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Thumping in full time 4wd when accelerating.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=3&t=50332		 Page 1 of 1
Author:  e_poirier2004 [ Thu Feb 18, 2010 10:36 pm ]
Post subject:  Thumping in full time 4wd when accelerating.
I have a serious thump (like a rubber muffled thump) when I accelerate in full time 4wd. It's only one thump and it does it again if I decelerate and accelerate again. I don't have that in 2wd. My rear lower control arms were changed last fall. I installed an OME lift about a month ago. Any idea anyone?
Author:  dgeist [ Thu Feb 18, 2010 11:24 pm ]
Post subject:  Re: Thumping in full time 4wd when accelerating.
e_poirier2004 wrote:
I have a serious thump (like a rubber muffled thump) when I accelerate in full time 4wd. It's only one thump and it does it again if I decelerate and accelerate again. I don't have that in 2wd. My rear lower control arms were changed last fall. I installed an OME lift about a month ago. Any idea anyone?


I have a similar problem currently and I'm thinking motor-mounts:
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=49882
The 4Wheel-only thing might be a red herring. Mine was like that at first, too, but eventually got more frequent and now sounds like a loud rattling in the engine bay any time the transmission is in gear and I'm stopped.

Check around that thread any others for ways to troubleshoot the motor mounts (pry-bar and a buddy or visual inspection, etc.) Also, it wouldn't hurt to inspect all the CV boots. The front drive-shaft has a tendency to tear its boot where it leaves the transfer case for no good reason and get dirt/debris in the joint and wear it prematurely.

Dan
Author:  InCommando [ Fri Feb 19, 2010 5:48 am ]
Post subject:  Re: Thumping in full time 4wd when accelerating.
That is a common u-joint/cv joint failure symptom, too.
Author:  e_poirier2004 [ Fri Feb 19, 2010 5:50 am ]
Post subject:  Re: Thumping in full time 4wd when accelerating.
Same thing here when I'm stopped. I hear some rattlling. Also, when I'm accelerating at WOT, I feel something shudder around 3000 rpm. Make sense for the engine mounts. How do you check those?
Author:  e_poirier2004 [ Fri Feb 19, 2010 6:01 am ]
Post subject:  Re: Thumping in full time 4wd when accelerating.
There's one test I've done that make me think it might not be the engine mounts. I put the truck in drive and hold the brake with one foot and press on the accelerator with the other foot and no thumping. I release the brake and get the wheels turning and then I get the thump!!! I'm thinking around the frond diff. No thump whatsoever in 2wd. I do get a vibration when I stop and I'm in gear.
Author:  Jackson02 [ Mon Feb 22, 2010 9:50 pm ]
Post subject:  Re: Thumping in full time 4wd when accelerating.
Quote:
I have a serious thump (like a rubber muffled thump) when I accelerate in full time 4wd. It's only one thump and it does it again if I decelerate and accelerate again. I don't have that in 2wd. My rear lower control arms were changed last fall. I installed an OME lift about a month ago. Any idea anyone?

mine did me same thing turned out to be the front driveshaft
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