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!!!!1989 jeep Cherokee 4x4 TRANS not shifting!!!!

Landon18

NAXJA Forum User
Location
Many,La
Hey Guys, I’m new to the jeep world but been around them and worked on a few and here recently picked up a 1990 Jeep Wrangler with a CHEROKEE XJ ENGINE AND AUTO TRANS SWAP. The trans won’t shift out of 1st gear when in Drive, but if I pull the fuse, it will shift out manually, everything I’ve read points in the direction of the TCU, TPS, or grounds not all installed properly. Although I haven’t replaced the TCU, I did notice on the back of it, it had some writing like it came from a junkyard so that makes me thing somebody already tried that. I have checked the grounds, everything looked good, I know there is a lot of post on this same matter but I just want to get some feedback on where to maybe start now?
 
What year is the trans and trans computer? If it's out of a 1991 or earlier, then the TPS input to the trans computer runs backwards of normal. That is 5-volts down to zero volts as the throttle opens. On the Cherokee, the TPS was a dual output with the square connector going to the trans computer. Later years, the trans computer accepted the normal 0->5 volts. Test at the trans computer connector and see if you're getting what the trans computer expects.

Measure the resistance of the solenoids, in particular #2. First gear is solenoid 1 engaged, second has both, third has the #2 solenoid, and 4th has neither. The third solenoid is the t/c lockup. Check that you're seeing something on the rear output speed sensor. Pre-1998 is a switch that closes once per rev. 1998 and later it's a pickup like the CPS and generates 4 voltage pulses per rev.

https://atsgmembers.com/memarea/bulletins/bulletins/98/98-03.pdf has a table of what you should measure on each pin at the trans computer.

Some additional info on the AW4 https://www.naxja.org/forum/showthread.php?t=1053970
 
CRUISER'S MOSTLY RENIX TIPS
RENIX GROUND REFRESHING
OCTOBER 30, 2015 SALAD 70 COMMENTS


The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.

All the components listed below ground at the dipstick tube stud:

Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition Control Module, Fuel Injectors, ECU main ground (which other engine sensors ground through, including the Oxygen sensor, Knock Sensor, Cruise Control and Transmission Sync signal. All extremely important stuff.

The factory was aware of the issues with this ground point and addressed it by suggesting the following:

Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. If the whole stud turns, you can use a 7/32″ six point socket or wrench to hold it so the nut can be removed. Worst case, cut the wires and remove the stud and nut. Install new terminal eyelets on the wires when going back together. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Surfaces must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Apply a liberal coating of OxGard, which is available at Lowe’s and other stores. Reinstall all the wires to the stud and tighten thdipstick stude nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, apply OxGard, and reattach securely.

Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for its intended use and subject to corrosion and poor connections at each end.

Remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Apply OxGard. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4″ socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely with a liberal coating of OxGard.
2 STRONG suggestions regarding the ground system:

I prefer to add a #4 gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18″ long with a 3/8″ lug on each end works great and you can get one at any parts store already made up. NAPA has them as part number 781116.

A further improvement to the grounding system can be made using a #4 cable, about 10″ long with 3/8″ terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. NAPA part number 781115.

For those of us with Comanches, it’s very important to remove the driver’s side tail lamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Add a 10 gauge wire, with an eyelet on each end, from that grounding point to a bolt on the frame. Better yet, on both Cherokees and Comanches, complete Tip 29 for the best fuel pump grounding. Be sure to scrape all mounting points to bare metal and apply OxGard also.Fuel Pump Ground Comanche

If you want to UPGRADE YOUR GROUND AND BATTERY CABLES with custom made parts, contact Paul at www.jeepcables.com
 
The kit looks like a good investment. I am going to consider it.
Cruiser54. Your description sounds like a labor-intensive effort but at a lower cost than the kit.
 
Not knowing what was swapped and what might be mismatched, I start checking the signals at the trans computer connector. The early Cherokees had a dual output TPS, the 0->5 going to the engine computer and the 5->0 going to the trans computer. Did they keep the cherokee intake manifold and dual output sensor? If that's mismatched, the trans computer is going to think you've got it floored and upshift at a really high rpm.
 
The exact wiring harness, motor, trans all got installed from the Cherokee into the wrangler, it has the dual output tps sensor, I will check to see if the TCM has a ground, when they swapped the motor they might have left off a ground maybe, I just will have to sit down and work my way through all of them slowly and make sure it’s right
 
The TCM is probably grounded if it's commanding solenoid 1 to get 1st gear. But if the TPS is missing it's ground the trans computer will think you're wide-open throttle.
 
So I got a new UPDATE! I actually got in touch with the original owner who done the swap and he said that it shifter fine when he swapped it initially but it eventually stopped shifting, so he swapped the TCM out and it fixed it but it only lasted a short while and it was back to not shifting again... so this changes things for sure so where do I start now?!!?
 
Good point on checking the fuse that's wrapped up in the harness near the TCU, although that typically causes starting in 4th as the main symptom.

Interesting that replacing the TCM temporarily fixed it. Possibly damaged wiring causing a short that kills the solenoid driver in the TCM? I'd be tempted to supply power directly to the #2 solenoid and see if you get 2nd gear.

If you stick an ohmmeter across the rear speed sensor, and spin the output shaft, you should see it close once per revolution. Backprobing with it connected and the key-on, you'll see the voltage jump between 12 and 0 volts. Trans and xfer case both in neutral, the output shaft should freewheel enough to see this, or just trans in neutral and spin a rear tire by hand.

The usual suspects for not upshifting out of 1st are:
- Bad #2 solenoids causes failure to shift into 2nd or 3rd
- Damaged wiring to the solenoids
- Bad rear output speed sensor or wiring, and the TCM doesn't know you're moving
- Bad TPS telling the TCM it's floored
- Throttlebody cable adjusted way too loose
- Bad TCM is the least likely
 
Would it run okay with a bad TPS? And also the vacuum line assembly on the motor looks to be in poor shape so I’m going to replace the front and rear vacuum line assemblies, it seems the engine revs great but at idle it surges for some reason so could that be a TPS issue possibly? I’m at work for about a week longer but I’m just trying to get a game plan for when I get home and can put my hands on it
 
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