Vibration from ladder-type skid plate.

[finall]

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.

[tomp]

does exhaust touch it where it crosses over the ladder? If so, that's your problem. Use large spacer/washers to correct it.

[finall]

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 than 1/2" 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

[iccon]

there is the skid plate the protects the transfer-case this can vibrate as well because it rubs on the case sometimes.
My fix for now was to bend it down out of the way and in the future I am going to bond a urethane pad to it and this will fix the problem.

[timgco]

Originally Posted by finall

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 than 1/2" 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

That 1/2" may not be enough. That part of the exhaust flexes somewhat when you hammer the gas pedal. I've been there!!!!! You could always add some washer to the mounting point closest to your back bumper...if you don;t want to try and bend it more. A 4X4 block of wood and your truck can bend that back for ya.

Also as mentioned there is a small ski back further. If you lay underneith the truck and look under there, you have to look over the top of it. Chances are if your ucp was bashed good, that other skid is too.
You may have to bend it towards the ground. You'll want a couple inches there too.

If that doesn;t do the trick: My question is how f'd is that ucp? If it's really bent up where the front H2 stamped skid plate attaches, it is possible that's where the problem is.

Take some pics...ther are enough of us that have bent the hell out of that stuff under there, the pics should help.

[finall]

Update:

Thanks to a combination of EVERYONEs help I have solved this difficult and persistent problem.

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 the advice 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!

Thanks for everyone's help!

[Adam in CO]

Replace them with the H2O setup.

www.h2ohummers.com