TC locks up early

[Sonex522]

2000 XJ, 73k miles, 4.0 auto. When I read the list of problems people have with their Jeeps I wonder what I've gotten myself into Waiting for the head to crack. No wonder Fiat bought 'em. Birds of a feather....

My trans shifts into 4th at 45 mph, and it seems like the torque converter locks at the same time as it shifts, making it bog down to 1500 rpm. If I leave it in 3L up to 55, and then shift it into D, it seems a whole lot more normal. If I accelerate less like a granny i.e. 1/2 throttle, it's a bit better, but still not what I'd like.

I tried the cable adjustment trick and played around with different amounts of slack. That just changed how firm the upshifts are.

I did a drop and fill of the trans fluid a couple months ago. There's a big yellow sticker under the hood that says AW+4 fluid. That doesn't jive with the owner's manual, but I used it anyway seeing as the owner's manual can't even get the fuses right.

 

[lawsoncl]

The shift points are controlled by the Trans Computer (TCU). The two main inputs are the throttle position from the TPS sensor, and the engine rpm. The TPS sensor is mechanical, very similar to a vilume knob and they do eventually wear out and get scratchy. My bet is that you have a bad TPS sensor, which is a very common problem.

No such thing as AW+4 fluid. Using ATF+4 in the AW4 tranny has been the subject of considerable debate in these forums. The consensus has been to stick with Dexron-III as that's what the manufacturer designed the tranny for and Chrysler spec'd up until recently. Rumor has it they changed the spec once the trannies were all out of warranty to reduce the number of oils the dealer has to stock. Those reporting problems running ATF4+ have talked about excessive slippage and running hotter due to the slipperier ATF+4.

 

[ROBZ95Xj]

every xj ive owned the tc locks up at 45, i see no problem with it

 

[techno1154]

Under normal or light excellaration, the AW4 lock up in 4OD at about 45 MPH +/- . A little less going down hill and a little or a lot more going up hill or under hard excellaration. Do some hard(er) take off's and see if the shift points change.

 

[Sonex522]

Thanks for the info guys - you rock.

AW+4. Duh. I meant ATF+4.

If 45 mph for lock up is normal, I guess I won't obsess about it too much, but it seems to lug the engine. I hit 45 right at the base of a hill every morning on the way to work, so I'll just manually shift it I s'pose.

I'll test the TPS, too. It'll be a good learning experience.