Bad "thump" when starting off... HELP!
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Joined: Nov 2003
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Bad "thump" when starting off... HELP!
Hey guys. Thanks ahead of time for any input you give me. I have a problem here. I have a 99 Superduty regular cab with a 4" lift. When starting off from a stop i have a loud annoying thump that occurs. If i "roll" off of a stop at a light it doesnt happen. As soon as i give it gas and put some torque to the drivetrain... i get a "thump" in the rear it seems. I can see the rear jump when this occurs.
Now i know a bit about trucks so i checked the u joints... they are good. There is NO carrier bearings to worry about cause it is a regular cab. I pulled off the rear diff cover and nothing is broke and there is no metal in the oil. It is an open diff too, just so you know. The rear leaf springs are good and the u-bolts are tight. There is NOT a broken spring in the rear.
Now my trans IS slipping and i am assuming it is from within the trans. But i guess it could also be in the t-case? ANY help would be greatly appreciated. Thanks guys!
Now i know a bit about trucks so i checked the u joints... they are good. There is NO carrier bearings to worry about cause it is a regular cab. I pulled off the rear diff cover and nothing is broke and there is no metal in the oil. It is an open diff too, just so you know. The rear leaf springs are good and the u-bolts are tight. There is NOT a broken spring in the rear.
Now my trans IS slipping and i am assuming it is from within the trans. But i guess it could also be in the t-case? ANY help would be greatly appreciated. Thanks guys!
Logistics Pro
Joined: Aug 2007
Posts: 3,974
Likes: 17
From: Millersburg, OH
You can try greasing the slip joint. Don't know if that will help but it's at least simple and cheap to try.
Slip joint regreasing
Slip joint regreasing
Of the next Riffraff East
Joined: Oct 2004
Posts: 8,679
Likes: 2
From: Concord NC
Unless you are in 4WD, the transfer case wouldn't be an issue. the slip joint could be it, but usually shows more when going to reverse. If your tranny is slipping, that could be your problem. Change you fluid and filter if you haven't as it may help some.
New User
Joined: Jul 2008
Posts: 15
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I have a similar "thump" as well in my '04 F250SD, KR, 6.0 PSD, Limited SLip.
I'm not totally convinced that this is the problem with mine, I'm still researching it, but this info from the "Tech Folder" might be helpful for you:
Rolling Chassis FAQ
Q: Why does my truck clunk when taking off from a stop?
��� A: Common problem usually lies with the slip-yoke on the rear driveshaft. Usually removing the driveshaft and lubing the slip yoke can relieve that problem. See this site for an excellent how to. Slip joint regreasing
Hope this helps...let me know what you find, I may be following you down that road soon.
I'm not totally convinced that this is the problem with mine, I'm still researching it, but this info from the "Tech Folder" might be helpful for you:
Rolling Chassis FAQ
Q: Why does my truck clunk when taking off from a stop?
��� A: Common problem usually lies with the slip-yoke on the rear driveshaft. Usually removing the driveshaft and lubing the slip yoke can relieve that problem. See this site for an excellent how to. Slip joint regreasing
Hope this helps...let me know what you find, I may be following you down that road soon.
Senior User
Joined: Sep 2002
Posts: 487
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From: Hibbing, MN
I had the same problem on a different truck. Tried greasing the yoke, new U joints the whole 9 yards. It turned out the slip yoke had a twist in the splines. It was very slight but after it was replaced the thump went away. Take the drive shaft out, clean the yoke and look down the splines. If they're torked at all replace it and your problem will be solved.
Doug
Doug
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