lightweight C2/C3 differential

[Jerry G.]

I just unloaded the race car trailer and moved the spare differential into the shop. These things are HEAVY. Good Grief! Has anyone figured out how to lighten these things for racing? I seem to remember seeing in a later year corvette an aluminum differential. would these work in place of my heavy differential? Jerry

[Duke W.]

Re: lightweight C2/C3 differential

Grand Sports had aluminum carriers. I guess GM cast up a few, but I bet they are hard to find and EXPENSIVE!

But the Grand Sports had a habit of eating ring and pinion sets. Differential coolers helped, but I think the real reason may have been carrier strain that pushed the ring and pinion out of alignment. Plus the carrier has to transmitt all rear suspension loads to the frame.

Aluminum is one-third the density of iron, but it only has one-third the elastic modulus, so in an application were strain is more critical than stress, you might not save much.

At least all that mass is on the rear.

Duke

[Jerry G.]

Re: lightweight C2/C3 differential

I suspect your right on the Grand Sports. It would take a reengineered housing to make it work. I thought the 81 or 82 Vetts had an aluminum differential with an aluminum cross support.

[Gary R.]

Re: lightweight C2/C3 differential

The 80-82 diffs are pretty poor units, the bearing caps are aluminum and that's where they break. I have an 82 diff sitting here but I don't plan on doing much with it. A steel cap can be fit to them to beef them up but they're still no where as good as the 100 lb iron diff's are,even in stock form.The irons can be built to hold up to 1000hp in drag applications.

There's only about 35lb difference between the iron and aluminum not enough to justify swapping them over in my opinion. In fact many guys with 80-82 swap over to irons for a stronger more reliable diff.

IMO the irons are stronger then the C4 Dana's as well. I'd keep what you have especially in a HP car.

Tom's has been working on a billet aluminum diff housing that will allow 12 bolt conversion to all ratios. It's been in developement for the past couple of years but not ready yet.

[Duke W.]

Re: lightweight C2/C3 differential

That was my thought, too. I think the guts of that Corvette aluminum carrier/cross member is Dana 44, which is not as strong as the eariler Corvette-unique cast iron carrier, which isn't that strong to begin with.

Duke

[Gary R.]

Re: lightweight C2/C3 differential

Hi Duke,
Well depending on the year of the iron diff,some were pretty weak, others weren't too bad. Keep in mind most vettes were in the 300-400 hp range but even that range, with abuse, will break them.

With the modifications that Pepe Estranda and Tom Watt developed over the past 40 years the irons are pretty stout in non stock form and appear near stock- outside of the huge inner axle flanges.

[Jerry G.]

Re: lightweight C2/C3 differential

Hi Duke,
Well depending on the year of the iron diff,some were pretty weak, others weren't too bad. Keep in mind most vettes were in the 300-400 hp range but even that range, with abuse, will break them.

With the modifications that Pepe Estranda and Tom Watt developed over the past 40 years the irons are pretty stout in non stock form and appear near stock- outside of the huge inner axle flanges.

I agree, I have road raced my rear differential with an 800HP motor and not had a problem. If prepared properly they hold up. I was hoping that now that i've gone to the Rochester FI motor that puts out considerably less HP I could find a lighter substitute. I hope Tom is succesful. Jerry

[Duke W.]

Re: lightweight C2/C3 differential

I agree, I have road raced my rear differential with an 800HP motor and not had a problem. If prepared properly they hold up. I was hoping that now that i've gone to the Rochester FI motor that puts out considerably less HP I could find a lighter substitute. I hope Tom is succesful. Jerry

It's really torque that beats up transmissions and differentials, not power; however, most gear trains are rated by maximum input torque and maximum input speed, so a 9K rev small block may not overtax the Corvette's transmission or torque capacity, but sustained high revs can shorten bearing life.

Duke