-into-ecm-random-a-f-sensor-codes-p0171-p0174-p2195-p2197.1322776/

Here is a picture of that thread.
View attachment 4037006

Wow! For some reason, you had supper capillary action, from A/T case. Climbing all the way to O2, then on to ECM! Must be 5 foot with 18" rise.
And still fresh looking red ATF. Possible clue, speed of your capillary action, was very fast.

I see you purchased the 82125-60651 transmission wire (Valve body wire harness). For your 08 GX470 w/A750a. Which is same harness as our 04-07 LX470 & LC.
Which is now our third P/N for that harness.
Did your VIN # indicate, that was the original, 1st sub or 2rd sub P/N?
100 series first P/N's, for transmission (to valve body) wire harness:
06-07: 82125-60651 sub2, 82125-60650 sub1, 82125-35150 original.
04-05: 82125-35130 original.
2003: 82125-60550 original.

Did you ever find any clue. As to why? So much ATF and got so far up wires and so fast? Like:
Over filling A/T. In-which-case, wires may have been constantly immersed in ATF?
Increase A/T case pressure, from clogged breather perhaps?
Mix of ATF types/brand additives, resulting in excessive foaming?
Perhaps vehicle used in very harsh environment (very Low and or High, OAT), result in wire sheathing expanding/loosening away form wires.
Anything?
Any theory?

I did not. However, I am absolutely certain that mine looked identical to the oily substance in shown in the pictures in posts #1 & #2 in this thread.

Statement from "Looked Identical" is supper helpful.

I've been digging into issue of capillary action through this wire harness. Whereas in doesn't look like ATF as @white_lx 's clearly is ATF. It very likely is just ATF.

It may be gel added to wires, to stop capillary action. Possible it broke down and ended-up in wire housing block, perhaps mixing with ATF:

I Asked AI: "Auto manufacturers use specialized anti-capillary (fluid-blocked) cables that incorporate a barrier-sealing compound, typically a grease-like filler or silicone gel, within the conductor strands to block fluid migration. The gel in the wires typically looks like a clear, translucent, or sometimes colored grease or silicone substance that fills all the tiny voids between the individual copper strands and the insulation:

Interesting same in both of our, 07LX.
Also interesting Toyota change P/N 3 times only in 06-07. Did they find issue

I found one picture of this wire housing block, clean & dry, on ebay. No grease. @white_lx , Perhaps you can confirm? New OEM 82125-60651 housing block, you used. Was dry (ne grease)?

Pic from ebay:
Wire Housings block on outside of A/T case, of transmission Wire 82125-60651 to VB. You can see eyelet for retainer bolt to case. No antioxidation grease.

Used form ebay main A/T wire harness 82125-60580. Wire housing block that connect to VB wire harness block (above). No antioxidation grease.

I have seen where one of the transmission locking wire blocks, on top of bell housing near starter. Did have a grease like substance. I presumed, was factory applied to block oxidation. But IDK that!

Here's the transmission main harness 3 wire housing block near starter. See one on Driver Side (DS) has grease in it:
Engine, DS on your left. Main Transmission Harness 82125- 60580

Bell housing. DS on you right

 

[Unrulykid]

As an unadulterated reference for you;

My 2002 LX470 has the 4 speed transmission. Currently about 112,000 miles. California car. Always serviced at Lexus by previous owner. Transmission works great, with no issues. This is the first time this connector has been opened since the vehicle was made. Opened it today to get a photo for you as reference… and to ensure that I don’t have this fluid wicking issue.

I understand that Toyota used a PAO based dielectric grease like NYOGEL 760G for these areas subject to fretting corrosion …

 

[white_lx]

Wow! For some reason, you had supper capillary action, from A/T case. Climbing all the way to O2, then on to ECM! Must be 5 foot with 18" rise.
And still fresh looking red ATF. Possible clue, speed of your capillary action, was very fast.

From A/T to ECM and then on to the A/F because A/F sensors happened to be at the same ECM connector.

I see you purchased the 82125-60651 transmission wire (Valve body wire harness). For your 08 GX470 w/A750a. Which is same harness as our 04-07 LX470 & LC.
Which is now our third P/N for that harness.
Did your VIN # indicate, that was the original, 1sr sub or 2rd sub P/N?

The original part # according to the VIN/Partsouq was 82125-60650 for the '08. It was superseded by the -60651, which is the one I used for the repair.

The problem does not seem to be limited to GX. I came across forum posts of the identical problems with FJ's, 4Runners and LX as well. Regarding the LX, there was a reply (#26 in that thread) by @KeepGoing about the same problem with a '06 LX470.

Did you ever find any clue. As to why? So much ATF and got so far up wires and so fast? Like:
Over filling A/T. In-which-case, wires may have been constantly immersed in ATF?
Increase A/T case pressure, from clogged breather perhaps?
Mix of ATF types/brand additives, resulting in excessive foaming?
Perhaps vehicle used in very harsh environment (very Low and or High, OAT), result in wire sheathing expanding/loosening away form wires.
Anything?
Any theory?

The A/T was not over-filled. I was the first owner to replace the ATF and I used original Toyota WS set to the correct level using the Toyota procedure. The breather was fine. After the repair, I set the ATF level again using the same procedure and the wicking has not re-occured.

The vehicle came with an extensive service record. Pretty sure it was a mall-cruiser and not used beyond where Corolla's normally go. But from what I read online, there are many vehicles with this problem.

I read forums posts where it was speculated that the cause for the wicking are the two temperature sensors that come as part of the transmission wire. I guess I could verify that by soaking them in ATF and observing the connector of the transmission wire that was removed (I kept the part). But it is more of an academic exercise. From everything that I read (and my own experience), the -60651 part fixes the wicking.

I've been digging into issue of capillary action through this wire harness. Whereas in doesn't look like ATF as @white_lx 's clearly is ATF. It very likely is just ATF.

By the time the ATF made it to the ECM, the fluid no longer had a red color. See the pictures in that thread.

I found one picture of this wire housing block, clean & dry, on ebay. No grease. @white_lx , Perhaps you can confirm? New OEM 82125-60651 housing block, you used. Was dry (ne grease)?

It was indeed dry. Other than the contamination with the ATF, there were no visual differences between the -60650 and -60651 parts.

Here is short video about a 2003 4-Runner with the same problem:

 

[2001LC]

As an unadulterated reference for you;

My 2002 LX470 has the 4 speed transmission. Currently about 112,000 miles. California car. Always serviced at Lexus by previous owner. Transmission works great, with no issues. This is the first time this connector has been opened since the vehicle was made. Opened it today to get a photo for you as reference… and to ensure that I don’t have this fluid wicking issue.

View attachment 4037889

I understand that Toyota used a PAO based dielectric grease like NYOGEL 760G for these areas subject to fretting corrosion …

Interesting.

Thanks, for posting the picture.

Toyota factory or shop adding dielectric grease, was my first though. So I searched and search for picture of early shots factory wire housing blocks, new part and used. I did not find any evidence of dielectric grease used in this spot. Not saying it wasn't, just I didn't find.

So I started this thread, to see what may pop up and how much of issue is this.
In 07LX I'm working, no history or indication and type of A/T service. That would account for gray goo being D-grease.

I searched for 02 main transmission wire harness 82125-60382 sub, 82125-60380 original P/N. Looking for picture of the same angle on wire housing block you show from your 02 LX. Didn't find helpful.

However I did find, the one it plugs into. A used wire transmission (mounts on case and connects to valve body solenoids) 82125-60310
Just one used pictures not as good as getting a new to inspect. But I don't see any grease in this one.

From A/T to ECM and then on to the A/F because A/F sensors happened to be at the same ECM connector.

The original part # according to the VIN/Partsouq was 82125-60650 for the '08. It was superseded by the -60651, which is the one I used for the repair.

The problem does not seem to be limited to GX. I came across forum posts of the identical problems with FJ's, 4Runners and LX as well. Regarding the LX, there was a reply (#26 in that thread) by @KeepGoing about the same problem with a '06 LX470.

The A/T was not over-filled. I was the first owner to replace the ATF and I used original Toyota WS set to the correct level using the Toyota procedure. The breather was fine. After the repair, I set the ATF level again using the same procedure and the wicking has not re-occured.

The vehicle came with an extensive service record. Pretty sure it was a mall-cruiser and not used beyond where Corolla's normally go. But from what I read online, there are many vehicles with this problem.

I read forums posts where it was speculated that the cause for the wicking are the two temperature sensors that come as part of the transmission wire. I guess I could verify that by soaking them in ATF and observing the connector of the transmission wire that was removed (I kept the part). But it is more of an academic exercise. From everything that I read (and my own experience), the -60651 part fixes the wicking.

By the time the ATF made it to the ECM, the fluid no longer had a red color. See the pictures in that thread.

It was indeed dry. Other than the contamination with the ATF, there were no visual differences between the -60650 and -60651 parts.

Here is short video about a 2003 4-Runner with the same problem:

Supper helpful and a great write up and response. Thank you!

Especial that new wire housing block in 82125-60651 was dry (no D-grease).

So we've evidence, wire housing block, comes dry. No actual evidence Toyota add grease. Note: not found in FSM either, but still searching!

I'm asking, some of my Toyota and Lexus parts guys. To look for TSB, on issue of capillary action and this wire harness. Possible we'd see a statement the 3rd sub P/N corrects the issue.

Anyone have a TSB on this wire harness that penetrates the A/T case?

 

[Rednexus]

I replaced the transmission-side of the harness in my 2007 GX470 (part number 8212560651). The part is readily available from Toyota for around $60. It didn't have any obvious wicking issues, but I was getting P2759 codes and wanted to eliminate every variable. The transmission started shifting quite a bit better after replacing the harness (it had a weird "hop" in the shifts that went away), so it's totally possible the harness was degraded with increased resistance even if no fluid was in the connector. And, the P2759 code went away. So my recommendation is to replace the harness if one is having any issues on a higher-mileage/older A750F.

The harness part has been updated by Toyota (at least since 2007) and wasn't an exact match to the original, so it can be easy to hook up the solenoids wrong. Good photographs of the old harness - before you remove it - are recommended.

 

[2001LC]

Seems, many non 100 series, have been seeing this wire harness issues More so than we in the 100 series, to date!

Are we likely to see increase incidence, as fleet ages. I think so!

In my deep-dive. I've found, many non 100 series transmission Valve Body's, having seeing issues of wear.

It was suggested, those other makes and models, the A/T fluid runs hotter. I don't work any other than 100 series and a few 200 series. So I can't say anything with regards to their ATF cooling system or ATF temp they run at.

Except to say; In the 200 series A/T fluid, does run hotter. First time I monitored a 200 series A/T fluid temp, driving. I became, very concerned. It was after a full flush, on its test drive. Also worth a note: The ATF I flush out of 200 series. Comes out very dark. Much more so than our 100 series, for given mileage. But, it turns out. It's normal for the 200 series. Their A/T fluid runs ~200f just normal city HWY driving. Even hotter pulling loads, off road and in high OAT conditions.

In deep-diving into the valve body (Aisin 8850) of the Aisin-warner A750f. I found in other makes and models, it's used in. They see a lot of valve body issue with wear. I've also talk with some of the top valve body customizer and stock rebuilders in the USA, in past few weeks. They don't see many 100 series. But they do see a good amount of 200 series valve bodies. It what they call, common wear issues, found in the Aisin Valve body.

Perhaps this wire is one of the of the factors in valve body wear. I'm just spit-balling/theorizing without all that facts and only a little real data:
Let say heating & cooling cycles, effects the wire in few ways. The more heat and temp differential. The more the effect;

1. Expansion & contraction. Resulting in opening the micro spaces between wires strains and each wire's sheathing. Same for the bundle of ~11 wire in the wire housing harness.
2. Each heating and cooling cycle. Compress out, some of whatever substances is in wires. Pumps it out, one might say.
3. The more a wire housing ages. The more the sheathing would thin/shrink. Again, increasing spaces between sheathing. Heat and cold cycles would speed up aging.
4. Heat would also thins the ATF.
5. Differences in heat along wire housing, would result in great migration (thermocapillarity) from hot to cooler wire.
6. Contamination within the wire begins, as ATF flows in. At first this may be very minor increase in resistance. Resulting in, minor shifting issue! Not perceptible by driver.
7. Let also go ahead and assume, AI was correct. Manufacture added a substance in wires, to block capillary action. But due to above age related derogation and expansion and contact along with capillary action. This substance push out, into wire housing block, even some into A/T case. Thios may be, the grease we see in some wire housing blocks.
8. This supposed substances, gets deposed in the wire housing block. At first thick and a light color.
9. Next ATF enters the wire housing block. It results, not only in increased resistance. But cross current, across connect pins of wires. Goo (substance & ATF mix), is then seen in wire housing block.
10. A/T TCM/ECU and solenoids now get mixed signals. Shift issue, may then become more apparent. Depend on speed of this whole action/reaction. Speed/age of occurrence, could be a factor of, temp swing and severity.
11. Mix in wire housing, at first blocks capillary action past hosing. As a plug. But in time, as it thins. Capillary action continues up main transmission wire harness, heading toward other wire housings, O2's, A/F, TCM/ECU, etc.

That during the early stages, only minor resistance in wires. Resulting almost imperceptible shifting issues. Above normal wear, for miles and use, begins in A/T. This wear would increase insoluble in ATF, above normal level for the mileage. Insoluble increase clutch plate's, ability to hold. But also increase wear throughout A/T. Which valve body would for sure, be high wear. More than expected for mileage.

As shift condition worsens, likely, so would insoluble in ATF.

Checking and replacing this wire harness and sending a sample of ATF, out to Blackstone. Is something we may need to start doing as a PM. If analysis report of ATF sample, show higher than normal insoluble. 12 qt ATF flush, ASAP. Even adding inline filter temporarily. Rested ATF few thousand miles or if any shift issue come back. May be a good course of action, we all need to do.

AI ?
"Is oil capillary action, affected by heat along strand wire in sheathing. In that if heat high at lower end wire is in oil, and temperature drop lower the further up the wire. The more oil wants to climb to cooler wire"

Yes, a temperature gradient along a wire can affect oil's capillary action, and the oil generally migrates towards the
cooler region. This movement is driven by a phenomenon called thermocapillarity (Marangoni effect), which is related to how temperature impacts the physical properties of the oil.

Understanding the Forces

• Capillary action is the movement of a liquid in narrow spaces due to intermolecular forces like cohesion (liquid molecules sticking to each other) and adhesion (liquid molecules sticking to the solid surface). It depends on the liquid's surface tension and how well it wets the surface.
• Temperature's effect is crucial: as temperature increases, both the surface tension and viscosity of the oil decrease.
• The thermocapillary effect arises because the cooler end of the wire has higher surface tension than the warmer end.

How the Migration Works

1. Surface Tension Gradient: The difference in temperature creates a gradient in surface tension along the oil-stained wire.
2. Marangoni Flow: The liquid is pulled towards the area with higher surface tension (the cooler, upper section) by the resulting force.
3. Overall Movement: This force can work with or against the standard capillary forces and gravity, but the net result in such scenarios is often a migration of the oil film or droplets toward the cooler region to minimize the overall surface free energy.

Why It Matters
Understanding this effect is vital in industrial and automotive applications where cables are exposed to oils and temperature variations. This migration can lead to fluid wicking into connectors or control modules, causing damage and system failure. Using anti-capillary wire or blocking the pathway with solder can prevent this problem.
Would you like to learn about specific methods to pre

That looks like water & engine oil to me.

Good observation. Although that in wire housing block, perhaps a bit more translucent than oil & water mix.
Looks a bit like, PB Blaster Long lasting Undershield. Which I'd sprayed only months before my first very notable shifting issue. My first though, was electrical resistance issue in wiring, due to this spray. So I looked. Nope, I hadn't gotten any on, wires or on wire housing blocks.

Examples of engine oil and coolant (Toy SSL) mix by churning and heat

Example of grease and water mix

 

[2001LC]

The original part # according to the VIN/Partsouq was 82125-60650 for the '08. It was superseded by the -60651, which is the one I used for the repair.

The 06-07 LC & LX original 82125-35150, 2nd -60650, 3rd -60651.
The 04-05 LC & LX original -35130 I don't see any updates. "May" update when ordering in VIN used. IDK, but I'll ask.
The 2003 LC & LX original -60550. I don't see any updates. "May" update when ordering in VIN used. IDK, but I'll ask.

Toyota has been updating the S.A.I pump filter. I've now seen 3 different designs of the filter. IMHO all 3, will fail. I do think, each newer version will last longer.

I hope this is not case with this transmission wire. But we'll be well service, to keep eye on even this newest 82125-60651 transmission wire. By looking in its housing block and watch for further P/N changes.

The problem does not seem to be limited to GX. I came across forum posts of the identical problems with FJ's, 4Runners and LX as well. Regarding the LX, there was a reply (#26 in that thread) by @KeepGoing about the same problem with a '06 LX470.

Perhaps all A750f original, transmission wire has this capillary issue. One of my hopes with this thread. Is we see if a patterns emerge.
So fax we've:
2- 07LX A750f. With GOO, in the 82125-35150 wire housing block. Shift issues.
1- 08GX A750f. With ATF, in the 82125-60650 wire housing block and much further down stream. O2 issue.
1- 07GX A750f. No ATF, in the 82125-***** wire housing block. P2759 corrected w/new wire -60651
1- 04LX A750f with oxidation in the 82125-35130 wire housing block. Shift issues.
1- 04 4runner A750? (video). AFT, in the 82125-????? wire housing block and much further down stream. O2 issue.

I- 02LX A343f with what appears to be clean Dielectric grease inside wire housing block,. In low miles, clean, with no report of any transmission service. No report of any issues.

I read forums posts where it was speculated that the cause for the wicking are the two temperature sensors that come as part of the transmission wire. I guess I could verify that by soaking them in ATF and observing the connector of the transmission wire that was removed (I kept the part). But it is more of an academic exercise. From everything that I read (and my own experience), the -60651 part fixes the wicking.

Interesting, there was speculation, cause was from the "two temperature sensors" wires:

The 98-02 A343f, has only 4 wires. The one temp sensors, wire just plug onto. Just like wire plug on all solenoid. So far in this thread. No reports of ATF in A343f transmission wire housing block.

The A750f. Has 11 wires. Two of the wires, have temperature sensor built on end. That is to say; they're part of wire end. They fit up in valve body, and seal with O-ring. Each has a hefty bracket retaining them. They obviously have ATF under pressure behind them. I noted, a good amount of fluid, from their port, as I removed them. So they ATF, behind them with static pressure engine off, continues pressure engine/transmission running. The other 9 wires, basically just get slashes or wash-over ATF. They sit well above level of pan. So make sense, temp wire would be the subject to the most and capillary action.
Temperature sensors A/T #1 & A/T #2 (red arrow) of the A750f/e Aisin-Warner 8850 Aisin valve body.

 

[Unrulykid]

Update on 2002 LX 470

As an unadulterated reference for you;

My 2002 LX470 has the 4 speed transmission. Currently about 112,000 miles. California car. Always serviced at Lexus by previous owner. Transmission works great, with no issues. This is the first time this connector has been opened since the vehicle was made. Opened it today to get a photo for you as reference… and to ensure that I don’t have this fluid wicking issue.

View attachment 4037889

I understand that Toyota used a PAO based dielectric grease like NYOGEL 760G for these areas subject to fretting corrosion …

Update:

The 5 wire female transmission electrical connector is clean, and has clean looking factory applied grease with no indication of fluid ingress. I had previously attempted to get a photo of the 5 wire male connector mounted to the transmission body. But there is very little room and I could not get my phone up in there to take a picture. This was the best I had using a mirror... Lousy photo, so I did not post it previously. Looks kinda dark and wet in there.

Today, I put the borescope up in there… It looks wet from ATF wicking up the internal wiring into this male electrical connector that is mounted on the outside of the transmission.

So… the update is; this transmission works perfectly without any issues. But I believe it does have the ATF wicking issue… it simply has not presented as a functional problem as of yet. The ATF has only made its way into the bottom of the male connector mounted on the outside of the transmission. No sign of ATF in the female connector.
You would never know that this transmission was developing a problem by an external examination with great scrutiny or by driving the vehicle. You could only tell by opening the transmission electrical connector and looking in there with a scope.