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black4.7H.O. 03-08-2011 12:50 PM

Thumping Noise
Hi Everyone, in my WJ (details in Sig) under hard acceleration, wet or dry road, I notice a thumping noise that I can reproduce every time. Under 3/4 throttle it doesn't happen but under WOT at all. The noise is like a consistent fast beat not like as if gears were stripping and you had it thumping erratically. You can feel it from the Drivers seat. Normal acceleration is smooth no problems no noise.

It doesn't seem to be Motor related as it will rev with no issue, coasting in N is smooth.

I checked the Forum for noises and found one from around Feb-Mar 2010 where the person found that it was a cross member the other had exhaust banging.

It makes me think of Trans slippage, yet the Jeep pulls the same as it did with 90k on it... While I'm talking trans, on occasion it in the morning if I jump in put it in gear and gas it, it feels like a manual car where trans/clutch isn't engaged, but if i wait 10 seconds, its perfectly normal...

The bushings on the suspension, front and rear sway bars, are aftermarket and I grease them often. I was also thinking that with the rear squatting and the front picking up maybe it was that but If I mashed the gas till 100 it makes that noise the whole time...

I can post a vid at some point if that helps.

Shes got 106k with normal fluids changes TC and Diffs (by Jeep with the Mopar fluids) as scheduled.

This is my first AWD/4WD vehicle so if its something simple go easy :).

Any Ideas? Thanks all.

2005JGC 03-08-2011 02:32 PM

Re: Thumping Noise
u joints?

Frango100 03-08-2011 03:27 PM

Re: Thumping Noise
Trouble shooting noises is not so easy. Would be a good idea to make a video, so that we can have a better idea. You said that it is not engine rev related, but is it speed related? When the noise is there during WOT only, it seems to be power related and probably is some play somewhere in the drivetrain. Do you have Quadra Drive?
The late transmission engagement in the morning is caused by trans fluid flowback from the torque converter into the sump. It takes some time to fill up the torque converter and until the power can be transferred. Sometimes the problem is in the round spinup filter inside the trans. But also some other internal leaks can be present, which causes the flowback.

black4.7H.O. 03-08-2011 04:24 PM

Re: Thumping Noise
Hey thanks guys,

200JGC Haven't inspected the U joints, will check 'em out today or tomorrow.

Frango100 It is Quadradrive. I was also thinking some where in the drivetrain.

Wow, thanks for the info on the TQ converter, I didn't know that. Does that man its having issues or its just character trait or even fixable? That issue has stayed the same and hasn't gotten any worse so I'm going hope it stays that way.

Ill work on a Video on the ride home.

Frango100 03-09-2011 06:14 AM

Re: Thumping Noise
U-joints or CV joints can be your problem. Also heard from one of the other members about the chain in the T-case, which was worn and could slip under certain circumstances. I would also check the diff and T-case fluids for metal particles in it.
Regarding the tranny, mine is doing the same and i have to change fluid/filters soon. This late engagement doesn´t harm the tranny according jeep service bulletin and was caused by the return filter. Many years ago they already modified this filter, but still i hear about this problem. Can be that aftermarket filters cause it, but not sure.
I was asking about the Quadra Drive because of the special additive which should be added to the diffs. But when they would have forgotten to put this in, you would have problems with noises when making turns, so not applicable to your situation.

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