Need Help with my Rear Diff!!!

I have been having an issue with a clunk in my 3 for a while now. Got rid of most of the clunks/clanks up front by tightening the front skids and ucp. BUT, that dreaded clunk still was very loud almost every time I turned left. Finally got together with Larry (my fiance), and we properly diagnosed what is causing it. It's in the rear axle. This is what we found:

1) Driving over a drain/manhole that dips down and then back up, body flexes, and you can hear the rear end clunk loudly

2) Vehicle in park, in garage, turned off. If you go to the front bumper, and push the H3 up and down, on passenger/drivers side, you hear a clunk from the rear wheel. The clunk is louder on the rear passenger's side. You can physically feel it.

3) We took the rear tires off. There is definitely play in the end of the axles. You can move them up and down with your hands.

4) There is no visible sign of a leak on either side.

5) The clunk seems to go away when driven in the rain/wet roads-I know, it makes no sense at all!

6) There is no moan or whine driving....it drives perfect and is quite

We have not opened the inspection hole, to see what amount of fluid is in the rear diff. I'm waiting for it to cool down. We are thinking that it possibly could be bad bearings.

We would like to know a few things:

1) Does anyone have a blow out diagram of the rear axle with a rear locker?

2) Is this a common problem or has anyone experienced this before?

3) Are there any recalls/TSBs on this issue?

4) What would cause the end play that I have?

5) I would like to confirm the correct GM part # for the rear diff fluid for a rear locker. Dealer says it's all the same, no matter which H3 you have.

I do know that the previous owners towed a boat, but I'm unsure of the size of the boat. I'm not sure if that caused the damage.
Any information would be a great help! If it is something simple, and not expensive, I would like to repair it myself. Otherwise I will have to drive approx 4.5 hours to the closet dealership that may know what they are doing.
It is parked and I will drive my H2 in the meantime, until a complete diagnoses has been done.

It is not uncommon for an axle to make noise when sitting still and rocking or bouncing the vehicle. Much of this is the axle shafts inside the diferental sliding back and forth which is how a diferental works.

One other thing to check would be the front dif bushing as it can cause the kinds of noises you are discribing.

thanks for the reply, but the front bushing is fine. Looks brand new in there, no visible cracks, etc.

Good deal, and just to clerify, I wasn't discounting the the rear dif., just pointing out that it isn't uncomon to hear niose from them when bouncing or rocking the vehicle while it is sitting still. I've never noticed on a 3 how much noise they do or do not make.

Some in/out movement at the axle flange is normal. Up/down movement however, should be very limited. That points to a bad wheel bearing but, it would most likely be leaking all over the place. Differential bearings would make a grinding or whining, and probably not a clunk. The fact that you can bounce the truck in park and induce the noise tells you its something loose back there...probably suspension related. The H3 is an incredibly squeaky truck, and there's quite a few other things I would suspect before the rear axle (especially the differential)....

1. Loose upper and lower shock mounting bolts...very common.
2. Exhaust system hangers.
3. Rear hatch door adjustment.
4. Loose spare tire.
5. Loose spare tire mount (where it bolts to the door).
6. Something rolling around inside your storage compartment.
7. Something rolling around inside the rear door (loose jack).
8. Leaf spring noise (usually at the shackles or between the leafs)....spray em with your favorite lube.
9. Loose body mounts
10. Broken rear sway-bar link.

Have a fat friend (everybody's got at least one) stand on the rear bumper and bounce it why you lay underneath with a flashlight. Also...apply the brakes and repeat the bounce test...it could be worn brake pads floppin around in the caliper. There are supposed to be little springs on the pads to prevent this but sometimes they are missing. If all this checks out...then I'de look at the axle itself. My money is on a loose shock.

4speedfunk said:

Some in/out movement at the axle flange is normal. Up/down movement however, should be very limited. That points to a bad wheel bearing but, it would most likely be leaking all over the place. Differential bearings would make a grinding or whining, and probably not a clunk. The fact that you can bounce the truck in park and induce the noise tells you its something loose back there...probably suspension related. The H3 is an incredibly squeaky truck, and there's quite a few other things I would suspect before the rear axle (especially the differential)....

1. Loose upper and lower shock mounting bolts...very common.
2. Exhaust system hangers.
3. Rear hatch door adjustment.
4. Loose spare tire.
5. Loose spare tire mount (where it bolts to the door).
6. Something rolling around inside your storage compartment.
7. Something rolling around inside the rear door (loose jack).
8. Leaf spring noise (usually at the shackles or between the leafs)....spray em with your favorite lube.
9. Loose body mounts
10. Broken rear sway-bar link.

Have a fat friend (everybody's got at least one) stand on the rear bumper and bounce it why you lay underneath with a flashlight. Also...apply the brakes and repeat the bounce test...it could be worn brake pads floppin around in the caliper. There are supposed to be little springs on the pads to prevent this but sometimes they are missing. If all this checks out...then I'de look at the axle itself. My money is on a loose shock.

Click to expand...

This may help. The lower shock bushings have been known for premature wear too. But that's in anothe F5 thread.

http://www.hummer4x4offroad.com/for...8-61-001A-Underbody-Squeak-Creak-Crunch-Noise

Here's a squeaky link...

http://www.hummer4x4offroad.com/for...-03-09-004C-Squeak-Noise-from-Rear-of-Vehicle

Can't find F5's shock clunk thread.

4speedfunk said:

Some in/out movement at the axle flange is normal. Up/down movement however, should be very limited. That points to a bad wheel bearing but, it would most likely be leaking all over the place. Differential bearings would make a grinding or whining, and probably not a clunk. The fact that you can bounce the truck in park and induce the noise tells you its something loose back there...probably suspension related. The H3 is an incredibly squeaky truck, and there's quite a few other things I would suspect before the rear axle (especially the differential)....

1. Loose upper and lower shock mounting bolts...very common.
2. Exhaust system hangers.
3. Rear hatch door adjustment.
4. Loose spare tire.
5. Loose spare tire mount (where it bolts to the door).
6. Something rolling around inside your storage compartment.
7. Something rolling around inside the rear door (loose jack).
8. Leaf spring noise (usually at the shackles or between the leafs)....spray em with your favorite lube.
9. Loose body mounts
10. Broken rear sway-bar link.

Have a fat friend (everybody's got at least one) stand on the rear bumper and bounce it why you lay underneath with a flashlight. Also...apply the brakes and repeat the bounce test...it could be worn brake pads floppin around in the caliper. There are supposed to be little springs on the pads to prevent this but sometimes they are missing. If all this checks out...then I'de look at the axle itself. My money is on a loose shock.

Click to expand...

Thanks for the info!
The 3 only has 24K on the clock.
I don't believe it would be the shocks, because at first I did, but just replaced them a few weeks back...they were soft.
Brakes all look good, springs are all still intact.
I will take another look in the back, see if the sway bar link is gone. I haven't been able to find anything loose as of yet. I have checked everything else you have listed.
I don't think it's the Diff itself, but possibly wheel bearings at the wheel. I'm gonna pull the fill plug and see if there is any fluid in there.....

When bouncing the truck in the front, the noise is coming from the wheel flange. You can hear and see it move.

I also have creaky leaf springs, but just lube them with fluid film and it goes away.....that doesn't bother me at all!

If I might ask a potentially stupid question. If the 3 has 25K on the odometer, why not just take to a Hummer friendly GM dealer?

why not just take to a Hummer friendly GM dealer?

Click to expand...

Good one, Port!

2007HummerH2 said:

If it is something simple, and not expensive, I would like to repair it myself. Otherwise I will have to drive approx 4.5 hours to the closet dealership that may know what they are doing.

Click to expand...

Before you pull your hair our (if it's not to late) make sure you don't have anything in the storage compartments in the back and the jack is tightened down good.

Portager said:

If I might ask a potentially stupid question. If the 3 has 25K on the odometer, why not just take to a Hummer friendly GM dealer?

Click to expand...

Unfortunately, I do not have a Hummer friendly GM dealer near me that I would trust. The close one has screwed up many of my other vehicles. It will usually come out with more problems than it went in with. Other dealers will not service a hummer because I didn't buy it from them......now I know they are not supposed to do that....but they do.

It's going to be a 4-5 hour drive for me, so if I can fix it less than what gas costs, I'm all for it

storage compartments are empty and jack is tight.....it is something loose in the rear of the vehicle, just haven't found it yet. The weird thing is that the clunk/clank noise goes away with the wet weather. Now this is not a hard to hear clunk, it sounds like you are taking a hammer to one of the body panels....that is how loud it is.

OK, I missed the part about the 4.5 hr drive. I said it was a potentially stupid question.

Since you can hear it by bouncing the front, if you can crawl under there and hold a length of hose up to your ear (or use a stethoscope) and the other end to various spots you should be able to isolate the source of the noise. That should help diagnose the problem.

Fat guy and a flashlight is easier.