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aw 4 tranny problems

posa88xj

NAXJA Forum User
Location
mariposa
Hey I got a 88 xj 4.0 aw4 4 speed auto.
awhile back I was towing a trailer with a side by side on it with the power switch for the tranny on. shortly after it started to slip almost it seemed, it just didn't have any power to the wheels and would rev up. so I threw it to 4 low and in 1st gear to make it up alil ways farther to park and unload the trailer. I was able to shift it threw the gears to make it home without the trailer. i messed around with the throtle valve cable some, and then took it to a buddy who has a shop, told him wat was up and he drove it and said it was one of the shift sylionids since it would start out in 3 or 4th gear. so the mechanice said id be fine shifting manualy till i got the parts. so I ordered up a new set of syloinoids and put them in the other day. and with no luck same problems. so today i tested the tcm with my dvom at the plug useing transonline article bout aw4 troubleshooting, and got intersting results. there is no power from the speed sensor, the tps, the D position in the selector level. i had constint power with or with out the brake depressed. had bad resitince from shift syloinid 1, no power to the tps supply. no voltage imput from the tps,. also down stream of where the inline fuse is, there is supose to be a resistor but all i see on mine is a plug that has been jumped by a paper clip. i have swaped between two different tps's i had but just read something todasy bout having to adjust them, is that true and how would that be done? also tonite i was drivin home and i shifted threw the gears like i have been and where i got to 45 mph the engine started sputtering and i lost D, and had to down shift to 3 and i couldnt get more then 40 mph and lower the 3 K rpm. at 35mph i would shift bak to D and would do ok till i hit 45mph and it would lose the gear and rev the engine... and if anyone has a picture of the plug resistor and fuse for the tcu that i could compare to would be great. Thank you very much for any info that can be givin.
 
Ok, with the TCU unplugged does it shift correctly? Specifically, do you have 1st in 1-2; 3rd in 3; 4th in D; reverse, neutral, and park? If so, then the problem is electrical in nature. If not, you have a hydraulic or mechanical problem.

Assuming you have the correct shifts with the TCU unplugged. Ok, you need to test and/or adjust the TPS--bookmark this website, it is invaluable for Renix XJs: http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

There are two fuses for the TCU, a 7.5 amp in the fuse block by the driver's left foot--don't worry about that one. There is a yellow wire that runs to the TCU--on that yellow wire is a 10 amp inline fuse--check it, it is critical.

Also, when was the last time you flushed the transmission? Fluid life is 30k miles IF IT IS NEVER OVERHEATED. Heat kill transmission fluid--I get a little suspicious when people have problems after towing--the heat thing--so if you can't remember when it was last flushed, or you don't know if it has ever been flushed, start with a visible inspection of the fluid--red, almost a pink color? How does it smell--burnt? How is the fluid level?

Post up what you find.
 
I have 1-2 and r, and park but not 3rd or drive when the tcu is unplugged. I just dropped the pan last Tuesday and the fluid was burnt, I have replaced it to the correct level but I haven't done a power flush yet. the fuses are both good, but i think the resistor has been removed, i can't seem to find it, and there is a plug by the inline fuse that has been jumped with like a paper clip or something. the lose of drive and engine sputtering maybe because my tps is out of adjustment or bad.
 
Search poor mans flush, you have changed about 3.5 quarts with by dropping the pan, you need to do about 9-9.5 more quarts.

Can you post up some pics of the plug and jumper arrangement?
 
I will try here right now. I work at a small shop that has a power flush machine that I can use, I just have to find the time to do it.
 
photo.php


photo.php
 
Did you try to post pics?

You need to use a picture host sight, then copy the IMG info and paste it in your post.
 


Looks right to me. It might look like a paperclip, but that's the resister and that's how its normally connected. If it were a paperclip you'd be shorting the +12volt power feed on the yellow wire to ground through the brake pedal switch. You can unplug it an verify with a meter if you want. I don't recall its value, but it should be at least a few thousand ohms. If the resistor is missing, it will cause the TCU to think you've got your foot on the brake pedal and unlock the torque converter.

Along those lines if the switch at the brake pedal is dirty (common) it will cause the torque converter to not lock up.
 
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so today i tested the tcm with my dvom at the plug useing transonline article bout aw4 troubleshooting, and got intersting results.

there is no power from the speed sensor, the tps, the D position in the selector level.

You shouldn't see power from the speed sensor. Its just a switch that closes once per revolution. If that was bad it wouldn't upshift at all. The D-position would point to a NSS that needs cleaned (search). I don't believe that's the cause of your problems either.

i had constint power with or with out the brake depressed

This leads me to believe that the brake switch is bad and needs cleaned up. Its the white white near the top of the pedal. The bracket its mounted in can be removed by removing the screw on the passenger side of the bracket. The switch itself can be popped apart and cleaned. If you've got a bad torque converter, having it unlocking as a result of this could cause excessive slipping and overheating.


Do your solenoids measure the correct resistance after replacing them? If not, you need to check the wiring from the TCU to the tranny for damage.
 
Well i just finished cleaning the nss but havent tried it as it got dark...i will check the brake switch tomorrow, and one of the solenoids did not read that much resistence, i forget which one tho, I will try all this tomorrow when i get a chance and see what comes of it.
 
also i shift it but moving the selector from 1-2, to 3 then to D, if that would make any difference with the speed sensor? but it does shift once i get speed from 3 to D, but i did notice the last time or two the last time i drove it it was a hard clunk when shifting to Drive, I dont know if that would point more toward the torque converter going out?
 
What happens if you start out from a stop with the shifter in D and the trans computer properly plugged in? Is it not starting in 1st gear?
 
not it doesnt seem like it is.....i have to get the engine up to 2500ish rpms, then its like it builds up pressure and then start to move slowly.
 
not it doesnt seem like it is.....i have to get the engine up to 2500ish rpms, then its like it builds up pressure and then start to move slowly.

That sounds like its trying to start off in 4th gear. You need to measure the solenoid resistances and voltages. Starting off in 4th gear is usually a bad solenoid (or wiring to it), no power to the trans computer, or a bad trans computer (somewhat rare). Use http://www.transonline.com/transdigest/magazines/1997-10/Shift%20Pointers/index.html as a guide. In particular you need to check the resistances at C13, C14, and C15 and the voltages on D14 and D16.
 
well this is wat i got when i tested the other day, c14 15ohms, c15 14ohms, c16 1.5 ohms, d 14 and d 16 i had 12 volts.... c16 is for the shift solinoid number 1....is that the one that controls 3 and drive?...the link doesnt show c13...what does that come from?
 
You have a bad shift solenoid or the wiring to it is shorted to ground somewhere. Didn't you post that you had replaced the solenoids already?

C16 is indeed for shift solenoid 1. That solenoid is turned on to give you 1st and 2nd. If its bad, trying to take off with the shifter in (D) you'll start out in 4th gear and then shift into third as you speed up. The low resistance you measured says the solenoid is internally shorted or you have damaged wiring.

1st gear ==> Solenoid 1 ON, Solenoid 2 OFF
2nd gear ==> Solenoid 1 ON, Solenoid 2 ON
3rd gear ==> Solenoid 1 OFF, Solenoid 2 ON
4th gear ==> Solenoid 1 OFF, Solenoid 2 OFF
 
yes i did replace them.... and i guess I will check the wiring next. from the motor side of the tranny, what is the posistion of the solenoids. is number 1 up front then 2 then 3, or are they not in order?
 
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