First, current build (relevant basics):
2011 JKU Sport Auto
UD44 front, 5.13 gears, 37s, viper throttle body, screaming demon coil pack, 10mm wires, Mishimoto trans cooler with new lines.

Last fall in Moab I got the hot oil message on the dash and immediately pulled to cool it. Next day creeped into town and had the trans flushed, filters changed, etc and order the cooler. I have since been monitoring temps regularly, and most of the time it stays cool except on long climbs, and for some reason it’s always worse in Moab. I can wheel all day, no problem, but if I have a headwind or a climb, or both, it will heat up quick. Also never happens in 4lo. I’m wondering if adding a supercharger would help, or make things worse. Would the additional torque put less stress on the tranny, or just cause more heat?
Note: I have no other cooling issues (except maybe intake temps on a trail). Also, please don’t say swap... a $5k supercharger is not comparable to a $20k swap, and I don’t have the means to do a janky swap, on my own, for $5k. Thanks

Tl;dr: will a supercharger help my trans run cooler?

 

I can’t think of how adding a supercharger will help your transmission. Your transmission will still have the same or more force applied to it and will still turn at the same rpm’s internally.

 

it’s the same rpms in 4lo as well, but it never gets above 150. I know the 3.8 is not properly geared, so wouldn’t the added torque put less strain on the trans? I don’t know why I can’t fully wrap my head around this.

 

I don’t think the transmission has the high load for a long period of time that you will have when driving in 2wd up a hill. I wish I could tell you why it’s overheating in the first place but I would think that before modifying anything you should make sure everything is healthy to begin with. If you add a supercharger to something then you’re opening a can of worms because now you may have to deal with troubleshooting multiple things at once if you run into issues with your supercharger.

On another note, I’ve never been a fan of a super for an off-road rig anyways. I want simplicity when I’m in the middle of nowhere. You add more intricacies and you’re asking for something else to break.

 

You mention cooling is the issue-have you looked at Ron's post about putting a mechanical fan on the 3.8? It seems that would keep things moving as you have constant air flow.

 

so Im guessing the original oil temp issue was the AT temperature and not the radiator? Does ur tranny cooler have a fan? how did you size the cooler? I only see you mention 150*F as when ur in 4lo....what temps are you seeing during other driving conditions? where is ur tranny cooler located? whats the ave temp in Moab..vs where you daily drive? 175*-200*F is the sweet spot for most AT's, dont know much about the jeep tranny, but spent time researching and dealing with a Tacoma AT.....what fluid are ya running?

 

I have not, I will look into that.

Correct, engine temps are consistently at 190. Tranny cooler does not have a separate fan, it is mounted in front of the radiator. I’m not sure of the exact dimensions, but it’s approximately 12”x12”x1.5”. Since installing the cooler, under normal driving conditions (no strong headwind, flat ground, etc) the trans temps hang around 100-120. Ambient temp has no significant effect, only load. The first time it overheated was on the highway, at speed, 3-4% grade, 10pm, and 55 degrees F. Last time it got over 220 (before I shut it down and let it cool) was last weekend climbing La Sal mountain pass it was about 40 degrees F outside 6” of snow on the sides of the road. I have also driven in 100+ weather in SoCal and the temps still hang around 100-120. Once the 3.8 trans gets above 220, it starts acting funny, so if I see it creeping up to 175, I’m on edge. I believe 230-240 is where the hot oil light comes on.
FYI: all other trans functions are good. It shifts smooth, doesn’t slip, doesn’t hang in gears, nothing that would make me think there is something wrong with it. This only happens under heavy load in 2hi and 4hi.

 

Just out of curiosity, when you had the transmission flushed when you first overheated it, did you check the fluid? What was the fluid like? Any particles in the fluid?

How many miles are on your transmission? If internals are worn (clutch packs, torque converter) then you may have slippage and can get overheating.

 

hm, very plausible. When I checked the fluid after it overheated it was grey and badly burnt. The tech that flushed it said the same, but also noted he did not see any foreign material or metal shavings. The main drivetrain has 145k on it, along with about 35k miles behind our motorhome.

 

suspect sv_dude may be right, burnt fluid is a bad sign. the other thing I wud do is research how the lock up is supposed to function, if urs isnt that is often a source of heat generation....