I have a 2006 f-150 supercrew 2wd. Every time I stop there is a clunk in the rear. When I move forward it clunks again. If I stop in neutral it is smooth, but when I start it will clunk again. A rolling stop does not do it. My mechanic can not find anything wrong. Any ideas?

 

Sounds kinda like a bad U-Joint.

 

I agree it sounds like a U-joint but they said they are tight.

 

Check U-joints under load - put the truck into parking, and try to rotate (slightly - you don't want to break it) the driveshaft with a metal bar or tire iron. You should be able to see some free play.

 

Many years ago I had an F100 Ranger that was making a clunking sound from the rear. I was on my way to the shop, to replace the u-joint, when my rear wheel rolled past me as I was stopping for a traffic light. The truck never wobbled, or otherwise drove erratically, so I was not aware that the rear lug nuts were loose, thus the tire coming off. Just a thought...

 

its probably the slip yolk. if so, it just needs to be re-greased. i have the same problem with mine. im too lazy to do it.

 

Maybe some repetitive side load on the rear axle. The axles do have some lateral clearance that allows the them to slide in and out sometimes causing a fairly loud clunk....no big deal, just annoying.

 

thanks for all the tips, but with all of these ideas.... why does it not do it if I slip the tranny into neutral?

 

In neutral there is no pressure on the drivetrain, hence, no noise.

 

2nd vote for the slip yoke, my Bronco does the same thing in gear and nothing in nuetral. plus its a cheap fix.