Problem with cab mount bolts.

[Craig]

I just purchased my first GMT400 truck. A 1994 2 door GMC Yukon.

I needed something to kick my feet on due to all the snow around so I bought some nerf bars / side steps. They mount right on the existing cab mounts.

To install them, I needed to remove the bolts that go through and secure the cab mounts. Problem is, one of the bolts broke. It runs through a metal cylinder so I'm unable to even grab it with my narrowest vice grip.

There isn't room to weld on a nut and fit a socket over it to dislodge it, and I'm worried that if I drill it out, I'll ruin the bushing that seats the screw.

If anyone is familiar with this problem, I'd appreciate any help.

 

[Bob L]

The sleeve it is in is part of the rubber body mount. If you remove all the bolts on that side including radiator support and loosen the other side you could jack up the cab and pull the mount down from the body and remove it. Then you should be able to get at the broken bolt. I would heat the nut the bolt goes into if it doesn't turn easily as you will either break it again or damage the nut in the cab.

 

[someotherguy]

All of what Bob said but you may also consider pulling up the carpet in that corner, prying the cover off the pocket where the captive nut is, and spray liberal amounts of PB Blaster all down the exposed threads of the bolt before attempting to remove what's left.

Richard

 

[Bob L]

All of what Bob said but you may also consider pulling up the carpet in that corner, prying the cover off the pocket where the captive nut is, and spray liberal amounts of PB Blaster all down the exposed threads of the bolt before attempting to remove what's left.

If you decide to heat the nut from underneath removing the carpet may be a good idea also. If bolt is broken clean you may even be able to weld a nut on top and backing it out into the cab.

 

[Craig]

The sleeve it is in is part of the rubber body mount. If you remove all the bolts on that side including radiator support and loosen the other side you could jack up the cab and pull the mount down from the body and remove it. Then you should be able to get at the broken bolt. I would heat the nut the bolt goes into if it doesn't turn easily as you will either break it again or damage the nut in the cab.[/QUOTE

Prying the cover off the pocket? Is there a way to access the cab mount from inside the cab or would I just have to cut through the floorboard?

 

[someotherguy]

There is a round cover made of sheetmetal, attached to the floor with a sealant. You simply pry it off. Underneath you'll have a pocket with the nut welded in there that the body mount bolt goes through. What pulling the cover gains you is access to be able to soak the exposed bolt down with penetrating oil to help you get the remains out from underneath.

See the round covers, front left driver and front right passenger footboard areas -

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In this pic I've removed the cab body mount area covers, removed the body mount bolts, and threaded them back in from the top to be used as lift points (as well as the rear bolts for the seat brackets) to pop the cab off the frame using an engine hoist -

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Richard

 

[Craig]

So as a last ditch effort, I tried to oil it up the best I could from the bottom and tried to use and easy out. I got a few spins on it, but my hole was a little off center from how the bolt broke and a side of the bolt failed.

I actually think I got a defective bolt as the truck hasn't seen any salt and the mounts are quite clean.

I'm going to take out the driver side seat and pull back the carpet. I'm thinking the best way to fix this is to drill it out and weld in a new nut. Perhaps over the existing one if there is room. I'll have to see.

I just want to make sure there is a cover to access the top of the cab mount. It is a Yukon so it's not the same as a truck cab. I really don't want to have to chop up the floor boards.

 

[someotherguy]

It's the same as a truck cab from forward of the B pillar, so...

Richard

 

[Craig]

It's the same as a truck cab from forward of the B pillar, so...

Richard

Awesome. Thanks Richard.

 

[Big6ft6]

Here is a video I did on cab bolts, I include some tips on getting broken cab bolts out. Whatever you do don't cut the broken bolt flush with the cab and hope to drill 'it out, won't work (ask me how I know) I show the outcome in the video.

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