Transfer Case

[rasouth]

About the only way to find the noise would be to hoist it on a lift (Not jack stands! You don't want the car to vibrate off jack stands), until wheels are off the ground, and let someone start the car and put into gear and press on gas as you search for noise. You might be able to locate the "clunk" noise better.

 

[Mbrooks420]

I think it’d be safer to do on jack stands and lay next to the car, then to run it on a lift. There’s hardly any chance (as in never) a vehicle would vibrate off my jack stands.

 

[Blue m&m]

Been running mine on stands all week. No problems.

 

[rasouth]

I was assuming that all four wheels would be off the ground, as on a lift, so you could check both drive shafts and the TC. If it was just the rear wheels, we all have done that.
If all four wheels were off the ground with jack stands, it's not just vibrating that is a concern. If the car changes gear and there's a jolt or lurches, jack stand tips over... Just a safety concern.

 

[Ronjm]

No I have front wheels on ramps & back on stands only back wheels in the air. The front drive shaft is disconnected.

 

[rasouth]

Start the car, lay on ground, have someone put car in gear and listen for noise. Try in forward and reverse gears and try out the TC if you can.

 

[Mbrooks420]

I’d have zero issues lifting all 4 corners on jackstands and running the drivetrain. If your stands are quality and in the correct place they won’t be disturbed by the rotational shock.

 

[drdoom]

Have you pulled the splined slip joint out and inspected / serviced it? You might as well do that while you have it on stands.

 

[Ronjm]

IveI got new u joints coming I will do it then cheers

 

[Ronjm]

Ok changed u joints, serviced slip yoke the clunk is less often now but still there.

 

[MrQ]

Hate to say it, but you might have a bad pinion bearing in the rear axle.When the bearing goes a bad a clunk under acceleration is heard as the slack is taken out of the pinion bearing and the pinion gets driven into the ring gear. Over time this will destroy the rear end.

When you gently accelerate, do you hear it? Do you hear it when in reverse?

 

[Ronjm]

Yes sometimes when accelerating gently but not in reverse.

 

[MrQ]

Yeah... I'm leaning towards pinion bearing.

 

[Ronjm]

If it was pinion bearing would there be some play in the drive shaft?

 

[MrQ]

Yes.The driveshaft would move forward and back a small amount, but with as tight as the tolerances are on those bearings we are only talking about (spitballing here) .050" You wouldn't be able to feel it unless it was really really bad. There may be some additional slop rotationally as well.

 

[Ronjm]

Well there is a very slight bit of play but I mean very slight does not seem there is anything wrong. I took it for another drive this morning & clunk (clang) is still there but not as often since I greased the yoke.There is a few loose heat guards on the exhaust but i can't see them being a problem.

 

[MrQ]

You'd be surprised what kind of noise loose guards will do. I wound up cutting off my top muffler heat shield because every time I started off in first gear the engine would lug a bit and make a huge rattle. Not saying that's your issue here, but don't discount them as making the noise.

Other thing I was thinking...Are you missing any bushings in the leaf spring mounts?

 

[410Fortune]

Usually with the truck in the air and running (I use 4 BIG jack stands and I point the truck AWAY from the shop/house) it only takes putting it in D and letting it idle to find the noise.
I have done this SAFELY many many times. It's not my favorite thing to do, but it can be done safely. I try not to go under the truck, but like I said usually it only takes about 5 seconds of the truck actually in gear and drivelines moving to confirm the noise is either what I thought, or something else.

Before you do that You should have somebody bounce the truck by the bumpers, rock it back and forth, bounce the suspension while you look around. Many times this will locate your noise
Next you should support the truck by the frame and let the suspension hang, get underneath the truck with a short pry bar and do a "shake down" test....usually this will find the looseness, bushing, joint, mount.
If you have a go pro or similar you can also rig up mounts to watch the suspected clunk location as you drive around, this is much safer then getting under a running truck
If all of that fails to locate the noise THEN I put the truck on 4 stands and have a helper stand on the brakes, start the truck, put it in D or R and try to spot the noise while the drivelines are moving, only get under the moving truck if ABSOLUTELY necessary. And NO LOOSE CLOTHING, long sleeves, belts, un tucked shirts, etc
SAFETY FIRST

On our trucks there are so many things that can cause a clunk, but usually they are not terrible to locate

 

[Ronjm]

Thanks guys I will have another go.

 

[Ronjm]

Another one I am going to change the rear diff oil what is recommended and do i have to get some friction modifier as well. I also noticed I have the rear end sag to one side could this be the problem as well?