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HOW TO REPLACE THE 8 BODY MOUNTS
Here's my "ONE SIDE AT A TIME" procedure for a 77 or any soft
bumper Vette. There are some procedures out there for jacking up the
entire body all at once. This one does one side at a time. I think it is
superior unless you plan to do more than body mount replacement. If
you plan to clean and paint the frame, this procedure doesn't give you a lot
of room to access some areas.
Summary
In a nutshell, you want to remove the bolts from the rear bumper
reinforcement, loosen the 4 mounts on one side, remove the mounts on the
opposite side then repeat for the other side. You need to remove the bolts
holding the body support in the front from the side where the 4 mounts are
being replaced but leave a bolt on the opposite side to keep it from
dropping too much. You are only going to lift each side about 3-4 inches
using 1 hydraulic jack. I used a 2-3 foot 2x4 placed against the frame
under the doors and lifted the body on the metal cage that's available in
this area.
Not Required
No need to disconnect the battery ground strap.
You won't lift the entire body at once. That should help with body to
frame alignment. One side will stay attached maintaining front to rear
alignment.
There is no reason to loosen parking brake adjustment. The
body is not going to be lifted that high. Just make sure the
parking brake is released.
Disassembly
- I put my car up on 4 jack stands so I could access both sides without
removing the rear tire each time.
- Remove the 4 bolts on each rear bumper mount. There are two mounts so 8
bolts come out. Careful. The bottom bolts support the shims. If they are
loose, they might fall out.
- Disconnect the antenna grounding strap.
- Remove the access covers below the A/C and Vapor canister. The bolts
are now accessible to left #1 mount and right #5 mount in front of the
firewall.
- Remove the rocker panels.
- Disconnect the small ground strap found near the #1 mount (front,
drivers side).
- Remove the front grills.
- Remove the front lower panel and spoiler.
- Remove the sill plates and then the kick panels. The bolts to the Left
#2 and Right #6 mount behind the kick panels are now accessible.
- Remove the rear wheels and then the access plates on the front of the
rear wheel well. The bolts are now accessible to left #3 and right #7
behind the doors.
- Remove 2 bolts to loosen the master cylinder from the power brake unit
so the lines won't be stretched when you lift the driver's side.
- Disconnect the steering column from the steering box. You can remove
the steering column from the rag joint by loosening the entire column and
pulling it upward or you can remove the steering box from the rag joint
removing the bolts holding it to the frame. I think the later is probably
easier.
- Disconnect the clutch linkage rod. This will be the rod that goes
through the firewall.
Front Frame Extension Removal
A lot of work to remove these. This was the hardest part of the whole
process because the front bumper cover needs to be removed.
The frame extension is the large piece of flat steel that goes from the
front of the frame horns to the bumpers. There's one on each side. The
frame extension must be removed because it covers one of the two bolts
holding the body support.
- Remove the plastic front bumper cover. Easier said than done. You need
to remove the bumper cover to gain access to the two bolts holding the
bracket. Some bolts are a pain to reach. I gave up and drilled an access
hole in the inner fender to gain access to the stud above the bumper
bracket. You can't see this stud.
- Remove the one bolt holding the corner bumper bracket to the frame
extension.
- Remove 2 bolts on each side holding the frame extension to the frame.
Remove frame extensions.
Mount Replacement
Work on one side at a time.
- Loosen the bolts for body mounts on one side, either 1-4 or 5-8. All
you need to do is break them loose so they wiggle a bit. You don't want
them too loose because they will help keep the body alignment. The 3 rear
mounts on each side have captive nuts. The front mounts on each side have
a standard nut. Hopefully the center 2 mounts won't give you any trouble.
Mine didn't. Not sure what I would have done if they had broken off. The
rear bolt gave me some problems when the bolt head broke from rust.
There's a small cover plate inside the car that holds the captive nut. I
simply drove the broke bolt upward into the car with a punch. It broke the
two rivets holding the cover plate and it simply lifted out. I didn't
bother trying to replace the nut or cover. I used a large washer and
dropped a new bolt in from the top. Better than original.
- Remove the 4 bolts for body mounts on the opposite side.
- Remove 2 bolts on ONE side holding the body support to the frame. One
bolt on each side was hidden by the frame extension bracket removed above.
This will be the side that you want to lift. If you want to support this
side with a second floor jack, place it near the edge that is being
lifted. A good area might be the vacuum tank. There won't be a lot of
weight, especially with bolts on one side helping with support.
- Loosen the bolts on the opposite side, backing them out as much as
possible. What I did was put one of the bolts back in from the frame
extension then removed these bolts and their nuts. The frame extension has
captive nuts. The body support uses separate nuts.
- Place a 2x4 under the cage. I placed it flat against the frame on edge.
The piece I used was about 2' long. I also used a couple of short pieces
under it because my jack didn't have enough lift. If you do this, make
sure they clear the frame as you start lifting. It should be placed in the
area under the door between the two mounts. Make sure it doesn't block
access the two center mounts on each side.
- Slowly lift the side with bolts removed. Make sure nothing is binding.
Make sure the bolts are out the front body support for this side! Also
make sure you've removed all the bolts holding the rear bumper support to
the frame.
- Raise the body just enough to remove the old mounts and place the new
ones on the frame. If you are using a second jack to support the front,
place it off center on the side being raised under the vacuum tank and
lift the front too.
- Drop in new bolts and the other 1/2 of the mount from the top for the
front 3 mounts. The rear mount attaches from the bottom unless you have a
problem like I had.
- Slowly drop the body a little at a time making sure everything aligns
and shims (if any) stay put. Some mounts will touch first. Start to thread
the bolts as soon as possible.
- Make sure the mounts are free to move a bit so you can start the bolts
in the captive nuts and the rubber mounts seat properly.
- My Poly mounts have a sleeve inside. On the first drop, the mount
shifted slightly and the sleeve caught on the body. This prevented the
body from fully dropping.
- Leave the 4 bolts semi-loose. Just snug them against their washers.
- Loosely install the front body support bolts on this side.
- Move to the other side and repeat.
- When you are done, crank down all 8 body mount bolts equally a little
at a time until they are fully tightened.
Finish
- Lift the front to the proper height and tighten the 4
front body support bolts.
- Reinstall the front frame extensions.
- Reinstall and tighten the 8 bolts for the rear bumper
support.
- Reattach the 2 ground straps.
- Reinstall 2 front access panels, 2 rear access panels,
2 rocker panels, and 2 kick panels.
- Reinstall front bumper cover, grills, lower panel, and
spoiler.
- Reattach clutch rod.
- Reattach the steering column to the rag joint.
- Reattach the master cylinder to the power brake unit.
Photos
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