Check the connectors that run down to the trans by the oil dip stick. There are 3 large connectors that can cause problems if dirty or damaged. Check on some of cruiser54's tips. I believe he has a write up with some pics

 

I have a similar problem. Mine happens when I'm cruising at hwy speeds between 55 and 70. It will run at 2000 rpms and be fine then it will jump up to 2500 and cruise there. If I go up and incline it will bear down and be back at 2000 then when it levels off it jumps up again. It may not be a huge problem, but I bet it is eating my mpg like crazy...

 

that's the start!.. the demise of your tranny.. mine started the same way, then started slipping, then it would lock up in OD, then lock up in 3rd.. every now and again, all gears just went away while cruising at 55+.. then you just come almost to a stop, and you have 1st gear only.. stop, shut it off, wait a bit, start it and everything is back.. for a little bit.. "you never know what gear is going away next or what your trans is going to do"..

 

unplug your tcm and shift manually until you get it fixed

 

That is very comforting haha, well crap.

 

well in the mean time it won't be shifting up and down all crazy on the highway.

 

for sure man. I think I'm gonna look into replacing the TPS and see if that helps too. seems pretty straight forward.

 

its a pretty easy fix I replaced mine with a duralast brand not sure if I got a dud because I noticed no difference at all. I could put the old one back one and it drives the same.

 

can you have a bad tps and still read the right voltage because my 90 is doing similar things
and i checked the voltage in the tps like your suppose to on the renix motors and it was all good and i tried a new tcu and nothing changed

 

I wouldn't be the one to ask,but its probably not impossible.

 

NOW THAT makes a lot of sense? I'm trying to fix it, get ideas on what to look for, and you come up with this?

 

Hey guys, I am not sure I updated my post or not here. Prior post I made about my Jeep suddenly not able to shift past 1st gear lead to many tests to sniff out the root cause of the issue.

First we thought it was the servo's in the tranmission. I had them checked and replaced by my very good friend who works at a Jeep dealership. While he was at it he told me my transmission was clean as new with over 180,000 miles on it.

Next he brough over a TCU spare and replaced the one I had from under the passengers side dash. After a few starts and stops the next day I had him come back over to put my TCU back in.

Next he thought it was the TPS because this ties into the circuit, the 1987 went through a bulk head allowing for intermittent signal drops. So he remove the connections and soldered them and used heat wrap. This didn't fix my shifting issue, but did fix my starting problem where my Jeep would rev up high too long on an initial start before it dropped down to an normal idle speed.

Anyhow, the root of my issue was a 100.00 speedo cable about 1 foot long that connects to my transmission and some electronics. Nothing to do with my speedometer. Once he put the new dealer bought part on my Jeep has been running strong again like new. I have 218,000 no issues.

I think my friend told me the transmission with select trac for 1987 was built by Toyota and will out last my Jeep.

Oh yeah, the fuse under the passenger side under the dash to the TCU, great emergency trick like I see someone mentioned. Pull the fuse and you can manually shift out of 1st to 2nd and so forth. I was 80 miles from home, called my friend he told me about the fuse and my wife and I drove home like nothing happened.

Good luck gents!

 

so was it the speed sensor? That you replaced?

 

3 things:

Your TPS is probably bad.

Adjust your tV cable:

https://www.cherokeeforum.com/f2/free-quick-fix-41821/

Click on post 10 in my link in my signature.

 

Post 10 in my signature............