I'm going to solid mount the diff in my 82 by making aluminum pucks to replace the rubber/poly bushings. Figured now's the time to raise it too, aiming for somewhere around 1/2". Seems pretty straightforward overall. Clearance above the diff is something I'll have to keep an eye on but 1/2" seems doable.




From what I can tell, raising a batwing diff isn't very common. Van Steel said I'm only the second person to ever ask about it. The only info I can find on raising one of these is Bee Jay installing his 1/2" higher than normal. His car didn't come with a batwing, though, so that's a bit of a different situation.

The aluminum pieces aren't hard to make, just some simple lathe work to replace the bushings:


The front puck will be even simpler, basically an 1/8" thick washer. I'll either make that or see if the hardware store has a washer with the necessary dimensions.

From there I've got 3 options, in order of complexity:

1) Drill the center hole offset in my new "bushings". I like this option because it's very simple. I don't like this option because lateral forces will impart a rotational moment on the off center bushings and I'm concerned they could potentially rotate within the batwing.

2) Make the new "bushings" with a center hole and drill a new hole in the frame mount that's 1/2" higher. I'd need to weld on a doubler plate of sorts to the frame mounts since the new hole will overlap with the existing one but that's easy.

3) Cut off the frame brackets and weld them back on 1/2" higher. Basically what Bee Jay did except I won't be starting with the iron diff crossmember design. This would be the cleanest but the most work.

I'm leaning towards option 2. This is a driver, not a show car, and functionality is more important than how it looks. I believe this path will be just as structurally sound as option 3 with significantly less work.

I'll post updates over the next few weeks as I work through getting this installed.

 

I was under the impression that you could buy solid differential mounts for your C3 on the market today. No sense in redesigning the wheel and making your own pucks. Having a metal lathe is fun but no sense in making work for yourself.

Check with Gary "The" Differential expert on this modification because he might know something that could help you.

 

Everything available is for pre-1980 where the diff is mounted to a chassis crossmember. Chevy changed the design in 1980 to the aluminum batwing which mounts very differently to the frame. The market for this modification in 80-82 cars is pretty small which is why nobody has a product available.

 

Have you tried to cross check your bat-wing parts from the later C4 drive line parts. I have a BB C3 and a SB C4. My C4 has had lots of updates done to it's rear end since i have owned it. I upgraded to Polyurethane bushings and mounts on both Corvettes One after the other. I would start by looking at the similarities between the one you have and the 1984 system. Somewhere, someplace GM will have found another use for the part.

I would be very surprised if GM made your new suspension parts and threw them all away before starting on the C4 design. When I upgraded to polyurethane I was trying to make the handling a bit tighter and it worked well. As I get older, I wish I had used the rubber bushing instead. They ride better and last a long time if not neglected.

 

The C4 batwing definitely has some visual similarities to the late C3 unit, but the bushings are not interchangeable. You piqued my curiosity, though, and I found a set of aluminum bushings for the C4 for $260. At least now I have a reference point to know how much I'll be saving.

 

I'm really interested to see how this works out. I've contemplated doing the same thing, and I'm surprised you were only the second person to ask Van Steel for a solution.

 

If I were going to machine some parts to do what you are thinking of have you considered making them from Delrin? It is so much easier to mill and turn that aluminum is. I use Delrin for the prototyping and then go to aluminum if I am satisfied. The Delrin is hard enough to work in place of a solid metal puck and has enough "give" to soften the ride a tiny bit.

Being able to mill and machine the Delrin easily is a big plus for prototyping. Why re-design a part when someone already makes it? There are so many catalogues like McMaster-Carr who carry a zillion parts designed for a lot of applications.

 

Must be back at least 10 years ago. I wanted to stiffen the chassis as much as possible so I ended up drilling out the rubber bushing then welding thick washers to the outer bushing shell. This didn't raise the difference but both cross member and pinion mount are solid.

Interested to see if your poly bushings seem to add chassis stiffness

 

As some one who has worked with both the C3 and C4 Dana 44's I can say that there are little or no interchangable parts between the two. They look almost the same when you hold the parts but they are not the same. Wile we are at it lets throw in the Viper Dana 44. Yes it also shares no parts with the others. OK well the C4 and Viper do share interchangable Ring Gears.