Hey guys, new to the forum and first post here. I recently bought an 89 4.0 4wd that pretty clean for the most part, i've been going through the issues it has and i'm stumped on this one.

The transmission under light to moderate throttle shift 100% up and down. When you hit wide open throttle it shifts to its highest gear and locks the torque converter. Its a smooth shift, but its premature.

ive ordered up a gasket, filter and solenoids as well as checked the fluid level and adjusted the throttle cable. Anything else i should be looking at?

overall im really happy with it for 1250$. Plus it came with all the parts to fix it up. Once i get it running good im going to lift it and tear it up off road 😅

 

It's probably not the solenoids if it's shifting normally otherwise. I would suspect the throttle position sensor (TPS) first. Test with a meter before replacing. The TPS is not well sealed and easily killed with a pressure washer, so I would doubly suspect that if the engine bay was nice and clean like the original owner cleaned it. The 89 with the automatic will have two connectors off the TPS. The square connector is the one that feeds the transmission computer that you want test. Also beware that the aftermarket quality is hit or miss.

 

I may or may not have soaked the entire engine bay in cleaner, gave it a scrub down and pressure washed it prior to driving the jeep😅. Thanks for the advice, i'll check it out

 

Here is a good link for the procedure for adjusting the TPS (only applicable to the older Renix Jeeps).
https://cruiser54.com/?p=54

You'll also want to go through all of Cruisers other awesome list of Renix tips.
https://cruiser54.com/?page_id=75