C3 conversion for CSX style chassis

[Tjd]

Currently doing a big black chassis and going to use a C3 Corvette differential it’s Direct bolt in will fit Hi tech, Kirkam,CSX or any chassis built to original specs

[my427cobra]

Looks great. Where do we learn more?

Cheers
Greg

[Tom Kirkham]

Tom,

That looks very clever.
Will it fit into a 289 chassis?

[eschaider]

Very creative Tom.

I'm not that familiar with Corvette IRS hardware. Which year did you source the center from. My unfamiliar memory seems to recall the Corvette center castings having a lot of additional bosses for attachment of or to different parts of the Corvette IRS cradle.

I like how clean you made the adapters for the the rear and front mounting points. Have you experienced any fluid leakage at the rear adapter? If you would share, I'd be interested in how you resolved the oil seal between your fabricated adapter, the case and the rear cover?

Very nice job!


Ed

[my427cobra]

Great idea and creativity. I'm not familiar enough with the C3 either (Eaton? or Dana? iron? or alum?) but what is that dif frear cover? Seems to have a part number on it.

Cheers
Greg

[my427cobra]

By the way. I think I see a saleable product there.

Cheers
Greg

[my427cobra]

OK. I see lots of nice Dana 44 diff rear covers on e-bay.

I need to educate myself.

Cheers
Greg

[eschaider]

Originally Posted by my427cobra

Great idea and creativity. I'm not familiar enough with the C3 either (Eaton? or Dana? iron? or alum?) but what is that dif frear cover? Seems to have a part number on it.

Cheers
Greg

The Corvettes and Vipers used "Vitamin C enriched" Dana 44's, Greg.

BTW you're right, I think that Tom's got a salable product there.


Ed

[LMH]

Originally Posted by my427cobra

OK. I see lots of nice Dana 44 diff rear covers on e-bay.

I need to educate myself.

Cheers
Greg

Just make sure it has the correct level plug in the cover.
Larry

[Tjd]

I have a few questions to answer
1. set up shown is for urethane bushings or if you wish you could have the metal elastic like the originals
2. Yes it will fit a 289 chassis I started in 80 building cobras my original plan was to try to build something that was nice and close to the original yet economical that didn’t quite work out that was really nothing that you could use in the stock form so my first one or two cars with a 9 inch straight axle And mustang upper and lower control arms in the front then switched to tubular control arms full-size Ford spindles. did one chassis with the Corvette IRS with cobra suspension. then went to the 9 inch IRS don’t know why thought it was stronger which it is and never use the Corvette diff again
3. Never had a problem with oil leaks in the C3 Diff. but everyone wanted the 9 inch.
4. Believe the C2 and C3 cast-iron cases use the same mounting the C3 aluminum cases have the front pinion mount cast. Ptrying to find a used alouminum case now to check that.
There are remanufactured C3 differentials with all new parts for $1800 and if you want to get more original Down the road. can take it out and put it in an aluminum Diff from cobra racing or Kirkam.
Remember I talk to my phone any miss spelled words or grammar it’s the phones fault
Tom

[Tom Wells]

Tom,

Aluminum C3 cases may be too weak to withstand much HP. I believe they were used behind automatics from the factory, where the cast iron unit was used behind stick shift transmissions.

A friend's Cobra ate one of the aluminum ones in spectacular fashion while just cruising the interstate and minding his own business. Admittedly it already had some spirited use behind a fairly tame small block plus some track day exercise. He has since switched to the cast iron version.

Just a heads-up.

BTW, your disclaimer about the speech-to-text app gave me a good chuckle.

[Tjd]

Tom
Now that you mention it they have two versions of the aluminum case the pissant for a little Old ladies and the bigger one which is a little better but some people are concerned about weight. And they have their own bat wings and not interchangeable from what I understand
Tom

[moore_rb]

Originally Posted by Tjd

Believe the C2 and C3 cast-iron cases use the same mounting the C3 aluminum cases have the front pinion mount cast. trying to find a used alouminum case now to check that.

Yes, most C2 and early C3 Corvette diff cases (up to 78) are externally very similar- everything bolts up in the same places...

I also agree with Tom Wells that the later-C3 aluminum cases (the "O" cases, as in "Oh my God, what a piece of crap") should be avoided in high HP applications. From the factory, these cases were only used behind smog-era small blocks that barely made 150HP at the rear wheels.

This is very cool work, and would be a great alternative for guys who want a cheaper, stronger, and more readily available alternative to the Jag-style diff...

Corvette Diffs are all over the place, and one other nice thing about them is that they were factory stamped with a code that tells you just about everything that is going on inside the case (gear ratio, and whether it has open spider gears, or a posi/limited slip carrier) You can even tell from the stamped code whether the posi units were originally an Eaton posi (used most often behind small block cars), or the the Warren (Auburn) posi carrier that was most commonly used under big-block Vettes. (there are numerous exceptions to this rule, and there are many 66-67 big-block vettes out there with Eaton diffs, but the vast majority of big block Corvettes were sold between 68 and 71, and 80% of those cars had Warren gear cases and posis)

for penny-pinchers who might want to save a few extra bucks by sourcing their own diff from a junkyard and having it rebuilt, Wilcox Corvette has done a ton of the footwork putting together the list of factory stamp codes that will help you determine which corvette gear cases might be best for your project:


63-67 Corvette gear cases:
1963-1967 Corvette Rear Axle Codes and Ratios | Willcox Corvette, Inc.

68-70:
1968-1970 Corvette Rear Axle Codes and Ratios | Willcox Corvette, Inc.

71=82: (remember: Stay away from the "O"s if you plan to add big HP):
1971-1982 Corvette Rear Axle Codes and Ratios | Willcox Corvette, Inc.


Hope this helps...

[my427cobra]

I'm learning so much here as I shift through all the responses:

Cast iron cases: 1963 to 1975

Aluminum cases: 1976 to 1982

Auburn Posi: 1963 through 1967

Warren Posi : coded with a "W" suffix in 1968 through 1970 otherwise Auburn

So I'm looking at Tom's pictures of his adapter:

He appears to be using a Dana 44 rear cover (with filler plug and breather), bolted to the rear of the adapter.

The adapter appears to be fastened to the diff housing with countersunk fasteners in the Corvette diff bolt pattern.

So you use a Corvette diff gasket on the front side and a Dana 44 gasket on the back side

Am I right so far?

Cheers
Greg

[Tjd]

A picture is worth 1000 words. Maybe not that many you are correct Greg.
Robert thank you for the data on the housings much appreciated this is the first Corvette diff I’ve touched since 1982 I was trying to find some pictures of the one did back then don’t know where they are
Tom

[eschaider]

Tom, I thought the Corvet IRS center sections were Dana 44 derivatives. Are they actually something else or do they come out of that same Dana 44 gene pool?

Ed

[Tjd]

Ed
from what I understand they’re not Dana 44’s but you can modify a case to except a Dana 44 I could be wrong I’m no expert. look at Roberts post he gives a good List and location to identify all C2-C3 diff
I’m doing this for my future leafspring car but if anyone’s interested in a set up to convert a Diff let me know I’m waiting for a waterjet guy to give me pricing and then I can figure out a price.
If anyone’s interested
Tom

[my427cobra]

Tom. What's the part number on your rear cover? It seems unusual in that it has a breather.

Cheers
Greg

[Tjd]

Greg
It’s a modified 44 cover the same one that we used on the shelby diff.
Tom

[MAStuart]

Tom when you did your 9 inch fords. What did you use for your stub axles? Were they cut down stock axles? What did you use for half shafts? Would original cobra half shafts bolt to them? Just wondering because I thought about building one to put in a leaf spring chassis.

Thanks Mark