I have a 1998 XJ 4.0 auto trans and when I'm on the freeway in OD (I'm guessing on that part) and press on the gas the RPMs go up then drop back down. What could this be? Any help would be great.

 

If you take your foot off the gas then press it again it shifts out of OD.

 

I don't think it's shifting out of OD right away. When let off the gas then get on it again the RPMs shoot up then fall back down without letting of the gas.

 

The lockup torque converter temporarily unlocks when you press the gas, then when it locks again, the rpm's drop back down. If you press harder it will unlock the converter AND downshift out of OD.
I am amazed at how many rpms it actually drops when the converter locks. Seems like a bunch more than other vehicles I've driven.

 

I'm having an intermittent issue like this. The TC locks up when you give it around 20% throttle. like the lockup is delayed. Am I right?

 

TC controls 4wd.. You sure on your terminology? Is there a slight hesitation between when you push throttle and when you feel it engage torque to the driveline? If so it sound like a bad u joint... Unless I misunderstood..

 

sorry, I used TC as short for torque converter, forgot I was on a 4wd forum. No lag on power to drive line, the torque converter locks up when i pass 20% throttle, but not before. The closest thing to hesitation that I feel is when i put the peddle down and I'm going 45 or 50 mph, it locks prematurely (when i pass 20% throttle), lowering my rpm and taking me out of my power band.

 

That sounds about right. The rig is fine until I get around 45-50 mph. Then when i let off the gas and get back on it I expect it to have down shifted out of OD but it doesn't (unless I floor it)...and the RPMs rev up then drop with no real acceleration.

 

Sounds like You need to adjust the kick down cable. It's attached to the throttle body. Sounds like you need to tighten it down some to take up the slack.

 

I did use a OBD and it didn't throw any codes? How would one go about adjusting the kick down cable?

 

Adjusted to kick down cable. Still have the same issue. In OD I'll let off the gas and then when I get back on it the rpms will shoot up then drop down.