A343F Trans & ScanGauge II what are your temp readings? (1 Viewer)

[geanes]

Towing my small trailer today and on a steep incline here in Austin I saw 250 on the trans temp! I was stuck in bumper to bumper traffic climbing a hill at 5mph in 93 degree air temp. Got to the top and temps dropped back down to 200 then 180 pretty quick. Never seen the trans temp climb that high before. Very scary. Hopefully no damage. Checked fluid levels and they are fine. Fluid still appears red on the dipstick (98 LX). Pulling the trailer at highway speeds generally results in a trans temp of 170

 

[abuck99]

250 F is very high, especially for a 100.
Fluid life deteriorates exponentially above 200 F. Worth looking into.

How long since last fluid exchange?

 

[geanes]

250 F is very high, especially for a 100.
Fluid life deteriorates exponentially above 200 F. Worth looking into.

How long since last fluid exchange?

It was done just last year with Toyota Fluid. 30k miles ago. Kinda scared about what I’ll see when I go to Colorado this summer. They have hills there that we don’t have in TX.

 

[trdcorolla]

Was your overdrive off?

 

[flintknapper]

Was your overdrive off?

At the speed he was going (5mph) he should have always been 1st gear, no overdrive going on there.

Under no conditions, towing or otherwise have I had my trans temp exceed 180° F.

250°F is way up there IMO and definitely something to look at.

 

[flintknapper]

It was done just last year with Toyota Fluid. 30k miles ago. Kinda scared about what I’ll see when I go to Colorado this summer. They have hills there that we don’t have in TX.

Are these the codes you used to set your Xgauge (trans temp)?

TXD: 686AF101B4

RXF: 044105B40000

RXD: 2808

MTH: 00090005FFD8

 

[geanes]

Are these the codes you used to set your Xgauge (trans temp)?

TXD: 686AF101B4

RXF: 044105B40000

RXD: 2808

MTH: 00090005FFD8

Yes

 

[geanes]

At the speed he was going (5mph) he should have always been 1st gear, no overdrive going on there.

Under no conditions, towing or otherwise have I had my trans temp exceed 180° F.

250°F is way up there IMO and definitely something to look at.

Correct. I was in 1st gear. My trailer is only 800lbs. Checked fluid again and it’s red and at full level.

 

[geanes]

For reference....rig typically fluctuates between 136-140 cruising and 156-170 under acceleration. I’ve noticed she usually hovers around 174 when towing. 145-150 idling.

 

[hidesertwheelin]

Up to 150 climbing up to Flagstaff from Kingman in the heat (90 deg +/-), and 120 the entire way home.

 

[geanes]

Up to 150 climbing up to Flagstaff from Kingman in the heat (90 deg +/-), and 120 the entire way home.

343 transmission? My temps are much higher.

 

[hidesertwheelin]

343 transmission? My temps are much higher.

Yep, 2000 LX470

 

[abuck99]

Youre lucky to have the A343- makes it easy to check on condition and level. Those regular temp numbers posted sound typical. I might do a drain and fill ahead of your Colorado trip (3-4qts) to refresh the fluid. Climbing trails puts a load on torque converter resulting in a lot of heat.

You might inspect the cooler for debris (grass,dirt,mud) and also the front lower section of the radiator for any build up of debris. Water crossings,
mudholes have a lot of silt and junk that can block cooling.

Is the fan clutch good and the aux fan working properly.

 

[geanes]

Yep, 2000 LX470

Impressive. Guess I need to start tracking down what is causing my elevated temps. Fluid is full and appears in great shape (bright red). Wondering now if the electric fan for the transmission is not kicking on.

 

[geanes]

Youre lucky to have the A343- makes it easy to check on condition and level. Those regular temp numbers posted sound typical. I might do a drain and fill ahead of your Colorado trip (3-4qts) to refresh the fluid.

You might inspect the cooler for debris (grass,dirt,mud) and also the front lower section of the radiator for any build up of debris. Water crossings,
mudholes have a lot of silt and junk that can block cooling.

Excellent points. I do a LOT of off-road travel in dusty areas with many water crossings (typically no more than hub deep). Figure I need to check the electric fan on the transmission cooler at the front.

 

[flintknapper]

Up to 150 climbing up to Flagstaff from Kingman in the heat (90 deg +/-), and 120 the entire way home.

Yeah, I'm typically 125-130ish on the highway (not towing). I've seen 160°F in stop and go traffic in town, dead of summer....but it quickly comes down once I get up some speed. I'm usually no more than 140° F just going around town in the summertime.

Pretty much the same temps for both A343F trannys (LX4170 and 80 series L/C). I am always amazed at how cool these trannys run.

I have increased the line pressure on my 80 series (310K miles now) but not the LX470. I have about 217K on the LX. Whenever I get around to dropping the pan on the LX I will probably bump up the line pressure on it as well.

 

[abuck99]

Yeah, I'm typically 125-130ish on the highway (not towing). I've seen 160°F in stop and go traffic in town, dead of summer....but it quickly comes down once I get up some speed. I'm usually no more than 140° F just going around town in the summertime.

Pretty much the same temps for both A343F trannys (LX4170 and 80 series L/C). I am always amazed at how cool these trannys run.

I have increased the line pressure on my 80 series (310K miles now) but not the LX470. I have about 217K on the LX. Whenever I get around to dropping the pan on the LX I will probably bump up the line pressure on it as well.

Good info- do you mind giving more detail on how to of increasing line pressure and why it could help here.

 

[flintknapper]

Good info- do you mind giving more detail on how to of increasing line pressure and why it could help here.

On the 80 series...its a simple matter of adjusting the Primary Regulator Valve tension on your Valve Body (no tools required). I have NOT looked at the A343F on my 100 series to see if this feature carried over (past '97)..but if it did, the same could be accomplished. Push in on the PRV cap, push up slightly on the flat detent keeper, rotate the cap to the desired position, lower the keeper, done.

The 'purpose' (do this at your own risk) is to help facilitate firmer clutch engagement across the board without the need to install a trans kit. Faster, more positive shifts (engagement) is an effort to increase the life of the transmission's friction discs (assuming they are still in good condition).

This will NOT appreciably decrease operating temperature...so don't do it for that reason.

The majority of the heat created in the transmission is from the Torque Converter. Anytime the TQ clutch is not locked up...it is creating a lot of heat. This would also be true if friction discs were slipping or a TQ clutch slips. But neither of those last very long when they get that worn.

 

[abuck99]

On the 80 series...its a simple matter of adjusting the Primary Regulator Valve tension on your Valve Body (no tools required). I have NOT looked at the A343F on my 100 series to see if this feature carried over (past '97)..but if it did, the same could be accomplished. Push in on the PRV cap, push up slightly on the flat detent keeper, rotate the cap to the desired position, lower the keeper, done.

The 'purpose' (do this at your own risk) is to help facilitate firmer clutch engagement across the board without the need to install a trans kit. Faster, more positive shifts (engagement) is an effort to increase the life of the transmission's friction discs (assuming they are still in good condition).

This will NOT appreciably decrease operating temperature...so don't do it for that reason.

The majority of the heat created in the transmission is from the Torque Converter. Anytime the TQ clutch is not locked up...it is creating a lot of heat. This would also be true if friction discs were slipping or a TQ clutch slips. But neither of those last very long when they get that worn.

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View attachment 1982544

Thanks- makes sense. I'm in the A750 camp, but wanted to know more about the process and result. I think the A750 is configured differently and the adjustment is not as simple.

 

[flintknapper]

Thanks- makes sense. I'm in the A750 camp, but wanted to know more about the process and result. I think the A750 is configured differently and the adjustment is not as simple.

PRV set up is the same for the 750 and Accumulator pressure is also adjustable. But to some degree the ECM might over-ride the adjustments in certain situations...since it uses a temp sensor to modify shift pressure.