Transmission Fluid Flow Rate through Radiator problem?

sure it is engaging. The lockup clutch is a mechanical clutch and is used to increase fuel mileage by eliminate torque converter slippage. If the lockup clutch is engaged (on most vehicles only in the highest gear) there should be little heat generated by the transmission.

inefficient torque converter. On long highway drives this should not happen if the torque converter lockup clutch is working.

Thanks Mike, Your comments sound exactly like one of the things the tranny shop found wrong 6+ months ago when they rebuilt the TC and tranny.

So I will ask them about this when we do our test drive after we put in the new radiator.

Thx Dave-in-Denver

Dave,

I don't have time to read over all of the messages in this thread, but I will chime in anyway, possibly adding nothing of importance...

I would like to know what you mean by "overheats". Do you mean that the trans temp light comes on at a certain point in your drive?

If so, I would be suspicious of the ATF level. If it is a hair too high in a A340F transmission/transfer unit, the fluid will readily aerate and cause that symptom. I would also be suspicious of what fluid additive a trans shop uses. They are often not as knowledgeable about transmission practice and theory as one would expect.

The original equipment aux cooler is very small, but it is adequate for any use I have run across. One problem with it is the location; a careless butcher can easily rack the left front lift arm on it and crush it trying to lift the vehicle. Has this cooler been bypassed in favor of an aftermarket one? If so, is the aftermarket unit inline with the airflow created by the mechanical fan?

I do agree that your original flow specs through the radiator cooler sound low, but that is a guestimate based on other similar experiments I have done at work, not your exact test.

Toyota MDT in MO

Hi Toyaota MDT,

I have inserted comments.

Yes... the tran temp light comes on. When doing 60+mph for about an hour.

Yes we found that we were way over filled... about 1.5 inches over the high mark. And yes a Toyota guy told me that too much fluid would aerate the t-fluid leading to overheating. I told this to tranny shop... was certainly unhappy that his guys overfilled the tranny but was skeptical that overfilling would cause tran temp light issues at just 60mph. So he did some checking and found the raidator had low t- fluid flow.

I do not know what t-fluid product they use. I was not in a position to have an opinion then... but now I know that what the Toyota guy told me; Dex2 is what that 1993 4Runner tranny was designed for... Dex3 replaced it a long time ago and on "really long multi-hour drives there is sometimes a problem". He suggested Texaco havelin AFT as most problem free product.

My 93 4Runner just had radiator t-fluid cooling. I had a shop put in an aux cooler a few years ago when I first noticed tranny waring signs. Size? I let the shop pic it out and they located it above the skid plate... no extra fan.

So thanks for your comments/questions... all things I will cover the tranny shop owner on Monday.

Thx Dave-in-Denver

95 4Runner, V6 3L, Auto, 4x4. I had a trans overheating problem also. After a heated discussion with my dealerships service manager, where I told him that my trans was overfilled and I thought that was my problem, he called Toyota. The fix was to check and make sure the trans was not overfilled. It needs to be checked after idling for 15 minutes. If it's overfilled it will cause the clutches to slip and overheat. On my last service they had overfilled it. They changed the fluid and filled it to the correct level and the problem went away.

Ron

Ron

Hi Ron, I think you are right... glad to have found someone who has the same picky tranny. If tranny fluid level was spot on... may never have found or noticed the poor flow problem.

The overfilled tranny was an important part of the problem. Then layer onto to that Dex2 vs Dex3 issue, then finding my radiator had restricted flow in it t-fluid section. This all did add up to some finger pointing... all had some ownership of the problem.

Thx Dave-in-Denver