My truck makes a knocking sound and vibrates like hell. No its not the u-joints. Its really bad at about 40kph, but is felt and heard all the way from start to 150kph. I can push on the driveshaft by the steady bearing and it moves quite abit (the rubber part), like 3/4 of an inch. Is this normal play for the steady bearing? Any other thoughts on what the knocking could be?

 

Ok... I gotta ask... what's a steady bearing??? I've been thru my truck front to back and never heard of it.

 

On crew cab long box trucks, the drive shaft is two pieces. Its a part thats in the middle of the two shafts, that supports it to the truck.

 

Carrier bearing........... And it would be my first thought.

 

Carrier bearing.... that's the name I knew it by...

 

Sounds like a carrier bearing problem to me as well. If you want to duplicate this problem on a smaller scale, take an air wrench, 2 extensions and 3 u-joints (one on the driver then an extension, then a u-joint then the other extension and then another u-joint) stick a socket on the end and try to remove or tighten a bolt and watch the center u-joint, if it is not securely fastened in place to something (like how a carrier bearing is supposed to be) then it is going to go crazy jumping around.

This will duplicate the setup of you drivetrain from output of the trans to the rear end.