Trans coolers

'96 XJ 4.0 here and I'm starting to do enough towing that I'm considering putting in a trans cooler, although I'm not sure if I exactly need to. When I replaced my radiator this summer it had in and out trans fluid lines so I'm wondering if my setup already includes enough cooling that I don't need to add anything.

I originally thought I had a towing package (which I'm assuming would include additional trans cooling) but upon writing Chrysler with my VIN and getting a list of vehicle stats like this...

*J5 Cloth/Vinyl High-Back Bucket Seats
ADA Light Group
AHGP Spring Special Group
APAS Monotone Paint
ARWP Sport Decor Group
AWH Power Equipment Group
BAUS 117 Amp Alternator
BCDS 500 Amp Maintenance Free Battery
BGAS Power Front Disc/Rear Drum Brakes
CADP High Back Bucket Seats
CDBP Reclining Front Seats

... I didn't see anything like a towing package listed.

Whadda yall think? Do I already have good trans cooling or is there room for additional cooling?

As cheap and easy as it just do it. I don't tow and I have a B&M cooler. There is no down side.

The connection to the radiator is to heat the Tranny fluid in winter, not cool it for towing. I burned up 6 transmissions / torque converter / seals towing in the 1970's, on one dodge charger, in less than 100,000 miles (new rig) before I new what a trailer towing cooler was

Just buy one and install it. You want the fluid to go through the radiator cooler first, then the extra air cooled cooler you are installing. Not sure which line is the pressure feed line, you need to dig that up in old posts here.

Lots of talk about adding coolers, but how many AW4's have failed in XJ's because of heat? These are the transmissions that tolerate total loss of fluid on the trail at least once. And the transmission where folks bought spares because they blew every transmission they ever had, and not only did they not need the spare, they couldn't sell their spare either, because nobody else had blown one either... I have towed double axle trailers on the interstate for thousands of miles, and the transmission never cared. It is hard on the unibody and suspension though, and brakes are marginal, so if lots of heavy towing, look for another vehicle... Just keep the fluid clean and IMHO you don't need to fuss with coolers. Clean, fresh fluid can take more heat than old fluid. I drain and refill my pan every 20,000 or so. $20 for a jug of ATF is cheaper than a tranny rebuild.

Yes the AW4 is very under stressed in the XJ but heat is the mortal enemy of transmissions. I run a cooler on any vehicle I tow with or operate off road (pretty much everything I have ever owned) and look on it as improving the lonjevity of my transmission. I had an early 700r4 that went 250k before needing rebuilding (most lasted 75k-100k before needing a rebuild) in a Blazer that I both towed with and off-roaded. I run the cooler on my XJ bypassing the radiator as keeping it cool is more important than warming it up here in south Louisiana. My temps stay in the 140's-160's when towing. (This was before my teardown of the Jeep and lift, I haven't driven it after the lift, larger tires and adding the winch and bumper)

While the AW4 may not fail, the Dex III will burn up and form varnish in no time at all when overheated, and or foam causing cavitation of the fluid....I live in the south where heat and traffic is rough on the ATF....

md21722 said:

Lots of talk about adding coolers, but how many AW4's have failed in XJ's because of heat? These are the transmissions that tolerate total loss of fluid on the trail at least once. And the transmission where folks bought spares because they blew every transmission they ever had, and not only did they not need the spare, they couldn't sell their spare either, because nobody else had blown one either... I have towed double axle trailers on the interstate for thousands of miles, and the transmission never cared. It is hard on the unibody and suspension though, and brakes are marginal, so if lots of heavy towing, look for another vehicle... Just keep the fluid clean and IMHO you don't need to fuss with coolers. Clean, fresh fluid can take more heat than old fluid. I drain and refill my pan every 20,000 or so. $20 for a jug of ATF is cheaper than a tranny rebuild.

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Why wouldn't you put a cooler in. It's cheap insurance, easy to do, not expensive and just might save you some money in the long run.

I don't run my fluid through the radiator, just tranny to cooler to tranny. As far as I'm concerned it just adds heat to the tranny. It rarely freezes here and only gets really cold (and not sub-zero) if I head up to Tahoe or above 6,000 feet in the dead of winter.

After a few miles of "winter" driving the fluid is already up to 100 or so, in the summer the cooler keeps things nice and cool (always under 150) even towing or loaded unless I'm going slow and steep, even then it only gets to around 180. My tranny temp gauge has never gone past 200.

Do it!!

Like I said in my first post, there is no down side.

Unless you're making chili excessive heat is a bad thing almost universally.

:flame:

Almost, I said almost.

Definitely use a stacked plate cooler.

Double post

mine was running super hot when offroading it and going into limp mode. added the cooler and 33's and its running just fine. i didnt even do anything fancy cooler wise. i also bypassed the rad because i live in south east texas and it doesnt ever get cold here.

i think it cost me 50 dollars. also gave me an excuse to change my trans fluid which i did twice just to get some clean stuff in there.

First a few words of explanation, I’ve been away for about a year, so having settled back in, I’ve started working backwards to see what I’ve missed.

This thread drew my attention as I could relate it to my own experience & problems.

I was surprised to learn that what I’ve always assumed was a trans. cooler function is actually the opposite (thank you, Ecomike) Just wished I’d known that before, I might well have taken the easy way out & bypassed it.

Now post is quite a revelation as some years ago, having replaced the rad. I didn’t realise that there was a slight ATF leak until one day I pulled up outside the house, went to back up - & nothing happened. Checking the level revealed the trans appeared to be empty as was confirmed by the amount of fluid it took to bring the level up to where it should be. Now for the moment of truth, got behind the wheel, slipped it into reverse, let off the brake & wonder of wonders, started to back up the street. Big sigh of relief, reminder to fix the leak asap - & never another moment’s trouble. Fast forward several years, & another XJ required a new rad. Job done, I’d got wise to the quick release fitting onto that little pigtail pipe at the bottom of the rad & this time dispensed with it altogether. Probably only 6,7 miles down the road there was obviously something wrong, turned round as soon as I could & tried to get home. However got to a point where it wouldn’t climb a very slight gradient – there was fluid all over the front of the Jeep - & the road! Had it recovered & once home went straight to the cause of the problem: that new piece of hose (all of 4” long) I’d used to connect to the rad had split from end-to-end. Anyway, this time the gods were not smiling on me, because refilling the trans had no effect whatsoever, so much for “These are the transmissions that tolerate total loss of fluid on the trail at least once” – sorry md21722, didn’t work for me! So, here at least, that’s scrap, as could get another, probably at least as good, for what I was quoted for a re-build – or swapping in the trans. from my old one. Too late I meet a mechanic (with a Grand) who says he can probably fix it – for a couple of beers, if I remove the pan!



Oh, & looking at dantheman's photo, all of mine have what, to me, looks like an oil cooler right there - so there's nowhere to fit a trans. cooler.

XJI6191 said:

Oh, & looking at dantheman's photo, all of mine have what, to me, looks like an oil cooler right there - so there's nowhere to fit a trans. cooler.

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There are three components up front in dantheman's photos. Radiator, A/C condenser, trans cooler. The smaller one is an aftermarket tube filter. Most people say that the stacked plate is by far better, I've had my tube/fin cooler on both my Jeeps for years with no ill effects. I also have the radiator loop bypassed. Really cold around here is 35 F. Mostly the average temps in my area are around 65-70 (which includes 100+ summers and ~40F winters.
If you have the setup like dantheman...AND you have trans fluid going through it (like hoses attached) you already have a cooler. If not, and youi do any towing in hot weather, get one.

Sorry if I didn't make myself clear but, on all 3 of my XJ's, in front of the A/C condenser is what I'm sure is an an oil cooler (although I've never traced the plumbing) but the pipes to/from the trans. connect to the radiator. So, if I wanted to fit a trans. cooler - where could I put it?

XJI6191 said:

Sorry if I didn't make myself clear but, on all 3 of my XJ's, in front of the A/C condenser is what I'm sure is an an oil cooler (although I've never traced the plumbing) but the pipes to/from the trans. connect to the radiator. So, if I wanted to fit a trans. cooler - where could I put it?

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That is not an oil cooler, it is a towing package Transmission fluid cooler. The fluid is routed first to the Radiator to heat in the winter, then through the front of what you called an oil cooler, to cool overheating Transmission fluid when towing up hill climbs in the summer, then it returns to the transmission. Check the routing, you will see the line from the radiator connector to the cooler.

Quick thread steal, has anyone tried dexron VI? It's supposed to tolerate more heat and way better wear properties. GM doesn't even carry Dex III anymore and all trans that go in their shop get the Dex VI, even if they call for Dex III. I use Dex VI in my 01 Tahoe that says to use Dex III and it shifts better than with Dex III.

cherokeefan_1 said:

Quick thread steal, has anyone tried dexron VI? It's supposed to tolerate more heat and way better wear properties. GM doesn't even carry Dex III anymore and all trans that go in their shop get the Dex VI, even if they call for Dex III. I use Dex VI in my 01 Tahoe that says to use Dex III and it shifts better than with Dex III.

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Some people have reported using the newest synthetic on their newer late model AW4-jeeps, like 97-01 IIRC, but there were many reports of problems using Dex VI or V. I tried synthetic engine oil in my 87 4.0 once and it even leaked out the head gasket :shiver: onto the side of the block, and drank a quart every 200 miles and pissed the stuff out every place it could. You could not pay me enough to risk using the newer Dex fluids or synthetic on my AW4s. Why risk it?

If it ain't broke don't fix it, LOL. I get my DEX III in 5 quart bottles for $12.97/bottle at Walmart.

Dexron VI is not a synthetic as far as I know unless it specifically says. It's just a thinner viscosity with better heat and wear properties. Dexron V is another oil altogether. Dexron VI is recommended by GM for all transmissions that require Dex III or Dex VI. GM is the one that developed Dex III I believe. The newer 4l60e use Dex VI but the earlier ones used Dex III but pretty much nothing inside them is different. It was just a thought.

As far as the synthetic motor oil I think you had problems before. I started using amsoil at 100k or so and had no issues and it doesn't burn a drop.