Well, I've never heard THAT before (roasted transmission content)

So, I took my Jeep

out on the trails for the first time Saturday. I didn't plan on going gonzo, some mild wheeling, maybe some light rock crawling 

The pic doesn't do it justice, that is steeper than it looks. Anyway, i ended up getting WAY more serious than I planned. The trans was slipping so bad I had to let it cool down every 100 yards or so. I nursed it to the parking lot, decided against a fluid change in an autozone parking lot, and babied it home 30 miles on the e-way. When I got home, I shut the engine off and heard this

Link

sounds like transmission fluid boiling to me. Shopping for a rebuild kit, convertor, and HUGE cooler....

Well done.  I would drop the pan look for clutch and other bad things.if not too bad,  I would flush and put a bigger cooler on it. I had a 93 cherokee that was super heated and the transmission fluid was black . After cooling down , changed fluids went on my merry way. the car had 300k on it when it left my flock.

Tcase has fluid in it too I think, might want to flush that as well

DrBoost said:

 

The pic doesn't do it justice, that is steeper than it looks.

I remember that hill and that park. Of course I had a proper Man You Well transmission....

logdog said:

DrBoost said:

 

The pic doesn't do it justice, that is steeper than it looks.

 

I remember that hill and that park. Of course I had a proper Man You Well transmission....

That was a fun little rock pile. 

Wait a minute...  These pictures look familiar...  You're in one of the 5.9 ZJ groups on Facebook, right?  I always thought I was the only 5.9 owner on here.  

As far as the trans, good call on adding cooling when you rebuild it.  I'd recommend adding a temp gauge too.  I'm running the second largest of the Tru-cool Max coolers on mine (takes up almost the entire upper grille) with the in-radiator cooler bypassed.  I've never gotten it above 180 or so since I put that cooler in (anything over 200 and it's time to start worrying, 220 and it's time to stop now and let it cool).  

As long as you keep the trans cool and give it an occasional fluid change and band adjustment, the rebuild should last.  I'm at 247k on my trans (never rebuilt) and the only issue has been a fried converter lockup clutch around 200k miles.  It's had a shift kit since 120k and at some point I cranked the line pressure screw up a few turns.  Still shifts great with no issues and shows no signs of wanting to give up.  

Yeah, I'm on two 5.9 groups on FB. The classifieds group, and the owners group. Cool that you're here too!  

I don't think I got water in it. I think I just pushed a tired okd trans (258,000 miles) too hard. I'm going to do a big ol cooler and I think I'm going to ditch the VIC and put the trans temp there. 

In a different Jeep, many moons ago, I installed a temp sensor in the pan, and installed a toggle switch to let me use the engine temp gauge on the dash. Similar operating temps for trans and engine, just flip the switch to toggle between the two. 

Now though, I'm sure I'd screw something up with the BCM or ECU. 

Yeah, the dash gauge is fed from the ECU, so there's no easy way to use that.  

while you're at it...

Jeep (dodge) uses a funny one-way check valve at the radiator in the cooler hose (bottom fitting I think).  They get gunked up and clogged all the time.  Do yourself a huge favor and remove it.  It's not high pressure (20 psi tops), so cut the end of the hose off to ditch that valve and clamp it back on.

I rebuilt a LOT of A518s and 45/46/47RE transmissions because of that valve.

I will second the advice for additional cooling, especially for off roading.

Three schools of thought:
1- bypass the radiator cooling circuit to an external cooler
2- add an external cooler and go radiator first, then external
3- add an external cooler and go external first, then radiator

I nearly always do #3 except in rare cases.  I do #3 because transmissions and their fluid are designed to operate at "warm" temperatures.  Too cool is not good.  But often times the radiator circuit can't handle the BTUs and it lets things get too hot.  External first takes the bulk of the heat and gets rid of it before the radiator, then the radiator sheds the rest of the heat sending 190 degree fluid back to the transmission.  This also helps cold start up.  The radiator circuit is also designed to help the transmission get UP to temperature where it can operate properly.  When fluids are too cold, they don't flow as quickly, which means shifts can take longer... which means more slippage and wear.  Doing it this way means you are ensuring that enough heat gets dissipated, and also ensuring that proper heat is maintained.

Doing #2 dumps the most heat into the water adding stress to the the engine cooling, then over-cools the fluid before sending it back.  It also greatly adds to the time it takes for the transmission to warm up.

Doing #1 is a crap shoot.  You'll either overcool or undercool the fluid.

I run a 160* thermostat in the lines to avoid overcooling.  Plus, the cold side of the rad doesn't really keep the trans fluid very wam when you need it to (in really cold weather on the highway).  

For the check valve, it's possible to unscrew it from the lines, punch the guts out of it and put it back together as just a fitting.  That's what I did on mine.  

Thanks folks. I appreciate the real-world feedback. 

Has anybody seen a trans get hot enough to boil the fluid like in the video??

My old s10 did. I was in stop and go traffic thru a town after a long highway drive. Couldn't figure out what the sound was until it started blowing out the vent. Fluid and filter change managed to fix it but I never trusted that 4l60e again.

Hmm. I upgraded to a larger external cooler on mine, about half the area of the AC condenser. I still haven't done a gauge yet, but it's in the plans. Sounds like I also need to hunt down this mysterious check valve too.

Mine's a 5.2 and only 166k, and no issues *yet.*  But I'd sure prefer to keep it that way.  I've got no intentions of going rock crawling, but things happen when you're out in the wilds. I had no intention of going full-on mudding this weekend either, but sometimes that's the only way home.

Doc, does your niner have a factory trans cooler? I was told there was one year they made the niner with no trans cooler, even if you got the tow package. Not sure how accurate that is...

In reply to ultraclyde :

All V8 ZJs from 93 - 97 had the factory aux cooler and any 4.0 with tow package had it.  In 98, they must have run out at the factory or something.  All 98 ZJs have just the in-radiator cooler (no aux cooler) regardless of engine or tow package.