Xj transmission help

jeepn-jason

jeepn-jason

Well-Known Member
Joined
Mar 20, 2005
Location
Greensboro
I've got a 96 xj 4.0 aw4. Has 3.5" lift and 32" cooper stt on it. I've been having issues with the locking torque converter lately. It has never seemed to unlock when pulling hills or anything but when pressing the brake it always has. Here recently it has been staying unlocked at times. It mainly happens after driving for a while. Also would this have anything to do with how terrible the fuel mileage is? With an uncorrected speedo and mileage it's been adding up to around 12.5 mpg. All highway driving. I've recently tuned it up with good parts and have no difference in mpg.
 
Replace your brake light switch. I had an xj do the same thing. Trans shop said it was the input speed sensor. Replaced that $120 dollar part and still same issue. Replaced the tps because another scan tool showed it could be the problem. Still no good. $11 brake light switch and problem solved.
 
I was gonna start with the brake switch, as I've had a handful of times the cruise control hasn't worked, with hopes that it's related.
 
I bought mine at Autozone and it had the OEM part number on the piece in the box. Can't beet it for the price.

sent from my tin foil hat using menstral powers and espn
 
Installed the new brake switch this morning. I'll drive it after work to see how it does. Another question regarding the torque converter. Should it unlock on hills before downshifting? Mine never has since I've owned it.
 
I'm not sure if it should or not but has always down shifted and unlocked at the same time. I've had several Cherokees and they have all done it that way.
 
Had a 20 mile trip home from work tonight and it stayed locked. Cruise still didn't work but I'll figure that out later.
 
On the cruise control check the vac line just inside the passenger fender. It sits just right for the hood prop rod to crack the hard plactic line. Mine did that and the cruise would not set.
 
I checked the vacuum lines today and the electrical connections at the servo today. All seemed good. After driving it after work today I've diagnosed it as the switch being the issue. I can rock the switch from bottom to top and it sets every time. I'm gonna try to take it apart to clean the contacts.
 
My 98 had that problem. The switch contacts were nasty. Pulled the switch apart and cleaned the contacts and all was good after that.
 
Cool! Thanks for your help !!
 
Ok driving to work the converter unlocked again this am. I noticed if I kept pressure on engine it stayed locked. As soon as I lifted just a tad on throttle, the rpms would jump about 300 to 400. Apply throttle back and it would fall back down. I'm gonna throw a meter on the tcu this weekend to see what the solenoid is doing.
 
I'm still battling this issue. I've put a meter on the wires in the harness at the firewall going to the solenoids. They ohm out a 15 ohms hot so they should be good. Also noticed that when it happens the transmission won't kick down on hills unless I'm about 75% throttle. I'm kinda leaning towards the pts sensor at fault but not sure. I've adjusted the cable going to throttle body and replaced the brake switch so far. It really seems like an electrical issue because it doesn't do it all the time and seems to happen after driving for a bit.
 
jeepn-jason said:
They ohm out a 15 ohms hot so they should be good
Click to expand...

That is a red flag to me. 15 ohms is a ton in the world of electrical diagnosis.

I remember replacing quite a few AW4 valve body wire harnesses for solenoid codes and/or issues. I couldn't find the failure with an ohm meter, but only after I applied a load through the wires. (Used the individual circuits to ground a 12 volt bulb through when unplugged) Then I could see that the wire(s) had been fatigued and couldn't carry a load.

Check TP voltage @ closed throttle and verify the TV cable adjustment too
 
Ok finally got the tcu laying in the pass seat with the meter hooked to it. The solenoid 3 wire (white w a blk stripe) loses 12v when it unlocks. That pretty much tells me that the tcu is sending the command to unlock the converter, and the solenoid and wiring from tcu to transmission is ok. I replaced the tps last week with no change there either. I have the meter on the tps voltage coming into the tcu now and will check it on the drive home.
 
Thought I'd report that a replacement tcu from the junkyard took care of the problems I had.
 
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