Torque Converter Questions

Hey!

I have a question regarding the "normal" TC behaviour. My 1998 4.0 AW4 had some issues regarding lockout (and general shifting issues) which were all resolved by replacing the solenoids a few weeks ago. (seperate thread here: https://www.naxja.org/forum/showthread.php?t=1160110)

Something I noticed recently is when I drive normally/slowly everything works as expected, the TC locks up just after 80kph in either D or 3rd. This past weekend I was towing my caravan and needed to give it a bit of right boot through the gears, and once I was at cruising speed I noticed the TC was not locking up.. At the next chance of stopping I was able to accelerate easier through the gears and bam, TC locked up correctly. I managed to verify this a few times, accelerate hard then TC fails to lock up when reaching cruising speed, accelerate easier and TC locks up correctly.

So my question is: Are there scenarios where the TC would not lock up? What would cause the TC not to lock up under hard acceleration through gears and finally going easy at cruising speeds? :viking:

From my knowledge of other cars (I haven't been a chrysler mechanic for a while) the torque converter lockup will only occur under a specific load/rpm limit. So if you're 'cruising' but you're loaded down, the TC might not lock up. You can probably get it to shift into lockup by accelerating above your speed, then back off the throttle to your desired speed.

I had some issues with my AW4 not shifting into gear until it was way too late under normal conditions a few months back. 1st to 2nd was fine, 2nd to 3rd would tach out to 3500, sometimes close to 4000 under light throttle, then slam into 3rd, then lockup and 4th immediately. I replaced the TPS and it's been great ever since. What's even more peculiar is that the TPS tested perfectly fine through the whole range (used a voltmeter at the ECU). After testing everything else I replaced the TCU on suspicion, but it still shifted the same. On a whim I swapped the TPS and everything was great after.

I assume you already have adjusted the transmission cable?

Agreen said:

I assume you already have adjusted the transmission cable?

Click to expand...

Thanks for the feedback. I have actually not adjusted it yet.. My machie adjusted it some time back but I will give it another shot again.

For some reason I was also suspecting the TPS, as I figured heavy throttle input might be causing some issues. Also, the ol' Jeepie is a little low on power in the 2000rpm range, almost feels like a "flat" spot. If I get caught with the caravan at 2000rpm thats me, will have to give it serious foot to go anywhere.

I will pull the TPS and test the sweep and see what comes up. Pity I don't have an analog meter though, might be worth getting one.

So I have adjusted the TV cable. Generally speaking the gearbox shifts much nicer now but it made now difference in the lockout issues. Today, even under light throttle the TC did not lock out correctly, both in 3rd and D... Strangely after about 60 minutes of driving it locked up correctly for a few KM, then stopped again. Hoping the solenoid did not die again or maybe one of the plugs popped off. I will retest them again today.

Any other sensors I can check? Does the Gearbox speed sensor effect the lockup?

TPS sensor, brake light switch, NSS sensor can all cause issues with t/c lockup if they're telling the trans computer you're on the throttle, hitting the brakes, or have the shifter in a different position. Or a bad #3 t/c solenoid.