I have a 1991 Chevy K1500 short bed pickup. I'm replacing the rear cab
mounts (rubber bushings). I have a Chilton and it looks like a fairly
straight forward job, but I have never replaced cab mounts before.
Does anyone have any tips or suggestions before I do the job that
might make it go smoother ?
I purchased the new cab mounts from the dealer, along with two new cab
mount bolts. The steel brackets that the rear cab mounts are bolted to
have rusted through, (rubber cab mount bushings are falling through
the steel brackets) and I will be putting a 1/4" inch thick steel
plate on the top and bottom of the existing steel brackets.
I purchased two 10.9 class 12 mm bolts that are 1/2 inch longer than
the stock cab mount bolts, in case the stock cab mount bolts are no
longer long enough, since I added 1/2" inch to the stack-up with the
two 1/4" thick plates.
One thing I noticed about the stock cab mount bolts (GM part #
15704266) is that they have what looks like a yellow nylon patch on
about a 1 inch long portion of the threads about 1/2" from the end of
the bolt, which I assume is to prevent back-out of the bolts once
their torqued down.
The very end of the stock cab bolts also have some small grooves
running axially through the first three threads. There are 4 or 5
grooves evenly spaced radially around the bolt. The very end of the
bolt almost looks like it's supposed to clean the threads of the weld
nut on the cab floor, almost like a thread chaser.
If I have to use the longer bolts that I purchased, can I just put
some blue removable loc-tite on the end of the bolt to prevent back-
out ? I also have two 10.9 class split lock washers, along with some
regular round washers, I could use under the heads of the bolts as
The main thing that worries me is that when I go to take the existing
cab mount bolts out, they may be rusted to the weld nut on the cab
floor and either strip or break off the weld nut.
When I go to put the new cab bolts in, I had considered putting some
grease on them to keep the thereads from rusting to the weld nut on
the cab floor, however, that would seem to defeat the purpose of the
nylon patch on the stock bolts, and if I use the new longer bolts that
I purchased, I could not use loc-tite on the threads if I use grease,
although the loc-tite itself could possibly prevent rust.
Depending on which bolts I use, do I have any options for preventing
rust where the bolts thread into the weld nuts on the cab floor ? Do I
need to worry about it ?
The rest of the truck is in great shape, and the funny thing is, the
front cab mounts are almost in perfect condition. I'm not sure why the
rear cab mount brackets rusted through, especially since they are
located further from the road (less salt) than the front cab mounts.
Why do these cab mounts rust through, the metal is fairly thick just
like the frame ? Do the rubber mounts hold in moisture and/or salt ? I
have always tired to keep the salt hosed off the undercarriage in the
winter. There were times I drove through some deep water, but if that
was the problem it did not effect the front cab mounts.
In addition to any feedback you may have on my questions, I would
appreciate any general advice that may make the job go easier and/or
come out better.