Been working on this project during my down time at the shop (alot, unfortunately). I have been trying to work on a way to use the stock crossmember bushings to raise the diff. The main reason for doing it this way was because I have a dual mount spring, and I wanted to lower the car more without getting longer spring bolts. Definitely more challenging than just putting a notch in the crossmember.

I actually did notch the crossmember, before changing my mind to do the bushings instead. Here was the notch (1"):



Scrapped that idea since it looks like I will be able to get almost 3/4" with the bushing mods. Hopefully that will give me the stance that Im after, and get the half shafts at a more reasonable angle.
Heres the crossmember mocked up to the frame with the sombrero-looking part of the frame hammered flat:


Heres a modded bushing... The lip is sliced and hammered flat so that it can recess into the crossmember:


Heres where Im at now... This bushing has the tabs that fold over cut off approximately right at the bend to show how recessed the bushing is:


I plan on replicating the tabs on the bottom to attach the bushings to the crossmember, and then I will run the aluminum disks that I had previously.

Any other ideas on how to locate the crossmember without using these bushings (or having a piece of rubber/poly lathe-cut to fit) are welcome

 

So did you use the modified crossmember with the recessed differential? Did it help with the alighment of the half shafts and give the rear better traction through the curves with the car being lowered?

I was planning on recessing the differential in its crossmember and ran across your post here. I thought I would ask before going through all the trouble and not having much if any positive result from it.

Riggs

 

I didnt use the recessed x-member... I have a dual mount spring and I was looking to drop the car a bit more without using longer bolts. If you still have the stock spring mounting location, then the recessed x-member would be the easier way to do this.
My half shafts are level now, but I havent really been able to get the suspension dialed in due to lack of time (and lack of a running car)

I actually scrapped the modded stock bushings in favor of some aluminum ones I machined. (not finished, but you get the idea)


I still have my recessed x-member laying around if you want it... Make me an offer

 

I assume you already know that you should raise your rear static ride height back up to where the inner U's are ~1/2" above the outers to minimize adverse toe-steer in bump/squat, yes?

And, FWIW I've got dimensions and instructions for the old-school method of raising the diff x-member by replacing the bushings with disks (some fab and welding required)...

 

Cut and weld??!! I wouldnt dare modify a corvette permanently
But Id like to see those instructions if you have them handy...

I havent measured the axles, but I know they are at least level to the ground.

 

Would the solid crossmember mount be suitable for street use, Or would it send a lot of vibration into the chassis?

Correcting the half shaft angle is important to me and I would like to make a suitable change to the differential location.


Riggs

 

OK, as mentioned (tho not pictured very well) in the Chevy Power book Corvette Chassis section, these bits would eliminate the rubber bushings - the stepped portions fit snugly into the x-member bores - mount the x-member rigidly to the frame, and should yield ~3/4" to 1" higher diff location in the frame. Once available in anodized aluminum (likely 6061 or other "aircraft" alloy), there's certainly no reason why steel shouldn't work. Best info I have on dimensions is as follows...

Upper rings (functions as spacer in lieu of rubber bushing):
total thickness - 9/16"
thickness of wide section - 7/16"
thickness of narrow section - 1/8"
diameter of wide section - 4"
diameter of narrow section - 3 13/16"
diameter of hole - 2 9/16" (tapering slightly as it goes downward ~2 1/2" - 2 17/32")

Lower plates (secures x-member to frame):
total thickness - 7/8"
thickness of wide section - 7/16"
thickness of narrow section- 7/16"
diameter of wide section - 4 1/4"
diameter of narrow section - 3 13/16"
diameter of hole - 1/2"

Oversimplified instructions: Remove bushings and flatten or cut the tabs off of the x-member. Jack the x-member, w/o bushings, into place against the frame (or to desired height). Insert the rings into the bores snugly around the frame bushing bosses, verify the x-member is where you want it, and tack the rings into place in the x-member (not to the bosses). Lower x-member to complete the welds. Install with plates using appropriate bolts and washers. Of course, as with any such custom fitting, some massaging may be required. And, don't forget that you'll have to re-setup your pinion angle for the height change.

IMCO this mod does not constitute a non-reversible mod, as no changes are made to the frame itself, and spare diff x-members aren't exceedingly rare (have a couple myself).

Yes, this mod might well result in some additional cabin noise, in case you find that sort of thing bothersome. For those less worried about comfort and noise, and who tend to beat on performance machinery you probably ought to consider these (or making your own) while you're at it...

http://www.tomsdifferentials.com/catalog.asp?pg=26

HTH /Charlie