Bryn Jones
NAXJA Forum User
- Location
- Plymouth, England
Hi all,
I'm looking for some help with my XJ. It's a RHD 1998 with the 4.0, AW4 and 242 transfer case, currently on 202,000 miles. Completely stock, with tow package which gives me an auxiliary transmission cooler plumbed in line with the transmission cooler in the radiator.
For years now I've been chasing an intermittent torque converter lockup. I've finally pinned down that it's only happening when the Jeep is thoroughly warmed through (it doesn't overheat). When the Jeep is running cooler, the lock up works 100% perfectly.
If I can get it to lock, it will never unlock when it shouldn't - it will only unlock if I brake, downshift or slow down too much. That means I could happily drive 100 miles at a steady speed with it locked up just fine, if the Jeep was running cool when I started. If the Jeep heats up in that time, there's a strong chance that it won't lock up again if I the TC has to unlock for any reason.
I have installed a light to indicate when the TCU is sending 12V to solenoid #3, and this light shows that when cool it is behaving perfectly. However, when the torque converter is not locking up, the indicator light shows that 12V is still being sent like it's supposed to.
To me, this rules out any electrical issues with things like the TPS, brake switch, NSS etc.
The light is connected at the TCU output.
I replaced the solenoid about 9 months ago with a Rostra one, but this did not fix the issue. The new solenoid tests as having between 15-18 ohms resistance at the plug in the engine bay, depending on temperature.
I've also recently done 4x drain and refills of the transmission, with no change.
In summary:
I'm looking for some help with my XJ. It's a RHD 1998 with the 4.0, AW4 and 242 transfer case, currently on 202,000 miles. Completely stock, with tow package which gives me an auxiliary transmission cooler plumbed in line with the transmission cooler in the radiator.
For years now I've been chasing an intermittent torque converter lockup. I've finally pinned down that it's only happening when the Jeep is thoroughly warmed through (it doesn't overheat). When the Jeep is running cooler, the lock up works 100% perfectly.
If I can get it to lock, it will never unlock when it shouldn't - it will only unlock if I brake, downshift or slow down too much. That means I could happily drive 100 miles at a steady speed with it locked up just fine, if the Jeep was running cool when I started. If the Jeep heats up in that time, there's a strong chance that it won't lock up again if I the TC has to unlock for any reason.
I have installed a light to indicate when the TCU is sending 12V to solenoid #3, and this light shows that when cool it is behaving perfectly. However, when the torque converter is not locking up, the indicator light shows that 12V is still being sent like it's supposed to.
To me, this rules out any electrical issues with things like the TPS, brake switch, NSS etc.
The light is connected at the TCU output.
I replaced the solenoid about 9 months ago with a Rostra one, but this did not fix the issue. The new solenoid tests as having between 15-18 ohms resistance at the plug in the engine bay, depending on temperature.
I've also recently done 4x drain and refills of the transmission, with no change.
In summary:
- TC won't lock when Jeep is hot
- Solenoid replaced - no change
- Indicator light shows TCU is sending 12V as it should
- If TC does lock, it never unlocks unpredictably
- No CEL, ever
