Hi Guys,

I missed this when I looked over and bought my vette. I believe these are the rear body mounts. They are in a little worse shape than the pictures show and I am a bit nervous. Are they hard to replace?
Thanks in Advance for any input

 

Sixx27am,

It depends on whether or not there is underlying damage and whether or not you want to fix it. My body mounts were the same way and there were cracks in the fiberglass pillars as a result. Replacing the caps requires lifting the body off the frame enough to slip the new caps over the pillars. Since my car was off the frame at the time, I cannot tell you how high that is. You will probably have to loosen all eight body mount bolts to lift the car enough. If you search on the forum, you will see that body mount bolt removal is not without risk. I was lucky and didn't damage any of the caged nuts. Also, be aware that when I mated up my new caps, they didn't fit the same way the old ones did, and I had to build up some areas with fiberglass to get them to sit flush. The ottoms of my pillars were not flat either due to pulling against the cage nut after losing support from the cap. Also, the rivet holes didn't line up, which isn't a huge deal if you don't mind drilling new ones. You just hope they're not to close to the old ones.

Yours doesn't look as damaged as mine, but if there is damage under the caps and you want to repair it, I would recommend taking the body off the frame. It's just too difficult to get to everything otherwise. Either way, you are going to have to loosen the body mount bolts. If there is no cracks or damage, you could chose to do nothing and keep an eye on it. Please understand that I'm not trying to scare you off, just giving you a realistic picture. I am on the downside of my resto-mod and that was easily the toughest thing I tackled so far. You don't know what you're going to find when you get those caps off. Here's a couple links to the work I did on mine. Hopefully it will help you in your decision. Mine is one example.

http://www.dans79corvetterestomod.co...rcarriage.html

http://www.dans79corvetterestomod.co...dy-mounts.html

Good luck

MajD

 

What year is your car? Those are the #4 support brackets. They are a challenge to mount new ones especially with the body on or even lifted a little. Originally riveted some have gone to pop rivets or other fasteners. Not sure what your goal is or if you are interested in originality but they should be replaced. Many of the supporting vendors have them. While you are at it you may want to check some of the other underneath support brackets for seat belts and seats




.

RVZIO

 

Thanks for the info guys, I got the car up in the air last night and got a better look, the other mounts and brackets look to be in good shape and the fiberglass under #4 looks ok, not sure what I will find when I replace them though. I am guessing that the #4 mount did not fare so well because it is right behind the rear tires and the car has spent its whole life in the north east.

 

Mine weren't nearly as bad as yours and I decided to do them since I already had the front clip off. The car was completely rust free except for those spots, so I felt like I "had" to. In retrospect, it was probably not the right decision for my car. I spent an extra year and probably $10k doing stuff like this to make the most solid car I could, but now that I'm trying to sell it, all anybody cares about is that it's an automatic with no AC...

Doing these reinforcements is definitely not a weekend job. In theory, it can be done in a couple weekends if you just lift the body off and support it with 2x4's. The problem is that the car is 50-ish years old, so it's very easy to mess up other things in the process (like twisting off body bolts and such). What should be relatively straight-forward can escalate, depending on your particular car. I got lucky with mine, but it could have easily gone sideways. Also, plan for the "while I'm at it" things like new body mount bushings. If you have a tendency to get carried away (guilty!), this will get very involved .

This is one of those jobs there are a dozen ways to approach. If you decide to tackle it, I strongly recommend spending hours reading people's write-ups. I did a thread on mine once it was done to show the steps I took. Things like using weld mounts instead of rivets and feeding the bolt in backward (ignoring the silly caged nut that always gets destroyed) made the job much simpler.

 

While you are deciding what to do for the 'long run", you should seal those mounts off to road-water to keep water out....for the time being. Going to the trouble of replacing them and using Pop-Rivets to hold them would be worse than just leaving them as-is. Pop-Rivets have NO holding power. You need a well-riveted piece to get the strength in it which it needs to retain the body in stressed situations. Your present mounts are much stronger than new mounts with Pop-Rivets.

 

There's a way to do them without lifting the body off. When I did a set, I lifted the car, supported the rear of the body, removed the #4 bolts, cut the frame mounts off( they were rusted too). Then remove the remains of the reinforcements from the body, install the new ones with stainless screws and nuts, put the mount in place as well as the new frame mount and weld it back to the frame. Nothing else is disturbed and you get it done without all the while I'm at it stuff involved in a body removal.

 

Don't even think about trying to unbolt those two big bolts. Get a right angle grinder and cut the heads off. Then a hammer and punch and knock them out from underneath straight up into the back of the car. There is this little sheet metal cage holds the nut in place. There's no way it's going to hold the nut it's going to spin. I would think the body would be able to flex enough to get it up enough to get the bushing out from under drill those rivets and get those reinforcement cages off the body. And new ones in place. If you're going to do that, have the doors open. Convertible or Coupe? Convertibles Flex much easier.

 

Are those replacement mounts? If so, where did you get them. The fit seems very nice. Mine came up about a sixteenth or so short in some ares, and none of the rivet holes lined up with the original holes.

 

Sixx27am, I should've added that there is a tang on those mounts that slips between the rear of the pillar and the splash guard. At the factory, they smeared adhesive on the joints like they were making a peanut butter sandwich, and it's possible that there is a matrix of adhesive, steel, and rust crammed in that narrow gap. You may have to warm that up with a heat gun and use a putty knife to clear that gap so the new mount slides up in there. There is a single rivet hole on that tang, and you may have to grind the head off from the inside to get all the old mount material out. Here is a picture of my new mount so you can see what I'm talking about:


It's the short tang on the right with a single hole in it. The picture below shows where that is. It's the white, powdery spot near the center of the pillar...all that was left of the aluminum. If yours is corroded through, then the tang remains will be easy to get out.

That square shape is the adhesive that had squished between the mount and pillar during production, and why I mention this. Mine was too far gone to be an issue, but I did remove the splash guard to make the repairs and install the new mounts. The head of that rivet is located in the mount well at the rear of the interior, near the speakers.

MajD

 

I believe all of the support mounts came from Zip or Paragon. That was a few years ago!

 

Thanks guys, I've had those parts sitting in the todo pile for a couple of years, now you are daring me to do it. T

For EMURRAY, what are weld mounts?

 

I was just thinking that as I was looking over it last night. Glad to hear someone has tried it with good results.!

 

Great advice thank you!

 

Here is the thread I made. There are pictures in there of the parts with the part number, and how they go in.
https://www.corvetteforum.com/forums...forcement.html
I second the suggestion of cutting the head off and hammering the caged nut out. That's what I did and it worked well.

 

Seems like you are getting good advice and experience from those who have done this. Great that you can do this from under the car. Just take note of all those 'tidbits' of wisdom on how to do this job and get it done well....even though it may not be exactly like it was done in the factory.

 

The following is a post I made on my body off thread that may help you.

Mine is a convertible and may be a little different than a coupe. You won't have to deal with getting the decklid hinges out of the way.

On replacing the #4 body mounts, the biggest problem I had was removing the top outer bolt out of the deck lid hinges. The inner ones I got with a 1/2" ratchet box end wrench. The outers there is no room for it. The heads of the bolts face towards the rear of the car and you can not see them, only reach up inside and feel them. I spent about an hour and a half getting the outer bolt out of the right side hinge with a curved wrench.

When I went to do the left side, I thought to heck with this, and I drilled a 1" hole from underneath through the back of the cavity the hinge is in with a hole saw. I then had my friend run a long extension with a swivel socket, that I taped to stay straight, through the hole and I guided onto the bolt from inside the car. Ten seconds later the bolt was out. I will use a 1" plastic plug to fill the hole and when together, no one will be the wiser.

To remove the #4 body mount I first ground off all the rivets from under the car with a cutoff wheel. I ground into the mount itself a ways to make removal easier.

On the back side of the #4 mount is a panel installed by the factory after the mount was installed. You can not get to the rivet holding that tab to grind it off. I first took a screwdriver and got it up between the panel and the mount tab and pried it to get any bonding agent loose from the mount. I then went back into the cabin of the car and center punched the head of the rivet on the back side. I then took a number 10 drill bit and drilled through the rivet, the mount and the panel behind it. I was then able to free the old mount from all it's rivets. I ground all the remaining rivets flush with the body. I used a punch and drove all but the 2 inside rivets out of the body. I took a 1/2" drill and opened up the back of the panel over the rear tab/rivet where the drill came through after I drilled from the inside. I then took a die grinder and carbide bur and cleaned up the hole to give me good access to the rivet when installing the new one.

The 2 rivets toward inside also have a panel install by the factory over them. I ground the bottom of the body that meets the mount bolt area flat and then put the new mount into position. I then inserted rivets into all the holes except for the 2 under the panel. I used the mount for a template and drilled up through the 2 remaining rivets and up through the panel over them.

My car is not stock in any way, so I was not worried about being NCRS correct with my rivets. I used 3/16 heavy duty rivets and a rivet gun. I first put a bottle jack and a wood block under the mounts and put pressure up against the body to make sure they were seated. I pop riveted everything in place. They are not going anywhere now. They sit square and look good without cutting any panels out of the way. There is only a 1/2" hole at the back of the one panel underneath.

Mike