AW4-need help with diagnostics!

i origionally bought 90 auto xj & it had a switch tapped into the wiring in my tcu (90 had External 10 amp Fuse) this made it shift like a manual-dog shift 1-3-D) sooo
i bought a 95 tranny with way less miles out of a stocker and swapped transmissions.
NOW
when i shift its way smoother and nicer, so i stuck a new fuse in the tcu and its stuck in 2nd gear and wont shift i got it up to 4500rpm and figured it wasnt going to nice if shifted after that so i didnt push it.
the tranny was low on oil so it idled in neutral for 15 min while i added oil to it, its where it needs to be now.
at this point i think theres something wrong with the tcu because it was tapped into but what does this sound like? tranny problems or electrical problems? all electrical cables from tranny matched up and the kick down cable was identical. im stumped please help!

If you disconnect the TCU, and shift it manually, at all the normal rpm/shiftpoints and the tranny shifts as told to...I would guess that it is an electrical problem...

when the TCU detects trouble it will go into a limp mode and stay in 2nd so you can get it home/to the stealership etc. since you say it shifted fine with the TCU disconnected it is definitely not mechanical, so it is either going to be wiring/sensors or the TCU itself. I had mine go into limp mode a couple of times when my TPS went bad and all I had to do is shut off the jeep and restart it to reset the TCU (mines a 97 tho so I don't know if its the same). that said I would try testing/adjusting or replacing your TPS if necessary. also being a new trans and all you could try pulling the neg battery cable overnight to reset the computer and TCU. after that I really don't know where to point you next other than trying a known working TCU, and I'm sure theres probably a way to test the sensors, but I don't know how :dunno:

I don't believe the 90 TCU has a limp-home mode. Is the NSS correctly adjusted? You could try unplugging it altogether which'll make the TCU think you've got the shifter in (D). Rear speed sensor hooked up? I assume the old tranny shifted okay with the TCU receiving power?

no the old tranny didnt shift on its own very well(sometimes to soon usually way to late) thats why the guy put the sloppy switch on..wich cooked the tranny cuz it always ran hot from manually shiftn it. so i swapped trying to eliminate the mechanical side of it wich confirmed the electrical mishap. i disassembled/cleaned put dialectric grease in the nss switch upon installation & havent touched it since, speed cable is instaled at this point is there any adjustments i can do? i was going to look at the wiring to & from the tcu, this sucks because there are so many things that can effect shifting. after i get a few hundred miles on it im going to drop the tranny pan and check the solenoids but at this point im doubtn its the transmission,

please keep the thoughts coming

since it was shifting late/early before I'd put my money on the TPS, the RENIX gurus will be able to help you more, but there are two adjustments on the TPS, one for the ECU and one for the TCU signal (might as well adjust both while you're in there IMO) could also be a bad TPS or bad wiring/ground/connectors/etc.

Only one adjustment - loosen the screws and rotate the whole sensor to get the correct voltage at closed throttle. A bad TPS would have been my first guess too. You can check the solenoids by measuring the resistance at the TCU connector, which will also verify the wiring to/from the TCU. Running with the TCU powered off doesn't let the t/c lockup which will generate extra heat.

When you swapped in the 95 tranny, you didn't swap the TCU did you? You need to stay with the 90 TCU.

no i didnt swap the tcu's i havent had much time to work on it lately so sorry about not having any more info. next ill do the tests you've told me about and see what i get, i do have the jeep service manual and electrical but its for the 89 and i have the 90. it shouldnt really be much different tho right?
thank you for the help

The service manual should be the same, although you might find a few changes in wire color.