clunk in zg while driving on highway

[Farcall]

Hi All,
When driving my ZG on the road at highway speeds it will sometimes give a clunk, sound a bit like something disengaging or dropping out off gear. Its an auto behind a 4.0lt.
Any thoughts?

[Doctor W]

How heavy/noisy a clunk????

It could be the torque converter locking up/unlocking like it's suppsed to.......but you can hardly hear/feel it unless you know when/how it's suppsed to work.

[Farcall]

zg noise

The sound is quite harsh and will only happen once a trip and every so often. Not under load of any kind. The car does not hesitate. My jeep has over 320000k on it and I dont know the service records( havent had it long) for the gear box.

[ZJ from WA]

possible slip yoke needing greasing. mine also does this.

[turbomart]

possible slip yoke needing greasing. mine also does this.

Yep, or maybe torque converter lock-up.Try pressing button preventing t/c lock-up & see if that stops it.

[Doctor W]

Yep, or maybe torque converter lock-up.Try pressing button preventing t/c lock-up & see if that stops it.

That button is to "lock out" Overdrive engagement............Torque Converter lock-up is not a driver controllable thing.

[drover]

If you don't know it's service history, the best bet is to take it to an Tranny Mechanic who you trust and get him to do a service on it, so long as he's got a code reader that should at least show up if the box has a problem or whether it's elsewhere. If you have rev changes when you hear the clunk then I would say it's the box otherwise its somewhere else.

[turbomart]

That button is to "lock out" Overdrive engagement............Torque Converter lock-up is not a driver controllable thing.

Actually that button on most older cars which used to be labeled 'overdrive' or 'power mode' is actually just a t/c lock-up disable.So called 4 speed "overdrive" autos were in fact 3-speeds with t/c clutch.The WJ/G auto is a true 4 or 5 (if enabled) speed trans with additional t/c clutch ie it has 2 complete epycillic gear sets instead of 1. one epycilllic gear set gives a combination of 3 forward gears & 1 reverse depending on what element you lock ie ring gear ,satelite gears ,etc.
Anyway, even on WJ/Gs that button mainly serves to prevent t/c lock-up (t/c clutch cannot handle application under load) as with towing etc.