Transmission Problems!

Hello, I am having problems with the transmission in my 1988 4.0/AW4 shifting on its own. I have currently changed the oil and filter, checked all my solenoids, found out solenoid #1 was bad (replaced with one from a 98 AW4). I have checked the TPS and adjusted it to within spec (.83). My dad and I tried hooking up a Snap-On diagnostic tool to the Jeep but it fails to communicate with the transmission testing side of the diagnosis. The power/comfort switch is missing from my dash but the connector is still hanging. I have jumped the switch from a wiring diagram to both power and comfort with no change. The transmission is mechanically sound because I can manually shift from 1/2, 3 to D and it will shift great so I am sure that the guts are in good shape. The symptoms of the transmission are when you put it in drive, it feels like you are trying to start in the Overdrive(4th) gear? Engine RPM's must be spiked to 2k+ to get any movement out of the vehicle and if you stay on the gas until it gets up to speed, it never shifts which leads me to believe it begins in OD. I have been researching and using an AW4 manual and cannot seem to locate the problem so if anyone has had this problem or has heard of someone who encountered this and has any advice, it would be much appreciated!

Thanks,
Caleb

If you need any more information, just ask!

Have you checked for power and ground present at the TCU connector? It's behind the knee panel of the dash on the passenger side.

Yep, we hooked a test light up and we are getting power at the TCU. There is an fuse about 6 inches above the TCU that I am now sure if it is factory or not but that fuse is good also!

http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html

Should find your answer in the article.

Thanks Joe! I will try that in the morning to see what I can come up with!

Well I got out to the Jeep tonight and did some testing.. I read through that article and began checking stuff. My fuses are good, I am getting power to the TCU. None of that changed the way it ran so i opted for the pin-by-pin check of the TCU. My results were all good except for the following.

C3- 0 V Should be 5-8V
C9- .76 V Should be getting battery voltage
C10- .3 no brake Battery voltage without brake depressed, 0 V with depressed (is .3 off too bad?)
D2- 4.75 V off, WOT 1.2 V Should be Approx 4.5 closed throttle, approx .5 WOT
D3- .78 V Should be .1 V or less
C11- Power-0 comfort-blown fuse My power/comfort switch is missing so I used this wiring diagram (http://www.naxja.org/forum/showthread.php?t=1011600&highlight=switch) to try to jump them into the correct mode. I jump from the solid black (Ground?) to the tan for power and get 0V(should be battery voltage). Then jump from solid black(ground?) to black/yellow for comfort?(should go to 0V but blows fuse instead)

Any suggestions? I adjusted my old TPS yesterday to within spec (.83) I believe it was 4.71 closed throttle and 3.91 WOT.

Ok, recheck your TPS at the 4 wire connector. Disconnect it, turn key to ON, throttle plate closed, measure voltage a "D" ground and "A" positive. Note the voltage. That is your reference voltage.

Ok, reconnect the 4 wire connector. Back-probe the connector at "D" and "B", turn key ON, THROTTLE PLATE CLOSED, now you should have 83 percent of the reference voltage, if not, adjust the TPS until you do--if you can't achieve it, replace the TPS.

FORGET WOT.

Well I just went and read the voltage. Across D-A I got 4.62V. Across D-B I got 3.91. That leads to .846 percent.. Would that little difference have that much to do with the readings at the TCU. I didn't have time tonight but I can adjust it back to .83 if necesarry tomorrow?

Well, I guess it depends on "tolerance stacking" in your rig. Off a little here, off a little there. I would adjust it to specs per FSM, they must have had a reason for it.

Good luck.