Hmm, I guess there are two questions here:

1. What is the minimum temp a transmission will generate even at zero degrees outside?

2. What is the minimum acceptable oil temp for lubrication?

 

Well most trans fluid is just a lightweight 10 weight high detergent oil.So the question is when does this lightweight oil freeze?or start to crystalize? Or get so cold that the pickup in the pan can not circulate it? My guess is very very cold maybe -20,-30 *f...If its that cold out...you are going to have many more problems than your trans fluid,believe me.

 

you have no idea how good of a question that is "My Friend". Make no mistake if I were to do it all over again, I would have bypassed the trans cooler years ago. Mine sprung a leak the other night 1 hour from home mixed real well with the cooling system and more importantly through out my pristine transmission. So over the last few days, I just ran/flushed about 28 quarts of the cheap Dex III ($2.50 quart) through the trans and Im still getting some slight coolant residue...not good

fricken messy nightmare, so to answer your question....you should have bypassed it yesterday...

or else you will your transmission (as I may have done)

 

My dads 99 ruptured internally and mixed ATF into the engine and colant into the tranny.
$1100 later, it was all fixed. ugh.

 

Damn...here I am thinking that Toyotas are uber reliable. I need to add this to my cooling system overhaul. Don't suppose there's a DIY around here somewhere?

<<<--- Goes off to use the handy 'search' feature...

EDIT: Just placed an order for the TRU-COOL 4454 at bulkpart.com - $60 shipped

 

How many of you guys have bypassed the rad cooler? I ordered the ipt cooler that has a bypass for cold temps so it should allow the fluid to heat up about the same as the rad cooler. The coolant in the rad will remain relatively cold until the thermostat opens which leads me to think that the ipt cooler with the bypass will be ok. I don't want the rad cooler to blow so I ordered the ipt cooler. A new factory rad is about 500 so the external cooler is the cheaper way to go. My issue is that I live in a cold climate and I know the factory runs the coolant through the rad for a reason. So you guys still think the best option is to run the ipt cooler only. Mt goat does the fan ever come on on your setup or did you put that on as extra overkill? For everyday driving I think the 4454 cooler may be fine. Thanks for you guys help.

Mike

 

Yeah the fan comes on in hot weather, not in the winter though.

 

Or you could not worry and just own a 5 speed

Seriously.. this is an excellent thread and should be put in the Wiki section.

 

Damn, does anyone know if the TRD cooler has a bypass? Ive had mine for 6 years now and no issue. Now im reading posts with higher milage trannys with some issues. I barely get to 100 degrees when its 32 degrees outside. During the summer it will get as high as 180 and these readings are comming out of the tranny. Am i over cooling it?

Out of the tranny into the radiator, out of the radiator into the TRD cooler, out of the TRD cooler back into the tranny....thats how i have it setup.

 

I've always heard that the TRD cooler was made by Hayden, Hayden coolers don't have a bypass.

 

Thanks....what IPT tranny cooler is the same size as the TRD?

 

The 4454 is very close (it measures 7 1/4x 11x 3/4 thick)

 

Has anyone any experience with the Davies Craig coolers? A friend of mine is in Oz and he said that he could buy one for me. I'm thinking of getting the 678 model. It's about the size of the TRD cooler but it does not have the black coating. I think it's uncoated. Is that ok?

I plan to have it installed beside the TRD cooler and have the rad cooler bypassed.

http://www.daviescraig.com.au/main/display.asp?pid=28

http://www.daviescraig.com.au/main/t...s.asp?prodid=6

Thanks!

 

mt goat have you run the 4454 cooler without a fan and if so did you see excessive temps? I want to run this cooler only without a fan. The climate here is not crazy hot and I only tow mild loads. Do you think that setup would be ok? I want to install it behind the grill so the cooling fan should pull air through the whole assembly.

 

I am thinking Toyota runs a transmission and motor cooler through the same exchanger for cost purposes. It is probably cheaper to drop in one unit than two. On paper, it might even appear to be more reliable than two units.

However, with multiple heating and cooling cycles, it appears cracks form within the coils leading to mixing.

I am thinking an inline t-stat with two loops would do the trick if you are running in extremely low temps.

 

Yeah I was running it in front of the radiator for a while just using the rad fan. That works too.

 

I have been running an external cooler for a while now,totally bypassing the radiator,just like a 97 landcruiser(modeled after family members routing).I have done the same on two other's 4runners(98,99)...

I mounted the cooler next to the a/c drier...behind the grill,running the hoses where the a/c lines run through the core support housing.....This works well,I did not mount a fan or a temp. sensor on mine or anyone's I have done...I watched the fluid condition for over a year and its still nice and red,no sighns of overheating...And I tow,and load down the cargo area with about 1000 lbs.

I would think you should mount a fan on it, if you mount the cooler out of the airstream of the front of the clutch fan..Or if you are using an electric radiator fan...

 

Using an electric rad fan shouldn't make any difference, that's what I'm running. The coolant cooling needs far exceed the cooling needs of the ATF, ie... if its hot enough for the ATF to need cooling the rad fan will be on too.

 

Toyota uses an internal tranny 'heat exchanger" style unit because it is far more efficient that air type tranny oil coolers. Liquid cooling liquid works better than air cooling liquid. This style also maintains a min temp because the radiator always keeps the tranny at a certain temp.

The best method to improve transmission cooling is to use the original tranny oil cooler as a pre-cooler for the external oil cooler. This way the radiator takes the temp of the fluid down to a temperature the air cooler can have more of an effect on. It also is still able to maintain a min temp by going through the radiator.

However this does not answer how to fix the issue of cracking transmission coolers.

 

While it is true that an oil to water cooler is more efficiant.I am not sure its always the best.90% of manufactures do this because it is cheap to manufacture,and it does keep the trans fluid at close to radiator temps.But on bigger vehicals,It is not the case...

Older landcruisers just use an external cooler,heavy duty diesel trucks,box trucks,ect just use an external cooler no radiator cooler at all,And these vehicals are made for towing/hauling and extra stress put on trans...I think its because under normal use the cooler in the radiator is fine,when towing/hauling it is recommended to supplement the cooler with an external one.Most manufactures would also agree with this.TRD does for toyota.

All I am saying is that there is a problem with our radiator coolers in 4runners,And transmission damage can happen quickly if not caught..I suspect the metal pipe cooler in the radiator is a type of alloy that over time rapidly reacts with the Ph lvls,and corrodes..If you put a big plate and fin cooler rated over GVW of the truck and place it in the airstream.There will be no problems in cooling the trans fluid...Thats my opinion,But I am recommending it to all the 3rd body style 4runner owners I know.