Transmission oil temperature problem.

[Cañonero]

Hello.

As I told you before, I broke the transmission of my HDJ81 about two year ago and I had to rebuild it.

It was rebuilt by a local automatic transmission specialist and it worked fine, the only problem I had was that I had the A/T oil temperarture light on during a trip in the Morroccan desert, but I thought it was normal in that conditions.

Anyway, after that I installed a heavy duty transmission oil radiator, the one shown in the picture:

And, last week, I installed a transmission oil temperature gauge purchased at wholesale automatics in Australia: Wholesale Automatic Transmissions


I've been checking the temperatures in several circumstances and the results are worrying:

In the highway, it stays really cool (140ºF-170ºF), but as soon as I start driving in mountain roads (I live in a very mountainous place) the temperature starts to rise very quickly. It even reached 270 ºF driving very fast in a mountain pass.

Firstly, I thought that the radiator I have installed doesn't work well when the air flow is not strong enough, but then I started to see that, when going in overdrive, the temperature goes down and, as soon as the 2nd or 3rd gear are engaged, it becomes hot really quickly.

I did an experiment: I went uphill during 10 miles in overdrive with the cruise control set at 50 mph. The maximum temperature reached was 185ºF.

Then I drove back down to the first point again and did the same track again with the cruise control at 50mph again, but in 3rd gear. At the end of the track, the temperature was 245ºF.

My theory is that the torque convertor is not locking up properly in 2nd and 3rd gear (in overdrive is always locked I think), or maybe is slipping too much.

What do you think? I think these temperatures are way too hot, specially considering I run a heavy duty radiator and that it was freezing outside.

Do you think the extreme valve body kit from wholesale automatics would be a solution or would I need a complete transmission rebuilt?

Wholesale Automatic Transmissions

A friend advises me to install an extra transmission oil radiator, but I don't think that would solve the problem.


Any advises?

 

[Cruiser Jimmy]

What transmission is in the HDJ, an A440F or the A442F? How many miles on the vehicle?

Your 'A/T Oil Temp' light comes on at 305º and goes off at around 120º, IIRC.

From the way you describe it sounds like while in 3rd gear the overdrive direct clutch is slipping which is causing the heat (if you're not in lockup.) Remember, the Torque Converter is multiplying the torque from the engine rotation, so if the lockup is not engaging then you could be heating up those clutches.


IMHO.




BTW, the tube style oil radiators are so what less efficient than the sandwich plate style radiators.

 

[elhombre]

Does your fluid smell bad/burnt ? Do you use synthetic fluid? Heat really kills the fluid and synthetic is the way to go if you are in the upper hot range. I have always been told that the first thing you do when starting to have transmission problems is to change the fluid to see if the problem persists. Is your truck fully loaded down with a bunch of add-ons that make your truck real heavy? Finally, do you use sythetic oil in the transfer and differential cases? Sythetics do work much better in the cases and lower the temperature in them also. Just some ideas to ponder.

Driving in sand is one of the hardest conditions for transmissions and engines. Usually, you are driving slow and the engine is at low RPMs so it is not moving much air. I have heard that if your truck has any cooling problems, driving in sand will bring them out.

 

[Cañonero]

What transmission is in the HDJ, an A440F or the A443F? How many miles on the vehicle?

Your 'A/T Oil Temp' light comes on at 305º and goes off at around 120º, IIRC.

From the way you describe it sounds like while in 3rd gear the overdrive direct clutch is slipping which is causing the heat (if you're not in lockup.) Remember, the Torque Converter is multiplying the torque from the engine rotation, so if the lockup is not engaging then you could be heating up those clutches.


IMHO.




BTW, the tube style oil radiators are so what less efficient than the sandwich plate style radiators.

My transmission is the A442F, the first version (hidraulic).

I think the problem is that the lockup is not engaging. When should it engage, and is there any way to notice it?

I don't know how to make the differnce between the tube oil radiators and the sandwich plate style. What type is mine?. Could you post a link to a picture of both types?

Thanks a lot

 

[Cañonero]

Does your fluid smell bad/burnt ? Do you use synthetic fluid? Heat really kills the fluid and synthetic is the way to go if you are in the upper hot range. I have always been told that the first thing you do when starting to have transmission problems is to change the fluid to see if the problem persists. Is your truck fully loaded down with a bunch of add-ons that make your truck real heavy? Finally, do you use sythetic oil in the transfer and differential cases? Sythetics do work much better in the cases and lower the temperature in them also. Just some ideas to ponder.

Driving in sand is one of the hardest conditions for transmissions and engines. Usually, you are driving slow and the engine is at low RPMs so it is not moving much air. I have heard that if your truck has any cooling problems, driving in sand will bring them out.

My fluid is two weeks old and its fully synthetic. They even used a machine to replace all the fluid, not only a flush, as usual, so 100% of the fluid is new and fully synthetic. The fluid in the transfer and differentials is synthetic as well.

As you say, sand is the hardest condition to keep the transmission cool. So, if it's running so hot now on the road, it would literally burn on the sand.

 

[Cañonero]

By the way, I forgot to mention that the mechanic avoided the little transmission oil radiator that goes inside the engine water radiator. He said that it doesn't cool much and that there is a risk of a water leak into the transmission that would damage it.

Do you think he is right?

 

[Tools R Us]

IMHO the factory cooler that comes in rigs with the towing option work very well, even when stressed in desert climate. My guess is the factory cooler is much more efficient than the one that your running. The general rule with coolers is cross flow plate type coolers (like the stock one) are most always more efficient than tube type and surface area is very important, wider, taller and thinner are always good things. If it were my rig, would source a factory setup from Toyota or a wreck.

Some pix of it in this thread;

https://forum.ih8mud.com/80-series-tech/19299-transmission-fluid-exchange-writeup-2.html

 

[nicholas]

Those temperatures seem pretty high. For reference, when I drive through deep snow with a fully loaded down cargo or up steep mountain grades at slow speed (and several PSI of boost from the S/C) my trans has never got above 175*. My sender is not right at the transmission port, but actually a couple feet forward on the cooling lone just before it enters the trans cooler. However, I don't think the fluid could cool significantly in that couple of feet.

 

[nicholas]

By the way, I forgot to mention that the mechanic avoided the little transmission oil radiator that goes inside the engine water radiator. He said that it doesn't cool much and that there is a risk of a water leak into the transmission that would damage it.

Do you think he is right?

No, I think that might be the problem. AFAIK, I have never heard of water leaking into the trans, but I'm sure it could happen if the radiator was damaged. Toyota makes pretty dang good parts.

 

[wussyPup]

My transmission is the A442F, the first version (hidraulic).

I think the problem is that the lockup is not engaging. When should it engage, and is there any way to notice it?

I don't know how to make the differnce between the tube oil radiators and the sandwich plate style. What type is mine?. Could you post a link to a picture of both types?

Thanks a lot

Hi, I have an 1990 HDJ81 with the early style hydraulic A442F. They are not designed to lockup in 3'rd gear; only D. So, when working hard in 3'rd gear they will generate a lot of heat. Rodney sells a modified valve body designed to lockup in 3'rd gear as well as in D.

With the 1HD-T and stock A442F we have a challenge with heavy loads on long hills. If we drive in D, the torque converter can lockup reducing ATF temp but the EGTs can rise to fatal levels. Driving in 3'rd to increase engine RPM and reduce engine load will let the EGTs drop to safer levels, but as you have experienced, can overheat the A442F.

General opinion is that the warning light on the A442F comes on way too late; it comes on after heat has started damaging the tranny. At first sign of the warning light, pull over, shift to N, open the hood and increase engine RPM to draw as much air as possible over the cooler.

Aux tranny coolers have a BTU rating to measure how much heat they can dissipate. You can search online to see if you can find a similar designed and sized cooler as yours to find the BTU rating (ignore the GVW rating; it is marketing BS). The cooler I installed is rated at 34,000 BTU; described here TRU-COOL

G'luck, -Steve

 

[Tools R Us]

By the way, I forgot to mention that the mechanic avoided the little transmission oil radiator that goes inside the engine water radiator. He said that it doesn't cool much and that there is a risk of a water leak into the transmission that would damage it.

Do you think he is right?

I don’t agree, at all! The coolant heat exchanger has two important purposes. First it’s a pretty powerful cooler. Second it works as a thermostat, regulating the fluid temp. The proper setup is circulating the fluid first through the air cooler then the water cooler. Studies have shown that wear numbers are actually higher when the trans is run with cold fluid, than when marginally overheated. On cold start and cold weather the coolant heat exchanger helps in bringing the fluid up to operating temp sooner, reducing wear and improving drivability.

There is a slight risk of it failing and leaking into the coolant, but it's rare. IMHO they are very reliable and their benefit far outweighs the risk.

 

[Cañonero]

Thank you all.

So the general opinion is that it's been a bad idea to avoid the stock cooler through the engine radiator. I'll ask him to reconect it again.

Anyway, that may lower the temps a little bit but I don't think it will solve the problem.

The root of the problem seems to be, like wussyPup says, that the early A442F transmission doesn't lock up in 3rd gear, but, anyway, I've read the temperatures of other people with the same transmission and don't reach as high temperatures as I do.

Do you think Rodney's valve body kit would solve the problem?

I'm also trying to choose an apropiate transmission cooler. A friend of mine is going to order an intercooler from frozenboost, and I think I could take the chance to share the shipping costs with him and order one of frozenboost's universal fluid radiators like this:

Oil Cooler

Does it seem to be a good quality transmission cooler?

 

[CJF]

Thank you all.

So the general opinion is that it's been a bad idea to avoid the stock cooler through the engine radiator. I'll ask him to reconect it again.

Anyway, that may lower the temps a little bit but I don't think it will solve the problem.

The root of the problem seems to be, like wussyPup says, that the early A442F transmission doesn't lock up in 3rd gear, but, anyway, I've read the temperatures of other people with the same transmission and don't reach as high temperatures as I do.

Do you think Rodney's valve body kit would solve the problem?

I'm also trying to choose an apropiate transmission cooler. A friend of mine is going to order an intercooler from frozenboost, and I think I could take the chance to share the shipping costs with him and order one of frozenboost's universal fluid radiators like this:

Oil Cooler

Does it seem to be a good quality transmission cooler?

1) Let's be clear here guys: The "early A442F" is NOT an A442F, it's the A440F (used in US '88-92 Cruisers, among other applications). Edit: Incorrect info. See corrections in later posts.

2) As others have said, you really should go back to the cooler in the radiator, as well as the stock (in the US at least) or equivalent cooler in front of the rad. Until you do, I'm not sure you'll ever know whether or not the tranny itself is the problem.

3) I don't know whether Rodney's Extreme Valve Body will "solve the problem", but it does have 3rd gear torque converter lockup(so should run noticeably cooler in that gear), if I recall correctly.

4) Deal with this SOON! Heat KILLS transmissions. I think I'd change fluid immediately after it having gotten so hot.

Cheers,

Curtis

 

[CJF]

I have never heard of water leaking into the trans,

For the record, we've seen at least two instances of that here on the forum.

As you said though, nowhere near a common enough issue to bypass it; it serves a purpose.

Curtis

 

[e9999]

if somebody finds a good writeup on these "locking up" issues for the converters, I'd like to learn a bit about it. I see these jumps and decreases of rpm when I up/down shift and would like to figure out a bit more what that really means.

 

[Cruiser Jimmy]

Yes, the one you linked is sandwich plate(cross flow plate) style radiator that is more efficient. (Theory is that when you flatten out a fluids surface, you increase the rate of thermal transfer.
Pup is right, unmodified the lockup is not designed to engage in 3rd gear, only when in 'D' and the speed is between 47~55 mph.
You can notice the lockup 'engage' by one of two methods.
First, by the sound of the engine shifting down in rpm's from O/D then into lockup.
Second, by watching the rpm's on the tech shift down from O/D then into lockup.

This can be felt/seen when you're on the highway and accelerate up to cruising speed.
You should be able to see and hear four distinct down shift in the rpms.
1st to 2nd: 1st down shift
2nd to 3rd: 2nd down shift
3rd to O/D: 3rd down shift
Lockup while in O/D and above 47~55 mph: 4th down shift

 

[Cruiser Jimmy]

4) Deal with this SOON! Heat KILLS ......

Agreed!!

Check the fluid to make sure it's NOT black, dark brown, dark dark red, and try to smell it. If it smells burnt and it's any of the of fore mentioned colors, then it's bad.

Normal fluid should be red or a slight variation of red. And it should not smell burnt.

 

[Cruiserdrew]

So does the Rodney valve body alone allow 3rd gear lock up in the A440, or does the entire transmission need to be rebuilt? It seems like all of the heating problems occur when driving in 3rd gear with a load (like a hill). I sort of like the A440 for it's simplicity, but this one thing seems to be a major weakness, as 3rd gear up hill with a load is a very common scenerio.

On the later transmissions, at least on the A343, there is a 3rd gear lock up-if you take the overdrive off and run in 3rd gear, it will lock. If you leave the overdrive on, and it shifts to third, it doesn't seem to lock. Kind of curious behavior. I assume the A343 in the early 100 series would be similar.

I noticed in the link to the TruCool tranny coolers, it says to plumb the cooler downstream from the radiator, which is how I did the one in my A440, but Tools said in his post that before the radiator cooler would be preferred? It probably only matters in a really cold climate.

 

[wussyPup]

1) Let's be clear here guys: The "early A442F" is NOT an A442F, it's the A440F (used in US '88-92 Cruisers, among other applications).

Toyota calls the ATM fitted to early JDM HDJ81s like Cañonero's and mine an A442F. I don't know why.

When dealing with Rodney for a replacement; he referred to them as the "early A442F" to differentiate them from the later ones with more electronics.

 

[Cañonero]

Also, Rodney told me in one of his emails, that the hydraulic A442F was an important improvement over the A440F.