I am getting a weird vibration which transfers through the whole body while driving. Removed the tightly attached ladder-type skid plate that is called a "catalytic converter guard" by GM.

Vibration gone and H2 is very smooth at all engine speeds. Put it back, and vibration returns.

Has anyone found a way to isolate this skid plate so that it does not vibrate the body? Maybe with some type of rubber insulators?

What the hell is wrong with this thing? It is tight on the frame (torqued to 45ftlb). I did not realize how much vibration it was adding to the vehicle until I took it off.

The reason this came up is that it was originally bent against the exhaust crossover pipe and causing tons of vibration when I bought the used 07 H2. Dealer straightened it out to clear the exhaust by 1/2", & tightened it up. This markedly reduced the vibration, but there is still enough there to make driving with it noticeably more noisy than without.

Anyone find a solution? I would like to keep the OEM (wimpy)protector instead of replacing it with something more costly.

 

i said i'd never help anyone again - dammit, but here goes

it's probably hitting your exhaust pipe, where it crosses over from driver's side to p-side. you have 2 options - put some fender washers between the ucp in the rear to space it away from the frame a bit, or bend it some to clear the exhaust pipe. easiest way i found to bend it is to lay it flat on the driveway, put some 1/4 in plywood under it at each end where it is flat, the drive over it. this will bend it enough to clear the pipe and still fit back on. then you can mash it against some rocks and do it all over again later.

 

Hi Shortbus,

Thanks for the advice. Yes, the UCP (Skid plate) was originally mashed against the exhaust, but the dealer fixed that. So there is now more than1/2" space between the two, with no chance of contact.

But after repairs, the UCP still makes a vibration somehow. Much less than before, but still noticeable.

Something else is wrong. I wonder if body or frame flex could be torquing the UCP and creating the vibration. The UCP bolts are tight. I have no idea how it could be causing a vibration in its current state.

 

try tapping it with a deadblow while you're underneath it, maybe that will give you an idea where it's rattling. did you check the small curved ucp under the transfer case? i've had that cause some rattles when it's been filled with mud. i know you said the rattle went away when you took the cage off, but it's something else to check. when you put the front plate back on, did you make sure those bolts are tight and both the cage and plate are firmly against the frame? i've had those bolts strip everytime the dealership did an oil change - so now i take the ucp off before i go in.

 

I will check all that and report back here!

 

Thanks Shortbus for your help! The transfer case UCP is tight.

Update and summary:

After the dealer fixes the UCP, I still had some vibration. I removed it, and vibration disappeared. I looked at it, and it was still warped.

So I took youradvice and ran over it 17 times with the H2, blocking it with wood bits, and CAREFULLY and slowly almost perfectly straightened it. Took a while to do this, since I had to not only straighten it, but take a warp out of it.

Then I made rubber washers for the back 3 bolts that went between the UCP and body. On the front part, I glued strips of the same 1/8" thick rubber on the last upper half of 4" of the UCP, where it tucks under the front skid plate. Also, I glued similar strips on the upper side of the metal cross pieces with the bolt holes in them.

This way, the entire UCP is isolated against the vehicle frame by the rubber. It worked! Took a 200 mile spin in the H2, with zero vibration. So either the rubber isolators did the trick, or just unwarping the UCP worked. Either way I am really stoked about getting this fixed!

 

Congrats on a relatively easy and almost completely free fix on your Hummer.