Ok so I finally got my new jeep moving under its own power after swapping the old motor trans and t-case from my other cherokee into it. Come to find out the trans won't shift while driving down the road. Everything worked fine before I pulled it and now nothing. Anyone have any ideas of what could be wrong? It seems like it shifts from first to second because when I downshift it from drive and go from 3 to the 1-2 on the shift indicator it slows down and revs up. Any and all help appreciated. It's an '01 Cherokee by the way

 

What parts did you swap, which did you keep and what year was the donor?

 

I swapped the entire drive train and wiring harness. And they are both 2001 Cherokees. The only difference between my old jeep and the one I swapped everything into is mine had factory tinted windows and cruise control and this one doesn't.

 

Does '01 still have a stand-alone TCU? If so did you swap that too?

 

Did you swap the transmission control harness as well?

In 1998 the transmission design was changed to include an Input Speed sensor, and the Output Speed sensor was changed as well. The TCM will be looking for inputs from both of these sensors.

Not sure if a 1991 ECM will understand what's going on with a 2001 TCM and Speed sensors installed. Of course, you can't put a 2001 PCM in your 1991.

Edit: Ooops, didn't read where both XJ's were 2001. Disregard above.

 

I swapped everything from my old 2001 into the 2001 I have now. The '91 I mention in my signature is my old jeep. I did not keep my old trans control unit from under the dash. I just plugged my harness into that one. Didn't think of taking the one from my old jeep at the time.

 

Couple of Q's:

Did you swap over the Torque Converter?

Have you tried adjusting the TV Cable?

Is the fluid full?

Have you tried the manual shifting test? Like this:

AW4 MANUAL SHIFTING TEST (FSM Procedures)

(1) This test determines if problem is related to mechanical or electrical component.

(2) Stop engine and disconnect transmission control module.

(3) Road test vehicle. Shift transmission into each gear range. Transmission should operate as follows:

• lock in Park
• back up in Reverse
• not move in Neutral
• provide first gear only with shift lever in 1–2 position
• operate in third gear only with shift lever in 3 position
• operate in overdrive fourth gear in D position

(4) If transmission operates as described, proceed to next step. However, if forward gear ranges were difficult to distinguish (all feel the same), or vehicle would not back up, refer to diagnosis charts. Do not perform stall or time lag tests.

CAUTION: Do not over speed the engine during the next test step. Ease off the throttle and allow the vehicle to slow before downshifting.

(5) Continue road test. Manually downshift transmission from D to 3, and from 3 to 1– 2 position. Then manually upshift transmission through forward ranges again.

 

I swapped the motor, trans, and t-case all in one shot together. What's the TV cable? And yes the fluid is full and clean. I will try the manual shift test tomorrow if I have time. And the TCU is the box under the dash above the gas pedal right? Just want to make sure.

 

TV Cable is the cable going from your throttle, down to the transmission. Sometimes called the kickdown cable. Simple adjustment procedure, but I personally don't have the info on it. Someone else will, though

 

Yes, the TCM is where you stated.

 

Yeah when I snapped the unibody rails on my old XJ, which is the reason for swapping everything into another XJ, everything worked fine.

 

Well it turns out that the trans will shift manually when the TCU is unplugged. Guessing that means the TCU is no good.

 

I guess that was the intent of the test.

However, you may want to do some electrical checks before replacing the TCM.

Refer to the TCM connector pinout below.

Resistance Checks:

Disconnect battery negative post connector.

Use a quality digital Ohmmeter.

Remove the connector from the TCM.

Input and Output Speed Sensors:

Measure between pin cavities 1 and 2, and 3 and 4. Each should read around 625 Ohms. If you see an open or very high or very low resistance, the Speed Sensor or its wiring is defective.

Solenoids:

Using the negative probe of the Ohmmeter, touch pin cavity 24, then touch the pin cavities 11, 12, and 13. Each should read 11 to 15 Ohms. Any solenoid reading out of range could mean the solenoid or its wiring is defective.

Brake Lamp Switch:

Using the negative probe of the Ohmmeter, touch pin cavity 24, then touch the pin cavity 23 with the positive probe. With the brake pedal not being depressed you should read continuity (max 5 Ohms). Depress brake pedal, you should now read open.

Voltage Checks:

Reconnect battery.

Using the digital Voltmeter, set to 20 Volt DC Scale.

TPS Input:

Turn key to RUN.

Using the negative probe of the Voltmeter, touch pin cavity 16, then touch pin cavity 17 with the positive probe. You should see the TPS idle voltage. Depress gas pedal to full throttle, you should now see TPS WOT voltage.

Transmission Range Sensor (NSS):

Key still to RUN.

Using the negative probe of the Voltmeter, touch pin cavity 24, then touch pin cavities:

9 with the positive probe while the trans selector is in the "3" position (TRS 3 Sense).

21 with the positive probe while the trans selector is in the "1-2" position (TRS T42 Sense).

22 with the positive probe while the trans selector is in the "D" position (TRS T1 Sense).

You should see battery voltage at each of these selections.

Fused Voltage inputs:

Key still to RUN.

Using the negative probe of the Voltmeter, touch pin cavity 24, then touch pin cavities 25 and 26. You should see battery voltage.

 

Well I went to my local junkyard and spent 30 bucks on a used TCM and my trans shifts fine now.

 

....Or you could test it that way.

Glad you got it working!