I have a 93 XJ 4.0 with 215k on it. Runs and drives great however driving around town in the 45-55mph range I get a small jolt from the rear axle when I let my foot off the gas. I can sometimes mitigate it by very slowly and purposely letting my foot off the gas but just under normal driving conditions its fairly consistent. Doesn't happen below 45 and rarely over 55. I did have a 3 inch lift installed recently but this issue was definitely occurring prior to install and if anything it has actually slightly improved since the lift.

Any thoughts?

Thanks

 

Just theorizing here. Below 45mph your rpms are keeping tension on the drivetrain. Above 55mph the same. In between your in OD where I believe it's possible that slack in the drivetrain could be enhancing an issue you may have with u-joints,slip yoke,rear axle assembly.

 

That's a good thought Earl. At 45 the TC lockup clutch engages, so RPMs would be lowest.

Is the issue the same on flat ground vs. climbing a hill?

 

Thanks for the replies.

I haven't noticed whether it happens going up hills or not. I'll have to pay attention when I head up into the mountains this weekend.

When I had the lift installed I had all the u-joints and drive shafts inspected and they said they were good to go. Axle assembly is an interesting thought...

"At 45 the TC lockup clutch engages, " That's really interesting because it happens very specifically beginning at 45. Letting off the gas at 35-40 is smooth as butter....

 

There would be more backlash feel with the torque converter locked up. When it's not locked up the fluid coupling in the TC would be absorbing some of that. You can briefly unlock the TC clutch by tapping the brake with your left foot while still on the gas and you'll see the RPMs jump up. You could possibly test the theory by unlocking/letting off the gas vs just letting off. Also, you could lock it in third and test as well. TC lockup is around 40mph in third. This is true at least in my '00. I'm not sure if your TCM would act the same in third or not.