Trans won't shift until I hit 25mph

In the mornings after the jeep has been sitting overnight, the trans won't shift until I hit about 25mph and then let off the gas completely. There is no change if I manually cycle the gear shift.

The trans will shift normally after a mile or two of this behavior. If I go somewhere and let it sit, this does not happen. It seems to only happen after a prolonged period of rest (overnight).

The only other abnormal behavior I can make out is that at high RPM, it seems like the trans delays in shifting. Otherwise, there's no issues under normal driving.

The fluid is red and full.

91 XJ, AW4, 4.0L

Check your TPS. It caused the same issue with my MJ.

Alright, I'll do that. Probably just replace it and keep the old as a spare.

A bad or out of spec TPS can have you chasing and swapping TCUs for days.

Bent said:

A bad or out of spec TPS can have you chasing and swapping TCUs for days. :blush:

Click to expand...

Good to know!

Check TPS, adjust TV cable too. TPS going out causes weird shift issues. Pedal travel all the way to floor? If no adjust TV.
Have you unplugged the TCU and driven manually shifting?

Okay, swapped in a new TPS and no change.
I already adjusted the TV cable at the throttle body: no change.
I have not unplugged TCU and manually shifted, but I can do that probably tomorrow morning.

Okay, had a chance to drive with the TCU unplugged and it shifted just fine; there were no issues.

So this narrows it down to a TCU / wiring issue?