rear crossmember modification
Thread Starter
Melting Slicks
Joined: Feb 2004
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From: largo florida
rear crossmember modification
Ok, I was reading somewhere that taking the bushings out of the rear crossmember and bolting up like that will raise the rear 3/4 of an inch, and supposedly help with the toe problems. Are there any problems with doing it this way? I assume you would need those real big aluminum washers though right? Is there any negatives about doing this? Do vibrations get transfered from the rear to the frame?
Race Director
Joined: Nov 2000
Posts: 11,872
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From: Waterloo ontario Canada
I have read about raising the rearend 3/4 of an inch also in my chassie book but they never said how they did it. I thought about actually cutting the crossmember and relocating the center section. I would like to lower the rear of my car but at the same time keep the 1/2 shafts parallel to the ground.
The part that bothers me is driveshaft angle. I spent alot of time getting it just right and vibration free and what would raising the rearend do to that alignment?
I hope people like Twin turbo chime in.
I am interested in this too.
The bump stops would have to be relocated/removed/alterned to prevent bottoming constantly.
The part that bothers me is driveshaft angle. I spent alot of time getting it just right and vibration free and what would raising the rearend do to that alignment?
I hope people like Twin turbo chime in.
I am interested in this too.
The bump stops would have to be relocated/removed/alterned to prevent bottoming constantly.
Premium Supporting Vendor
Joined: May 2000
Posts: 4,312
Likes: 70
From: Clearwater FL
Lostpatrolman,
If you remove the 2 bushings in the rear crossmember and used the aluminum plates instead, I don't see how the whole differential would be secured. The aluminum plates are just reinforcement plates. I don't see how 2 7/16 cores thread bolts will hold any of that from sliding back and forth. Maybe if you shaved part of the bushing on the bottom of the crossmember to be somewhat flush, that would work but I don't think you'll get the 3/4". Here's a pic
I also agree with Norval that the angle of the driveshaft would be a concern.
If you remove the 2 bushings in the rear crossmember and used the aluminum plates instead, I don't see how the whole differential would be secured. The aluminum plates are just reinforcement plates. I don't see how 2 7/16 cores thread bolts will hold any of that from sliding back and forth. Maybe if you shaved part of the bushing on the bottom of the crossmember to be somewhat flush, that would work but I don't think you'll get the 3/4". Here's a pic
I also agree with Norval that the angle of the driveshaft would be a concern.
Melting Slicks
Joined: May 2002
Posts: 2,508
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From: Wisconsin
Best way to do it is to junk that heavy, worthless stock crossmember and build your own. I've got a pivot at the rear of mine and and can shim the front to change pinion angle if need be. The differential is about a half inch from the fiberglass at the top. That crossmember is insanely heavy. It is ridiculus. Maybe just try to find a way to weld a bracket off that other crossmember right next to the differential one and bolt the differential up there. I don't see how it is even worth it to bother trying to change the mounting of the stock one around because it is so damn heavy it might as well just be thrown out and your time be better spent making a new one.
Thread Starter
Melting Slicks
Joined: Feb 2004
Posts: 2,435
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From: largo florida
I agree about the crossmember being heavy. I was so surprised on heavy it was also. I cant scrap it, my dual mount attaches to it. Im not exactly sure how it supposed to be mounted up, I thought they said to remove the bushing, but am not sure. I figured the diameter of the hole would be the same size as the base of that wierd mount and the crossmember would sit on the frame? That is just speculation though. How difficult would it be to correct the pinion angle?
Last edited by lostpatrolman; Sep 23, 2004 at 11:27 AM.
Advanced
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Here's an article, see page 20 of the pdf. http://www.corvettefaq.com/c3/vip.pdf
Last edited by PigPen; Sep 23, 2004 at 01:02 PM.
Melting Slicks
Joined: Nov 2003
Posts: 2,362
Likes: 1
From: San Antonio TX
Well Lost Patrolman you have to go to the next page down to look at the explanation of what they are doing. Even though it does not say it really. I think it states that you would have to cut that rubber bushing that was originally there down the same amount before the reinstall.
If someone else has any idea please chim in.
The only way I can think that you could do without that rubber bushing would be to not only make a 1/4" steel plate for the bottom but for the top as well and have a piece of thick wall tubing with an inside diameter of 23/32" welded between the two plates for strength when getting it tite. That would lower the assembly by 3/4" and not move. If you do decide to do this please use atleast a grade 8 or 9 bolts because of the sheer aspect of the arrangement. Please read what it says fully as it also describes how to change the shock posistion as well as the snubbers.
If someone else has any idea please chim in.
The only way I can think that you could do without that rubber bushing would be to not only make a 1/4" steel plate for the bottom but for the top as well and have a piece of thick wall tubing with an inside diameter of 23/32" welded between the two plates for strength when getting it tite. That would lower the assembly by 3/4" and not move. If you do decide to do this please use atleast a grade 8 or 9 bolts because of the sheer aspect of the arrangement. Please read what it says fully as it also describes how to change the shock posistion as well as the snubbers.
Last edited by SHAKERATTLEROLL; Sep 23, 2004 at 07:37 PM.
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Melting Slicks
Joined: Jul 2002
Posts: 3,000
Likes: 22
From: Boulder Creek California
schmucker
Please provide some pics of that rear crossmember, I've never heard of anyone doing this before. I can figure out a design myself, but it would be great to see how you've done it. Every little bit of inspiration helps
Thanks,
Chris
Please provide some pics of that rear crossmember, I've never heard of anyone doing this before. I can figure out a design myself, but it would be great to see how you've done it. Every little bit of inspiration helps
Thanks,
Chris
Thread Starter
Melting Slicks
Joined: Feb 2004
Posts: 2,435
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From: largo florida
Liveandletdrive, Try this
http://forums.corvetteforum.com/show...=rear+coilover
http://forums.corvetteforum.com/show...=rear+coilover
Last edited by lostpatrolman; Sep 23, 2004 at 11:48 PM.
Thread Starter
Melting Slicks
Joined: Feb 2004
Posts: 2,435
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From: largo florida
i dont think the dual mount corrects toe problems. It would also be nice to get the rear end up higher so my halfshafts are atleast parallel instead of pointing upward like they are now.
Melting Slicks
Joined: May 2002
Posts: 2,508
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From: Wisconsin
No pinion angle problems that I'm aware of (only drove it ~15 miles). With the pinion bolt flush and the position of the rear mount it makes for the correct pinion angle with no shimming. I just set it up equal but opposite to the transmission.
Race Director
Joined: Jan 2004
Posts: 18,191
Likes: 145
From: Snake handler
I've read that VIP thing and I think you have to weld disks to the crossmember after you've removed the rubber. I think it says to use a very specific size tubing to reinforce the arrangement. Then it grade 8 bolts all the way. I've been working on the geometry of my rear end and also need to get the half shafts down and lower the rear (actually, I'm lowering the whole car this winter...) I was also thinking that this would eliminate the crossmember's tendency to flex on that rubber bushing. It seems like it would be much better to have your rear end fixed to the frame...
Doesn't VanSteel or someone sell a kit for this?
pm
Doesn't VanSteel or someone sell a kit for this?
pm
Thread Starter
Melting Slicks
Joined: Feb 2004
Posts: 2,435
Likes: 0
From: largo florida
Hmm.. The only thing i have seen are these. http://www.vbandp.com/detail.aspx?ID=533
They just install where the 2 bolts usually go. I think they are supposed to help flexing a bit.
They just install where the 2 bolts usually go. I think they are supposed to help flexing a bit.
Melting Slicks
Joined: May 2002
Posts: 2,508
Likes: 0
From: Wisconsin
Originally Posted by lostpatrolman
How high did you raise your rear end over stock?
