Rear end clunking noise ( I know rear end)

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Nov 18, 2006
Roxborough, CO
OK guys,

I drove the 4Runner yesterday with the 37's for the first time, boy is that thing tall. Anyway I am driving it everywhere to break in the springs and hopefully get some sag in it.

So here is the problem, when I accelerate rapidly or stop rapidly the rear end makes a clunking sound. Sort of like the third member is being pushed up or down and then setting in place. There seems to be some axle rap going on, as I rock the truck back and forth by pulling on the bumper you can see the pumpkin move up an down.

Does anybody have an idea on what it may be??

Here is the set up, 85 4Runner, 5" Marlin USA springs mounted to 2" lift shackles (soon to be removed) shocks are in the stock position.

Thanks for any help you may send my way.
Could be a worn out u-joint at the axle end of the driveshaft. Did you just lift this rig? Maybe it was worn before, but not too noticeable with the stock driveshaft angle, and now with a steeper angle it is causing the noise???
Thanks for all the info guys, most of you were right on the nose. Found the issue, seems that the U bolts came loose after driving only 20 miles. My friend torqued them to the correct specs and we planned on checking them again in about a 100 miles but now I think everyday for about a week and then once a week for a month or so.
It might be worthwhile to put some locktite on there after you get them tightened down....

Also, did you reuse the locknuts/lockwashers?
The bolts are staying tight, the U bolts are stretching a little at a time. I checked them again last night and they were dead on, same torque spec I set them to on Friday. Looks like they are done stretching.

I will add some loctite once I feel everything is ready to go.

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