Ok so i just bought a 1990 jeep cherokee and im having some issues with the trans, when put into drive it gets moving just fine but then wont shift into the next gear and just revs out, also it is real hesitant to go into reverse at times. i bought it knowing it had transmission problems and i've researched a bunch on it and i think i have a bad TCU so i unplugged like everyone is saying to do and it shifts fine manually. i bought a new/used TCU, plugged it in and no difference it still revs out until i unplug it again. could i just have bad pump pressure from the filter being clogged or something? really need help!!

 

Well, since you haven't had any replies yet, and almost diappeared from the last pagem I thought to bump your issue
You said you knew it had trans issues...do you know what has been done with that by the PO? That would be helpfull.
So, it shifts fine manually: that makes mechanical issues less likely.
What is the level and quality of the fluid?
Check the fuse in the TCU
The TPS is also involved in transmission shifting...

And since your thread is now bumped, others might chime in with more ideas..

 

The TCU fuse:

 

the PO told me he parked it once it started having troubles because it was just going to be a toy. ive ran probably 4 tanks thru it each of about the same quality and the jeep runs fine its self and the tcu fuse is all good along with the tps i did the voltage check on it and everything and as far as i know its good. the thing that doesnt make sense to me is i can be driving along at 55mph with the tcu fuse out shifting manually and once i put that fuse back in it just takes it right out of gear and revs out.

 

Sorry, discovered my typo. Not fuel, fluid....as in ATF...

 

Click on my link below and go to post 10.

 

Actually, do that and go to post 1. TCU grounds at the engine dipstick tube stud.

 

that sounds like it might be my issue cruiser54, because my cruise control also doesnt work along with some of the other electrical components in my jeep. im going to give this a try and i will let u know what happens. thank you

 

While you're at it, do post 3 also.

 

And if you have time....

 

Oh, and one more thing..........

 

haha... just do them all....so at least you can say "Yes, I did a search and yes I did ALL of the Cruiser54 Renix Tips"....

 

Almost have a brand new Jeep after doing them all!

 

also in your tips you talk about a upgraded headlight harness (#19) and i was wondering where you got it?

 

haha that makes more sense. the level is at the line and the quality is kinda unknown, it doesnt smell to bad and it still has alright consistency but i plan on changing it as soon as it gets a little warmer here