Skid plate vibration

I'm hesitant to post this, because my experience with mobtown is nothing short of great. Their customer service and products can't be beat from what I have experienced, however I need a little advice.

Sunday I installed both mobtown rock sliders, and a full set of 3 belly pans in 1/4 steel, (yes they are heavy, I wouldn't begin to think of installing them alone.). Now when ever idling, or stoped there is a pretty noticeable vibration coming from beneath the truck. The transfer case said sits really close to the exhaust cross over, but I don't think that is it. Of course I leave for work before sun up, and return after dark, so none of that helps trouble shooting. I have a 3" Toytech 2.5 lift installed, and that required a 1" differential drop. When the stock plates came off there were 4 spacers on the stock plates, but only 2 would go back on with the new pans. I'm wondering if that wouldn't play a role. Also the two stock bolts which are supposed to go into the center holes on the front plate are not long enough now. I currently have the holes empty until I can find longer bolts, which is proving to be a PITA. Optumatley they would want a spacer, but the bolts are the larger diameter and the stock spacers are for smaller bolts. I'm wondering If I don't need four spacers to lower the front skid plate front and center.

Has anyone else experienced this, and what did you do to remedy it? Does anyone have any advice on where to look, and also where would one find spacers?

Again I must stress the product is top shelf, I just need a little advice on trouble shooting, even if that advice to suck it up, and get used to it, which I quite frankly don't think is the solution, but

 

Hey Pete,

I'd bet my house it is the transfer case plate touching the exhaust cross over. I say this because it did it on our shop truck. At idle, it would vibrate which was odd. It was like at that specific RPM the exhaust moved more than at other RPM ranges.

I don't recall anyone else ever having this issue and as you can imagine it's hard to make them perfect because the exhaust hangs from rubber hangers.

How I fixed it was I ovaled the holes on the transfer case skid vertically by 1/4" or so and that allowed the plate to slip down, then I bolted it back in place.

 

Thanks Joe, Unfortunatley that was my first guess as well, so at lunch today I went out loosened the four bolts and pried that said all the way down, it seemed to make it worse , which has me wondering about spacers. It's really difficult to isolate the location of the sound in the small windows I've had to listen. You don't think the front dif drop comes into plaY?

 

No, the diff wouldn't vibrate.

When the truck is idling, can you look up into the transfer case skid plate with a flash light and verify the exhaust is not touching anywhere? Maybe put pressure against each plate or sliders until the vibration stops?

 

Great thought. If it turns out to be the transfer plate skid, and thoughts on a fix. While I have your attention, do I need spacers on the middle holes of the front skid. The skid hangs down maybe 1/2 to 3/4 of an inch from the block. The stepped bolts which are supposed to be re-used are a bit to short. If they weren't stepped they'd be fine, but the tread just doesn't reach with the step. I will find different bolts, that's not my point it's more an FYI, and curious if that being a solid connection is important

 

You want that connection and all the skid connections solid. Send me pics of the location of the bolts. I think I have the thread pitch written down.

 

It's the center bolts (front to back) on the front skid. They are the same size as the two up front. You have a two+" recessed well built into the skid to bring it up to block, however in my case there is still a sizable gap. Maybe I missed some thing, or maybe I wasn't supposed to re-use the spacers at the rear of the front skid.

I'll check the bolt size in the morning. Its sitting on my work bench

Thanks again for the prompt aid. It's what sets Mobtown ahead of the rest

Even if you don't send stickers with your stuff

 

If I understand you correctly, no you're not to reuse the spacers that came on the truck. I bet that might be causing the vibrations.

 

Anywhere? I should be so lucky that it's that simple. Seems like that would make the vibration worse as it raise the middle plate, and by connection the leading edge of the transfer case skid, but hey it's two bolts couldn't hurt to try

 

This is what you should have for hardware.

 

Ok so I just went out with a flash light to inspect. I re-used the spacers on the 12mm bolts, so I'll remove those at lunch tomorrow, that should allow the two missing 17 mm bolts to work as it will raise the back end of the front plate as well as the front end of the center plate. Thats the good.

The bad is that you are correct the exhaust cross over is sitting hard to the transfer case skid. I can't see a way to raise the exhaust, and the plate is lowered as far as it will go. That was the hardest one to install, I'm not looking forward to pulling it as those two pinck bolts in the rear were an absolute whore to get a wrench on.

I fear this is karma for my sticker comments

 

I bet it's vibrating against the front post where you are missing bolts and I bet it's also vibrating on the exhaust.

 

I bet you are correct. I SHOULD BE ABLE TO FIX THE PRIOR PRETTY EASILY, the question then becomes how to adjust the exhaust or transfer case. I know I could pull it (nightmares and four letter words are filling my head, as my nickels start to prematurely bleed) and try to further elongate the holes, I just don't see there being enough meat left on the bone to create space.

Joe you seem to work 26 hours a day, perhaps in your abundant spare time you could ponder this, and throw me a thought. I've got a pretty complete wood working shop, sadly these ain't wood

 

PM inbound for idea.

 

I installed my skid plates last night and the sliders the night before. I was getting the same vibration with the exhaust cross over hitting the transfer case skid when in reverse with the brake applied. We initially were able to move the muffler supports, because we got the rattle to quit last night but I hit a bump on the way into work and its back. Not as bad as last night but it's there. I was wondering if that pipe gets hot enough to melt a 3/8 strip of gum rubber or silicon that could be wedged between the pipe and skid. That transfer case skid is a real bitch to install as the directions indicated.

I thought about dropping the skid but that kinda gives a big lip to catch onto something. I think it would be similar to bolting the transmission skid to the outside of the engine skid instead of tucking it inside and making the bottom snag free.

 

Hey Joe

I have the same issue as Citizen Rob, vibration from the exhaust to the transfer case skid in reverse...I'm looking into some material used for older car muffler gaskets to put between the skid and the pipe crossover...Love the skids, they work well (I have hit them many times with rocks and roots on my at home torture track) and the truck still works as advertised...just hate the vibration sound...

Update: 10/14/2017 - I found a super easy solution to the vibration...I took a bottle jack and pushed (Bent) the exhaust bracket just north (towards the engine) of the skid plate up about 1/2", which was enough to ensure the exhaust pipes do not touch the plate, does not harm the exhaust system in any way and is working like a charm (Did it about two (2) weeks ago) and no noise...I am still beating the shit out of the truck and no damage where the plates are...Nice to have bulletproof products...

 

Joe - reviving an old thread here, but your drawing reminds me to ask... installed my full skids yesterday and in the process cross threaded one of the front 17mm bolts. My service department says the bolts are M12x1.50. My tap and die set says that’s the size of the small starter step, but not the main body. Any idea what size tap I’ll need to clean the threads with there?

Thanks!

 

Steve, let me look tomorrow. I can’t recall.

 

Thanks!

 

Why aren't you there now?!? You should be sleeping there