Clunking when getting on and off the gas

[68mustang]

My 73 has a 3.5" suspension lift and 2" body lift. It has a pretty decent clunk with getting on and off the throttle. There rear drive shaft has a steep angle to it. I have checked u joints and tight bolts. Could this be a problem with the shaft angle? Do people have to do some kind of drop kit?

 

[73azbronco]

engine, tranny?

Engine tranny mounts?

 

[okie4570]

Axle wrap?

 

[Speedrdr]

Is your rear suspension lift a new set of springs or a lift block? I have seen the locating pin on the block shear off and cause a clunking noise.

Randy

 

[DirtDonk]

A picture of your setup would help. But in lieu of that, how steep is the angle? A 3.5" lift should not be overly steep. I've found that when they are, the rear pinion is pointing too far down and needs corrective measures such as shims under the leaf springs.

Another thing, probably one of the most common reasons actually, is the slip joint in the driveshaft binding up. The only way I could get rid of my clunk was to pull it apart and manually grease the splines.
However, most of the time I think a slip joint is more of a clunk when you start. But not so much when you let off the gas.

So you'll have to be the one to do all the detective work. We can't see it or hear it, so it's all on you. We can only point you in different directions.
One of those directions would be to do with the body lift.
Look at your transfer case shifter to make sure it's not just touching the tunnel where it comes through.
Where is the exhaust run? Any part of it close to the body or frame?
What about the back of the driver's side cylinder head? Close to the firewall?
Steering shaft? Do you feel the clunk through the wheel, or is it all in the seat-of-the-pants coming through the floor?

Paul

 

[Yeller]

Locker?

 

[JSBX]

Also check your spring u bolts to make sure they are tight. That should be part of routine maintenance.

 

[DirtDonk]

You said you “checked the u-joints and tight bolts” but does that mean you checked the big U-bolts around the springs?
As said, that’s a good place to check.
Not only that though, but check to make sure that your spring perches are not rounded over on the ends. That used to be a common thing with Broncos and one of the sources of clunks back in the old days.