Knock on Acceleration
 

Hello All,
I have been noticing a knock on acceleration. It does it consistently under every normal take off from a dead stop. It seems the worst when shifting from Neutral to Drive. I notice the knock when going through the rpms in 1st and then after the shift from 1st to 2nd.

I took a look and everything seems Kosher underneath the truck. I had someone try playing with the exhaust, but it didn't budge.

Any ideas? I'm thinking a u-joint on the drive shaft.

Also is there zerks on the drive shaft for grease?

Thanks guys!

That sounds like a Super Duty clunk. Lightly grease your slip joint.