C3 conversion for CSX style chassis

[Tjd]

Mark
Yes I did cut down the stock axle and used 1340 or 1350 series spicier shafts which are the same as the original Cobra If my memory serves me right.
Putting a 9 inch in 289 chassis you have to relieve the front bulkhead because the 9 inch will be too big not by much as I remember it's not a direct bolt and without cutting.
It will go in but it's tight. I will be using C3 diff in my leaf spring car.
Tom

[MAStuart]

Thanks Tom. I have a Kirkham center section but it need work. When its mounted there is not much room. At one time I posted pictures of it mounted and I did not have the top plate on the tower yet and they are a tight fit. I posted the picture to show why you could not mount a jag unit with a top mount. I also have a jag unit and with some custom make side mounts it would work. Thought of using a 8.8 ford but haven't tried to see if it would fit . Your C3 unit looks good. Do you see any problem with the top mount cantilevered over the top strength wise . I think the bottom front mount will keep the twisting up and down in check.

Your 9 inch ford do you have any idea of how wide it was axle flange to axle flange?

[my427cobra]

Tom: which Corvette C3 stub axles did you use in the C3 differential housing?

Standard duty or heavy duty?

How did you match the u-joints between the C3 stub axles and the Spices half shafts?


Cheers
Greg

[Tjd]

Mark
you’re correct the front pinion mount takes care of the rotational torque and the top piece connecting the two mounting tubes there is no clearance problem in the 289 chassis
As I remember the 9” did have tight clearance on the top because I use the cut down 9” housing which has a greater OD than the C3. Do not remember the width of the 9” it was wider and a ***** to get it in the 289 chassis. I made the notches on the inside of the main rail tubes little longer and deeper. Remember I did this almost 40 years ago!
Greg
Spicer half shaft will Bolt on just like the original Corvette Half shift with the correct
u joint. Do not remember which stub shaft I used.
Tom

[MAStuart]

Thanks Tom for your replies.

[joyridin']

The C3 rear ends were just GM corporate 10 bolt rear ends. If you had a big block, they added bigger axles and an Auburn LSD, but it was still a GM 10-bolt. If you have over about 550 hp, even with the Auburn LSD, they will not hold up. Most Corvette owners with a decent amount of horsepower have done a 12 bolt conversion using the 10 bolt housing. It takes some machine work to get it to work, but now you are set for 1000 hp.

Not a bad deal for a small block, but I doubt I would use it behind some of the big blocks I have seen people on here build.

[my427cobra]

The more I look at Tom's C3 diff concept. the more I am impressed and intrigued.

But the more I look at it the more questions I have from Tom or other experts here:

1) The C3 side yokes (axles) that come out of the C3 diff would use a Spicer 5-1350 u-joint with dimensions of 3.625" wide by 1.187/1,188" dia end caps.

2) The Cobra 427 Spicer half shafts (splined yoke shaft p/n 3-82-268x and slip yoke 3-3-118kx) use Spicer 5-160x u-joints with dimensions of 4.188" wide by 1.188" dia end caps

3) So how do you mate the C3 side yoke to the Spicer half shafts since the sizes of the u-joints (3.625" vs 4.188") are substantially different?

Is there a hybrid u-joint to mate the two?

Cheers
Greg

[moore_rb]

Originally Posted by joyridin'

The C3 rear ends were just GM corporate 10 bolt rear ends. If you had a big block, they added bigger axles and an Auburn LSD, but it was still a GM 10-bolt. If you have over about 550 hp, even with the Auburn LSD, they will not hold up. Most Corvette owners with a decent amount of horsepower have done a 12 bolt conversion using the 10 bolt housing. It takes some machine work to get it to work, but now you are set for 1000 hp.
.

This viewpoint is based mainly on the lazy language used in Internet forums. No C2 or C3 Corvette's rear end was a 10 bolt, nor are any of the parts interchangeable with a 10 bolt.

but since the Corvette's rear diff case was held on with 10 bolts... well, there you go... It's a 10 bolt.

The first C2/C3 diff was offered with the 1963 Corvette. Every single one of them from 63 to 82 used a 8.125 inch ring gear, and a Pinion with a 2.125 inch bearing shaft.

The first Corporate 10-bolt differential was offered in 1970 (7 years later) and used a 7 inch ring gear and a 1.75 inch Pinion bearing shaft.

In reality, the Corvette's rear diff design is slightly similar to the later, stronger 8 inch 10 Bolt diffs, but it can also be said that the Corvette diff (and the later 10 bolts) were effectively a scaled down 12 bolt diff, with a shorter pinion shaft, and a 1/4 inch smaller ring gear.

The ony way you are going to break a well built C2 or C3 cast iron diff is if you are dumping 1000+ lbft of torque through it with 33 inch drag slicks.

on street tires, even 1000HP is going to light the tires (especially on a 2500 pound car) long before any diff pieces start breaking...

[joyridin']

Originally Posted by moore_rb

This viewpoint is based mainly on the lazy language used in Internet forums. No C2 or C3 Corvette's rear end was a 10 bolt, nor are any of the parts interchangeable with a 10 bolt.

but since the Corvette's rear diff case was held on with 10 bolts... well, there you go... It's a 10 bolt.

The first C2/C3 diff was offered with the 1963 Corvette. Every single one of them from 63 to 82 used a 8.125 inch ring gear, and a Pinion with a 2.125 inch bearing shaft.

The first Corporate 10-bolt differential was offered in 1970 (7 years later) and used a 7 inch ring gear and a 1.75 inch Pinion bearing shaft.

In reality, the Corvette's rear diff design is slightly similar to the later, stronger 8 inch 10 Bolt diffs, but it can also be said that the Corvette diff (and the later 10 bolts) were effectively a scaled down 12 bolt diff, with a shorter pinion shaft, and a 1/4 inch smaller ring gear.

The ony way you are going to break a well built C2 or C3 cast iron diff is if you are dumping 1000+ lbft of torque through it with 33 inch drag slicks.

on street tires, even 1000HP is going to light the tires (especially on a 2500 pound car) long before any diff pieces start breaking...

Huh? Yes, they were all 10 bolts, which refers to how many bolts are holding the ring gear on the differential. The rear case is being held on by 8 bolts if I recall.

Do whatever you want, but I have a friend here with a small block Cobra (347 cid) and it is putting out 510 hp and 490 Ft lbs of torque. That is pretty close to the much hailed L88 427 of the late 60's. If I were going to invest a fair amount of money in a totally new rear end in my Cobra with my bored and stroked all aluminum S/O, I would go with something a bit better than a Corvette rear end.

[moore_rb]

Originally Posted by joyridin'

Huh? Yes, they were all 10 bolts, which refers to how many bolts are holding the ring gear on the differential. The rear case is being held on by 8 bolts if I recall.

{sigh} so it's going to become an argument.... Ok, fine, but let's argue from facts, please:

Fact #1: A 63-82 corvette ring gear will NOT bolt onto a Corporate 10-Bolt carrier.

Fact #2: A Corporate 10-Bolt ring gear will NOT bolt onto a 63-82 Corvette carrier

Fact #3: A Corporate 10-Bolt Pinion gear will NOT fit in a Corvette carrier (and will not mesh with a Corvette ring gear (nor vice-versa)

Do I need to continue here? The words "GM 10 Bolt differential" mean a lot more than the number of bolts holding anything together, and the number of bolts holding the ring gear to the carrier is totally and completely irrelevant to how strong the assembled unit is.

To put it in "Ford terms": Is a 351 Cleveland and a 351 Windsor the same engine, just they both displace 351 cubic inches?

A 10-bolt is not a 10-Bolt, is not a 10-Bolt...There are at least 3 different GM corporate 10 bolt diff designs... and I repeat again: NONE of them came in Corvettes.

Joyridin- My beef's not with you (none of this is personal). My beef is with misinformation; and your assertion that "all Corvette's used 10-Bolt rears" could be easily misinterpreted by someone (like the 90% of dingaling Corvette owners out there) who don't know all the facts, and the "10 bolt" observation might lead them to think that Corvette differentials suffer from the same stigma as the weaker, 7 inch GM 10 bolts (false) or that the Corvette diff components are interchangeable with trucks or cop cars (also false); and then this falsity gets compounded when you assume that the number of bolts holding the ring gear to the carrier has anything to do with the overall strength of the assembled diff.

Originally Posted by joyridin'

If I were going to invest a fair amount of money in a totally new rear end in my Cobra with my bored and stroked all aluminum S/O, I would go with something a bit better than a Corvette rear end.

So would I; but nowhere in this thread did I (or anyone else for that matter) state that the Corvette diff was the strongest option out there. I did state (and still stand by my statement) that a Corvette diff is going to be MORE than strong enough for the vast majority of Cobra builds (even big blocks), but particularly if one were looking for a strong, capable rear end to put behind a 450-500 HP Windsor. You even stated that your friend's 347 is making L88 caliber power. Well, the Corvette diffs in the late 60's did an ADMIRABLE job of handling the L88's output (unless you can find me a collection of stories out there of L88's blowing their rearends up)... and keep in mind that an L88 Corvette is a larger car, and weighs about 700 pounds more than an average Cobra build.

One reason cast iron Corvette diffs are so easily available today is because they DIDN'T blow up... They outlived the thousands of C2 and C3 cars that rusted away around them over the past 50 years...

If I had the option of spending 1600 on a rebuilt vette center section, versus 2500+ for a beefed-up Jag diff, then I'd be hard pressed to find a legitimate reason to spend the extra $$$ for the Jag piece, ESPECIALLY considering how much easier it is to source a posi carrier for the Corvette diff, versus how much more difficult (and more expensive) it is to find a Jag with Posi.

Originally Posted by my427cobra

A question for Robert (moore_rb):

Isn't the pinion shaft bearing diameter 1.625"?

Cheers
Greg

Yes- You are correct, and I was mistaken. That's what I get for trying to post specs from memory, instead of double-checking my numbers first... Blame my wife- she stopped buying my Ginkgo Biloba supplements a year ago.

Originally Posted by MAStuart

Not a chevy guy so. That did a 65 to 69 Chevelle Camaro Nova ect have for rear ends. I have always been told a 10 or 12 bolt. Does a 10 bolt really have a 7 inch ring gear? How is it measured? Is it the outside Dia ?

late 60's GM musclecars (especially big block cars) came with 12 Bolt diffs (roughly 9 inch ring gear), essentially the same diffs that were used in 1/2 ton trucks of the same vintage)

The first/earliest Corporate 10-bolt diffs (1970-1975-ish) only came in pedestrian passenger cars, and yes: they had a 7 inch ring gears and were not intended for handling large power.

In the later 70's/early 80's. GM began phasing out the 12 Bolt differentials, and began putting a redesigned, beefier, scaled up 10 Bolt diff (first using an 8-1/4 inch ring gear, then later upping it to an even better 8-1/2 inch ring gear) into trucks, and heavier V8 passenger cars (like police cruisers, etc.) some lighter cars and smaller 4cyl trucks still got the smaller 7 inch "early style" 10-bolt, so there are some model years out there where the axles are externally swappable from car to car, but what's inside the case might be strong, or it might be garbage. You gotta pull the cover and see what's inside.

Truck guys are usually the ones who get bit by this the most often, when some guy replaces the 8 inch 10-bolt axle with a 7 inch 10-Bolt from an S10, and figures that because it bolted right in, it must be the right axle.

Then he goes out 4-wheeling and ends up getting towed home with the rear end grinding, clicking, or totally locked up from all the broken pieces inside....


At this point, I've pretty reached my "Peace Out" moment with this conversation...

Tom, I still think your work is a great idea, and is a great alternative to sourcing an expensive, beefed up Jag center section.

Ed Schaider- As always- your contributions to this discussion are thoughtful and well-informed, especially for guys who have to be "Ford guys, using only Ford parts" in their build...

to anyone else, who likes the idea of using Tjd's fancy brackets, and a Corvette diff case in their build, but wants "bigger better stronger" inside that Corvette case, Tom's Differentials (different Tom ) offers a kit for swapping 12-Bolt musclecar internals into a corvette case:

http://tomsdifferentials.com/2011catalog/Pages14-23.pdf

[Tjd]

Greg
Yes there is u-join cross that is two different sizes do not know the numbers but you can look it up referencing the width and the bearing size I know it works because I did it but quite a while ago but there are some guys on this thread that no far more than I do
when I received this C3 case it was the first time I touched one since 1982
Tom

[Tjd]

Greg
U-joint you want 1350 to 1410
It was bugging me so I had to look it up
Tom

[my427cobra]

Thanks Tom. Found it.

Neapco p/n 2-1435 at Denny's Driveshaft.

Cheers
Greg

[my427cobra]

Tom. Are you going to make any more of those adapters?

Cheers
Greg

[Tjd]

Greg
Yes if the demand is there

[Thor maine]

C3 Corvette suspension, a nice 5 or 6 speed all tied to a nice Gm LS motor NOW you have a COBRA replica Kit Car I want to have!!! Long live the Bow Tie in the COBRA!!!

[LMH]

So what’s an average cost to build an installable C3 differential?
Larry

[MAStuart]

Not a chevy guy so. That did a 65 to 69 Chevelle Camaro Nova ect have for rear ends. I have always been told a 10 or 12 bolt. Does a 10 bolt really have a 7 inch ring gear? How is it measured? Is it the outside Dia ?

[Tjd]

Larry
did a quick Google search rebuilt C3 $1600 and if you have a Core knock off 400
So you can figure around two grand or less would give you a rebuild differential with adapter.
working on the price of the adapter right now around 3 to 350 ready to bolt on
Tom

[my427cobra]

Hi Tom. Yes I can imagine there is a lot of machining and welding involved.

Is that 1/4" or 3/8" steel plate for the adapter?

Cheers
Greg