Jeep shifting problem (ITS BAD)

C

cherokeeproject

NAXJA Forum User
Location
Cypress, TX
so some time ago i started having problems shifting in my jeep. i had just bought a new car so i didnt bother with it and let it sit for about a year with the occasional use to move my roommates boat in and out of the backyard (expensive tractor). now ive brought it back out in hopes to use it for hunting season, if i can get it fixed. heres where yall come in.

so its a 96 cherokee sport 4x4 w/ AW4 tranny. 225K miles.
the problem is that when i get hard on the throttle (~ 60% full throttle) the engine rev's to red line and holds there until i let off the throttle (to ~20%). then the engine will shift hard into the next gear. However, if i baby it and drive it as if im an old lady, it shifts normally.

i have researched on other forums and had tried several things. i first adjusted the throttle cable but im not sure i did it right but it still acted as before. i then tried to unplug the throttle positioning sensor and when i unplug it the engine died. so i replaced the TPS and with a new sensor the problem wasnt as severe but still bad. i then tried unplugging the TPS and shifting manually. the engine ran with the new sensor installed and unpluged, but when attempting to shift manually the transmission stayed in first gear.

so now im looking to yall for some help any suggestions for what to try next?

thanks in advance!
 
You have to unplug the TCU (transmission control unit), not tps (throttle position sensor) to shift the tranny manually. If it shifts fine its electrical, if it still shifts bad it is internal.
 
so ive done alot today. i checked the pins on the TCU as instructed by lawsoncl. the results came back as follows...

all pins were meeting specs except pin C9, C14-C16 (which controls the solenoids), and stragely there was no wire existant for pin D1, which according to the link is supposed to be the voltage supply for the throttle positioning sensor. did something change on the 96 that this post was not aware about?

also i unpluged the TCU and test drove it shifting manually, it shifted just fine and acted as normal.

i tried calling O'rileys and Autozone to see if they had a replacement TCU and neither even had records for one. would local shops even carry something like that, or would i have to order online?
 
You're kidding me. NEVER buy a new TCU for that kind of price!

The one from the 92 is exactly the same as the one in the 96. It should be part number 5602 6769.
 
cherokeeproject said:
so ive done alot today. i checked the pins on the TCU as instructed by lawsoncl. the results came back as follows...

all pins were meeting specs except pin C9, C14-C16 (which controls the solenoids), and stragely there was no wire existant for pin D1, which according to the link is supposed to be the voltage supply for the throttle positioning sensor. did something change on the 96 that this post was not aware about?

also i unpluged the TCU and test drove it shifting manually, it shifted just fine and acted as normal.

i tried calling O'rileys and Autozone to see if they had a replacement TCU and neither even had records for one. would local shops even carry something like that, or would i have to order online?
Click to expand...

No voltage on D1 is normal. In the older Renix setup, the TCU powered its side of the dual-output TPS. In later models, its a single output and gets its power elsewhere. The D9 is likely a dirty NSS sensor which can be cleaned http://www.boyandjeep.com/tech-articles/aw4-neutral-start-switch-rebuild.

What were your resistance measurements on C14-16? Even though you replaced the TPS, it still sounds like a TPS problem to me. The ground wire to it still good?

For interchange, I think you're stuck with 96. OBDII started in 96 and I think it was 97 was when the connector changed. Ebay is a good place to find them used if a local yard doesn't have one.
 
I was afraid of the OBD II change in 96 for this one too, but when I checked the catalogs, 91 has its own TCU (probably due to the power/comfort switch and nothing else), 92-96 with the AW4 all use the same TCU as each other. 97 has its own TCU, 98-01 are another. I am not certain of the 87-90 TCU interchangeability.

Another note for anyone finding this via a search... 4cyls throw this completely out the window, this info applies only to 4.0L/AW4 drivetrains.
 
I'm curious why 91 is different as well. Probably due to the power/comfort option which I think you could just hard wire if you needed. I thought the the 21 to 23 spline count and 4th gear output ration changed between 90/91. It has the green connector and looks like it should plug into 92-95 (or 96 as your catalog indicates). I wonder about the 93 ZJ interchangeability too. It's TCU had the green connector as well.

97 is the bastard year when the connector changed, but the sensors had not changed yet. 87-90 have the grey connectos and I'm pretty sure they are interchangeable.
 
lawsoncl said:
No voltage on D1 is normal. In the older Renix setup, the TCU powered its side of the dual-output TPS. In later models, its a single output and gets its power elsewhere. The D9 is likely a dirty NSS sensor which can be cleaned http://www.boyandjeep.com/tech-articles/aw4-neutral-start-switch-rebuild.

What were your resistance measurements on C14-16? Even though you replaced the TPS, it still sounds like a TPS problem to me. The ground wire to it still good?

For interchange, I think you're stuck with 96. OBDII started in 96 and I think it was 97 was when the connector changed. Ebay is a good place to find them used if a local yard doesn't have one.
Click to expand...

well it wasnt just no voltage, there was no wire to that terminal. not even evidence of one ever existing.

i cant remember the resistance measurements but im can double check sometime soon.

im going to check a scrap yard that i know has a cherokee that might still have a TCU.

Would it be a wise decesions to buy a used TCU? or are they something that should last "foreever" ?
 
i'll be checking the ground wires on the TPS tom just to make sure. But, im thinking im going to check the solenoids before i buy a new TCU. they seem like they might be the problem.
 
cherokeeproject said:
i'll be checking the ground wires on the TPS tom just to make sure. But, im thinking im going to check the solenoids before i buy a new TCU. they seem like they might be the problem.
Click to expand...

ok so i finally got around to doing some more work on the jeep. did alot and got no where. i checked the ground on the TPS and no problems there. drained all the tranny fluid dropped the pan and checked each solenoid, each one was within spec of 11-15 ohms (each one was around 12-13 ohms). the only thing i havent done yet is replace the tcu. and i headed to the junkyard to pick one up only to find they closed at 6:00 (it was 6:12) Sucks A$$..... any other suggestions? i honestly dont think its the TCU since the numbers i got were within spec except for the solenoids which i just checked. is there something that could be in the wiring between the TCU and the solenoids themselves??
 
so ive been reading through the AW-4 manual and it suggests that the valve body could be faulty. anyone agree? im not too familiar with the transmission and all its parts and workings but if someone else out there knows something that could help it would be greatly appreciated.

so even with the TCU unpluged and performing a manual shift test it acted normally. meaning the problem is electrical right? wouldnt that eliminate the posibility that it could be the valve body?

If it does turn out to be the valve body, i do have a spare AW-4 off of a 87 2wd. would the valve bodies be exactly the same on both models?
 
cherokeeproject said:
so ive been reading through the AW-4 manual and it suggests that the valve body could be faulty. anyone agree? im not too familiar with the transmission and all its parts and workings but if someone else out there knows something that could help it would be greatly appreciated.

so even with the TCU unpluged and performing a manual shift test it acted normally. meaning the problem is electrical right? wouldnt that eliminate the posibility that it could be the valve body?

If it does turn out to be the valve body, i do have a spare AW-4 off of a 87 2wd. would the valve bodies be exactly the same on both models?
Click to expand...

I'm still leaning towards an electrical problem since it shifts okay manually. It is still possible that its a valve body problem but that really doesn't seem to fit your symptoms.

You said you measuring the solenoids at the pan measured good. Did they measure good checking at the TCU connector as well? That would rule out a problem with the wiring to the solenoid.

When checking for a used Trans Computer, it should have a green connector. Red would be from a Grand Cherokee and the Chrysler tranny, and grey would be from an older Renix setup.

Anyone live near this guy that can loan him a working trans computer?
 
lawsoncl said:
I'm still leaning towards an electrical problem since it shifts okay manually. It is still possible that its a valve body problem but that really doesn't seem to fit your symptoms.

You said you measuring the solenoids at the pan measured good. Did they measure good checking at the TCU connector as well? That would rule out a problem with the wiring to the solenoid.

When checking for a used Trans Computer, it should have a green connector. Red would be from a Grand Cherokee and the Chrysler tranny, and grey would be from an older Renix setup.

Anyone live near this guy that can loan him a working trans computer?
Click to expand...

when i measured the solenoids at the TCU i got no reading. (or basically 0 ohms) but im starting to think back on it and wondering if i had it set to read out of the meters limits. :-/?

i also read in the manual that the transmission could send an error code that could be read by a DBII tester. is this what your referring to as a trans computer?
 
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