Raising the diff with modded bushings

[vette427sbc]

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 of a pain 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

 

[Sam Cogley]

Get some of the Guldstrand aluminum bushings. They're stepped discs that fit into the crossmember, the whole thing is then located by the mounting bolt and the upper disc.

 

[MYBAD79]

Maybe I am overlooking somehing that the brilliant GM engineers had in mind when they designed this ...... ...... .... vibration/noise maybe ??? Once the driveshaft angle is set there does not seem to be a reason for any pivoting of the crossmember so why allow it to pivot ?? The only reason I can can think of is stressing the bolts and the cast iron diff.....
for hat reason I'd stick with a rubber bushing between the frame and the crossmember, I do not believe there's any benefit to go with aluminium or weld it solid.
The diff is connected to the crossmember with 4 grade 8 bolts which are stronger than the cast iron diff that they're screwed into....... so if stress is an issue then the cast stuff breaks before the bolts let go.....

 

[big2bird]

My only input is that you are not raising the diffy. Your lowering the car, by sectioning the frame in that area. The relative position of the diffy to the ground remains unchanged.

 

[phantomjock]

Just curious...
What about the pinion end? Will you fab a new mount there -- or mod the bushings too?
I'm doing a radical raise too - and am planning on a new pinion mount. Meanwhile - I'll keep my eyes on you progress -- keep the pics coming.

Cheers - Jim

 

[Sam Cogley]

Maybe I am overlooking somehing that the brilliant GM engineers had in mind when they designed this ...... ...... .... vibration/noise maybe ??? Once the driveshaft angle is set there does not seem to be a reason for any pivoting of the crossmember so why allow it to pivot ?? The only reason I can can think of is stressing the bolts and the cast iron diff.....
for hat reason I'd stick with a rubber bushing between the frame and the crossmember, I do not believe there's any benefit to go with aluminium or weld it solid.
The diff is connected to the crossmember with 4 grade 8 bolts which are stronger than the cast iron diff that they're screwed into....... so if stress is an issue then the cast stuff breaks before the bolts let go.....

Who knows? Those rubber bushings are incredibly hard, they don't seem to have any "give" for cutting down on vibration or noise. Everyone I've talked to (including myself) hasn't noticed any negative effects from the solid Guldstrand replacements.

 

[vette427sbc]

My only input is that you are not raising the diffy. Your lowering the car, by sectioning the frame in that area. The relative position of the diffy to the ground remains unchanged.

If I wasnt lowering the car in addition to this mod, I would be raising it... I have heard people debate about this before, but say I wasnt lowering the car in addition to this mod. I would be raising the diff, no? the height of the frame is no lower to the ground after the mod. The diff would be higher measuring from the ground after "raising" it.

Just curious...
What about the pinion end? Will you fab a new mount there -- or mod the bushings too?
I'm doing a radical raise too - and am planning on a new pinion mount. Meanwhile - I'll keep my eyes on you progress -- keep the pics coming.

Cheers - Jim

Yeah Im working on the pinion mount. Im still undecided about modding (shaving) the bushings there too or just mod the bracket. The bushing is not 3/4" so I would still have to mod the bracket regardless to make up for the difference.

 

[vette427sbc]

Get some of the Guldstrand aluminum bushings. They're stepped discs that fit into the crossmember, the whole thing is then located by the mounting bolt and the upper disc.

OK... Ive had enough messing with these bushings... Too hard to mod them the way I want.
Are these the stepped discs? I wont have to run bushings with these?
http://guldstrand.com/scripts/prodView.asp?idproduct=122

For $100 that would be worth not dealing with the stock stuff

 

[Sam Cogley]

Get some of the Guldstrand aluminum bushings. They're stepped discs that fit into the crossmember, the whole thing is then located by the mounting bolt and the upper disc.

OK... Ive had enough messing with these bushings... Too hard to mod them the way I want.
Are these the stepped discs? I wont have to run bushings with these?
http://guldstrand.com/scripts/prodView.asp?idproduct=122

For $100 that would be worth not dealing with the stock stuff

Those look like the reinforcements sold by a lot of vendors that work with the stock bushings. You might want to give Guldstrand a call to see if they still have the replacement set.

 

[BBShark]

Get some of the Guldstrand aluminum bushings. They're stepped discs that fit into the crossmember, the whole thing is then located by the mounting bolt and the upper disc.

OK... Ive had enough messing with these bushings... Too hard to mod them the way I want.
Are these the stepped discs? I wont have to run bushings with these?
http://guldstrand.com/scripts/prodView.asp?idproduct=122

For $100 that would be worth not dealing with the stock stuff

Those look like the reinforcements sold by a lot of vendors that work with the stock bushings. You might want to give Guldstrand a call to see if they still have the replacement set.

The link that vette427sbc provided IS to Guldstrand :huh2:

 

[Sam Cogley]

Get some of the Guldstrand aluminum bushings. They're stepped discs that fit into the crossmember, the whole thing is then located by the mounting bolt and the upper disc.

OK... Ive had enough messing with these bushings... Too hard to mod them the way I want.
Are these the stepped discs? I wont have to run bushings with these?
http://guldstrand.com/scripts/prodView.asp?idproduct=122

For $100 that would be worth not dealing with the stock stuff

Those look like the reinforcements sold by a lot of vendors that work with the stock bushings. You might want to give Guldstrand a call to see if they still have the replacement set.

The link that vette427sbc provided IS to Guldstrand :huh2:

Yes, but the product pictured at Guldstrand's link isn't what I was talking about (which are steel, I think, so I apologize for the above inaccuracy). It appears to be the typical aluminum discs that reinforce the rubber mounts, rather than the stepped disc/ring setup that completely replaces them. That's why I suggested that he call to see if the bushing replacements are still available. Sometimes you can buy stuff that isn't in online catalogs...

Here are the pictures and dimensions I posted years ago: http://forums.corvetteforum.com/1558564455-post1.html Should be pretty easy to have them replicated if Guldstrand no longer sells them.

 

[MYBAD79]

If you replace the rubber with poly I doubt you gain a whole lot - the rubber is pretty hard and solid once the bolt is tightened, especially with the aluminum disc... If you replace the rubber with aluminum you might as well weld the entire crossmember to the frame.... only problem then is accessing the differential bolts inside the crossmember....

I drilled my crossmember and the frame horns and used long bolts (1/2" I think but it may have been 9/16") ... the rubber cushions were in ok shape and with these bolts and the aluminum discs under the cushion it is rock solid.... I reinforced the frame mounts too - they're very flimsy. If you use aluminum cushions instead of rubber and stock frame mounts then I wouldn't be surprised if the frame mounts that the crossmember bolts too break.....

 

[vette427sbc]

I called up Guldstrand... They dont have them. I guess Im on my own as far as making something. Ill have to ask for a favor from a machinist friend to make me some bushings.
Id prefer to not weld the crossmember to the frame since I imagine it would be a royal PITA to get the diff lined up with the crossmember and then hop in the car and fuss with threading the bolts in. Its not so easy to get to the rear compartment anymore with the Corbeaus either

Any chance you still have those bushings Sam?

 

[Sam Cogley]

I called up Guldstrand... They dont have them. I guess Im on my own as far as making something. Ill have to ask for a favor from a machinist friend to make me some bushings.
Id prefer to not weld the crossmember to the frame since I imagine it would be a royal PITA to get the diff lined up with the crossmember and then hop in the car and fuss with threading the bolts in. Its not so easy to get to the rear compartment anymore with the Corbeaus either

Any chance you still have those bushings Sam?

I do...they're on my car. No noticeable increase in vibration or noise from the diff...Either GM was being paranoid with those rubber bushings or they assembled some diffs so badly that it made a difference.

Everything you should need to get a set cut at a machine shop should be in my old CF post.

 

[Sam Cogley]

Visible on the end of the crossmember, with one of my extra powder coated spring bolt washers under the bolt head.

 

[Stingxray]

Bushings

Ive had a few people ask about these bushings and got me thinking of making mold's. The Urethane X member bushing would be of 95A hardness. I have not seen a similar product on the market. Installation would slightly lower the car (1/2 inch) and front mount might need to be modified . Gauging interest.:yesnod::flag:

As far as front diff. mount. Leave the single rubber or in my case urethane bushing intact. Loosen the 2 bracket to carrier bolts , Pull out front bolt and rotate bracket up till correct u joint angle is met. Mark and re-drill bolt hole in bracket.