YJ auto tranny

1993yj

1993yj

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Location
Salt Lake
What is the best auto transmission to put into a YJ? I have a 93 with the 4.0L, NP 231, and the stock auto tranny. I have already had to rebuild this tranny twice, and it seems to be slipping again. I am wondering if there is a better auto tranny I could swap in that holds up better to four wheeling. My jeep never sees pavement.
 
Do you have any kind of tranny cooler? Heat kills autos & rock crawling makes tons of heat. I'd try a aftermarket, heavy duty tranny cooler before spending the $$ on the adapters for a diffrent make of transmission.

Plenty of people are running that same tranny without problems, like RockMonkey. He uses his in a comp rig & is abusive to that thing. Far as I know, he's had no tranny problems.
 
Just the stock lines running up to the radiator. I have thought about installing a temp gauge to check that situation out, just need to get around to it.
 
Either I'm really lucky, or you're doing something wrong. I've got a YJ auto tranny in my comp buggy, as Greg said. The thing has been awesome. Tons of people use them hard and they have an excellent reputation. In fact a lot of people use the lighter-duty version of the 999 (the 904) with good results. I've had zero problems with it, other than keeping fluid in it when upside down. I have abused the crap out of that thing and never had an issue. I've slammed it from forward to reverse under power more times than I can count. I bought a spare from here when I saw one for sale cheap, but I've never needed it. I do run an aftermarket cooler. Perhaps it hasn't been adjusted correctly after the rebuild?
 
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I would assume. I have never actually looked for it, but it seems to shift at the right RPMs. I am changing the fluid and filter again, trying that before I do anything drastic or expensive. There seemed to be just the normal amount of debris in the bottom of the pan. I think part of the problem is with the pick up. It usually will only slip when I am on a steep climb, such as Bump Dump.

I am also wondering if maybe the problems could be coming from my NP231 w/Currie slip yoke eliminator T-case? It feels more like a tranny problem, but I sometimes get a weird vibration from my rearend when starting off. It doesnt seem to be coming from my driveline, and I used to think that it was from my rear axle when I was running a D35, but I have since put in an 8.8, and I still get the same vibrations.
 
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Forgot to mention the fact that every once in a while when I stop and put my jeep in park, turn off the engine, and then get out, it will start to roll away. I have since gotten in the habit of always setting my parking brake.
 
If it will not stay in "Park" you may need to adjsut the shift cable. If the adjustment is ok, the parking pawl or sprag may be damaged.

As for the transmission slipping, do you have a deep pan and filter pickup installed. Maybe the pump is cavitating, when your on an incline. If that is when this happens.

Frank
 
RockPaws said:
If it will not stay in "Park" you may need to adjsut the shift cable. If the adjustment is ok, the parking pawl or sprag may be damaged.

As for the transmission slipping, do you have a deep pan and filter pickup installed. Maybe the pump is cavitating, when your on an incline. If that is when this happens.

Frank
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I'm running the stock pan on my buggy and have never had a problem on a steep incline. And I've been on some very steep ones. :D The only time I've ever felt it "slip" was after I've been on my side, and lost a lot of fluid. After adding fluid it has always worked flawlessly. Maybe try just adding some fluid. Go ahead and fill it a bit above full. ;)

As much as I'd love to blame your woes on your transfer case, I can't really see any way for your t-case to fail that would cause that combination of symptoms. Rockpaws is right though, all your symptoms could be caused by your shifter not being adjusted properly.
 
I still need to check my shifter, but it only rolls occassionally. And I ususally do try to keep it a bit above full so that the pickup can always get fluid. And no, it is not a deep pan, it barely clears my exhaust as it is.
 
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This may be a dumb question to some, but the one thing that I do not know is auto trannys. I can do most everything else, but I have stayed away from these so far. Guess its time to learn.

Anyhow, are the 32rh and the 999 the same thing?
 
1993yj said:
This may be a dumb question to some, but the one thing that I do not know is auto trannys. I can do most everything else, but I have stayed away from these so far. Guess its time to learn.

Anyhow, are the 32rh and the 999 the same thing?
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Basically. The 32RH internally is identical to a TF999. To rebuild it you buy a 999 rebuild kit. Everything is the same except the 32RH has a Crank Position Sensor mounted on the bellhousing to make the YJ's fuel injection work. It's a 999 with a CPS. You could bolt a 32rh onto a CJ that has a 999 and it would work great. You can bolt the 999 from the CJ into the YJ and it will work, but you have to find some other way to mount a CPS. There are some aftermarket optins for that but they aren't cheap.
 
Check your shifter adj. ASAP
sounds like kick down is ok.
stock pan is fine just run 1/2-1 quart over full. I have seen a lot of TF trannies loose pump suction on steep climbs and go neutral.
I ran one behind a 401 in a heavy rig for 5 or six years and it held up fine.
 
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