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The Hummer Knowledge Base

Troubleshooting Noises:

Rattles: (Whistles below)

I had a lot of rattles that I sorted out but not on a gasser. Here is what I found:

Shields under the truck, fuel tank, tcase --> If bent can contact the truck

Exhaust pipe heat shields-->If clamp comes loose can rattle at certain rpm's and bumps

Rubber isolators on exhaust pipe - worn out and missing --->rattle

Squeaks on bumps, turns and body twist --> loose body isolator, usually front driver side, this should be 90 ft-lb tight.

Broken transmission dip stick support (under dog house) --> Rattle

Missing wave washer, front or read to hooks --> clank over bumps

Dry /worn ball joints --->Creaking (like rusty door) on hard turns

Cracked muffler, inlet or outlet pipe weld -> rattle

Broken CTIS compressor isolator mounts -> clunk over bumps

Worn or broken headlight isolators -> clunk over bumps

Loose brush guard (as in loose with pins installed) -> clunk over bumps (fix this by shiming one mount bracket so as to force the guard to twist in order to insert the second pin or by tightening the bolt through the himge so as to squeeze the guard on one side.

Broken exhaust header head shield -> clunk over bumps and when stopping engine.

There are some more but these are the initial ones that come to mind. (i have seen all of the above in my trucks). I am sure there are others but these are what I have come across.


Check the fit of the center hood snubber and the brackets on the hood.

Check the body mount bolts as someone suggested.

Check the control arm bushings.


Add to it a parking brake rattle when idling. The shifter rattle when driving. Both are diagnosed by holding the levers and the rattle goes away.

Any aftermarket items are always suspect.

I have had battery tray rattle from nuts and washers falling into it and bouncing around. I have had HUMMER DEALERS leave all types of tools in the engine compartment .... 1/4 ratchet wrenches, screwdrivers. When you work in the engine compartment you will understand how this occurs ..... no space to rest tools or parts yet you are standing on engine components to reach the item you are fixing.



I have a strange whistle in the truck which can be heard from about 40mph onwards, I cant quite find it, I thought it was up high at the top of the glass... Its a bit annoying on the freeway, have any of you guys experienced anything similar?

Before you tear out the windshield, which usually breaks, verify that is your problem. I guess you could spray Windex around the seams, drive fast to get your noise and then have your passenger see if it bubbles anywhere around the seams. Never did this, but, in theory it should work.


If it is the windshield, pop it out and apply sealant between the seal and the glass, then where the seal meets the frame. The manual states that this is the way it is to be done. Often people just dry fit the seal to the glass and frame when replacing glass, doesn't seal properly.

Richard S.
1997 HMCS's

Another way to test where the noise is coming from, if it is the window, is to tape around the outside top of the window with small 2" strips of masking tape. If the window seal is the problem the noise should go away when fully taped. Then drive around and remove one small piece at a time until you can hear it again - now you know exactly where the seal has failed.

As noted above, removing windows often breaks them. I'm not sure if there is a simple way to seal one small section without removing the window.


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