Pronounced "thunk" in Jeep Laredo ('05)


#1

I wanted to know how you can isolate differential, universal or tranny noise in this truck. I am getting a pronounced “thunk” from the underside of the truck if I accelerate and then let off the gas…it happens about 2-3 seconds after I take my foot off of the accelerator. Thanks!!


#2

You’ll need a 4-point lift, one where you can walk under the vehicle with the wheels suspended and free spinning. Grab the driveshaft and twist it back and forth. Follow the sound. Look at the play.

If it turns out that you suspect the differential, you can remove the cover (after draining) and look at the wear on the ring gear. If it isn’t centered and even, the pinion isn’t properly adjusted (wear may be a factor). Because of the 2-3 second delay, I’m thinking the bushing for the pinion gear is worn and the gear is sliding in and out too much as the load is reversed. But I’m truely wildly guessing. A universal joint would be much more likely.


#3

You don’t get a thunk when the truck is moving very slowly, and you move the gear shift lever from Drive to Reverse to Drive? back the truck onto ramps. Set the brakes, chock the front wheels. Don’t get under the truck. Look at the drive-line, differential, spring mounts,etc as the driver, engine idling, moves the shift lever from Reverse to Drive to Reverse. Have the driver rev the engine and let off, rev, and let off. Does anything seem to move too much? Does anything hit?