How to remove body mounts C3?
08-13-2009, 02:44 AM
#2
HOW TO REPLACE THE 8 BODY MOUNTS
Here's a "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
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.
Here's a "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
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.
The following 4 users liked this post by hdpete98:
08-13-2009, 06:36 AM
#4
Drifting
Member Since: Jun 2006
Location: Schaumburg (Chicago) Illinois
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I didn't read the large post provided but I would say to keep in mind that it is possible you will break one of the bolts due to corrosion. If so then you have a big problem. I can't think of why you would want to change then unless they are almost corroded away. If so how would you get the bolt out of the caged nuts. So I don't get it.
08-13-2009, 02:18 PM
#6
I didn't read the large post provided but I would say to keep in mind that it is possible you will break one of the bolts due to corrosion. If so then you have a big problem. I can't think of why you would want to change then unless they are almost corroded away. If so how would you get the bolt out of the caged nuts. So I don't get it.
08-13-2009, 04:29 PM
#7
Team Owner
Member Since: Sep 2006
Location: Westminster Maryland
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Hi HDP98,
BOY!!! Your list is quite a piece of work!
NICE!!!
Regards,
Alan
BOY!!! Your list is quite a piece of work!
NICE!!!
Regards,
Alan
08-13-2009, 05:13 PM
#8
08-13-2009, 05:51 PM
#9
Instructor
Question on mounts
I've got a car in the shop right now that somebody put aluminum mounts in and it seems to me that there is absolutley no benefit to doing and that it will probably lead to placing undue stress on the body. ANy thoughts or comments, maybe something I'm not aware of???
I can't think of a reason that anybody would even make them???
Thanks
I can't think of a reason that anybody would even make them???
Thanks
, if you have body mount issues you probably need suspension bushings, brake/fuel lines etc!
The following users liked this post:
delliot (05-12-2020)
08-14-2009, 12:50 AM
#14
The bushing do bread down, rubber and metal. New bushing make a nice difference in the ride quality of the car. If you have a lot a rust the bolts can break off but if the bushings need replaced you gotta move forward. Just another job to do.
08-14-2009, 08:06 PM
#17
Instructor
08-15-2009, 04:08 PM
#18
My body mount replacement job turned into a full body-off project. I hope yours goes a whole lot better.
08-17-2009, 11:03 PM
#19
Drifting
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Location: Schaumburg (Chicago) Illinois
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I am no expert but the number 2 and 3's have cage nuts. If they are frozen and you break them, don't you have to remove the body to start over? I broke off 2 but I was doing a body off.
08-18-2009, 12:52 AM
#20