That should be plenty strong!

Cheers
Greg

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.

This different conversion is meant for highway cruisers with 400 horse and street tires if you’re going to build a monster motor then go 9 inch
Tom

With no intention to rain on Tom's parade here, you might want to look into the Ford Aluminum 8.8 IRS center from an 03/04 Cobra or an '06 - '10 Ford Explorer as an alternative to a 9" Ford. Below is a link to a post I did a while back sharing some information on that particular solution. While not as strong as a 9" they still easily handle 900+ hp in 3400 lb SVT Cobra's. Click here => Ford 8.8 IRS

There is also a very nice HD rear cover available for them from right from FRPP, click here =>Ford Racing IRS Cobra Axle Girdle

When you get done with the conversion the 8.8 IRS center and associated toys will be less expensive than the 9" option. and very likely more than adequate for the application.


Ed

Ed
you’re not raining on my parade you have a perfectly good point I was originally looking for a 8.8 to do this conversion but they are different designs on the 8.9 as far as the front pinion mount. And you have the issue of space it’s kind a close quarters where the Diff goes in the original CSX chassis and looking around when I was trying to find out 8.8 it seems to be easier to find a C3 diff than an 8.8. I just wanted to make something that would bolt directly in without any modifications to the CSX chassis. And if I do find a 8.8 case that will work I will make Kit for that too
And remember I talk to my phone so anything is spelled wrong or doesn’t seem right is the phones fault not mine.
Tom

Tom

Thanks, Tom it was not my intention to. I am flat impressed with what you have done with the C3 hardware.

The 8.8 as you accurately pointed out is physically larger and in the CSX chassis I can easily see where the size will be problematic. If the builder used a less original construction model in the rear of the chassis, like some of the Replica Manufacturers, the 8.8 fit is easier but still requires some fabrication.

Ford's 8.8 IRS is really an alternative to a 9" that requires considerable fitment and fab work. Your approach is a bolt in and I still think a way cool approach.

Ed

{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.


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.



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. **)


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

Robert
All I’m trying to do trying to build something as close to the original and as economical as possible. I’m doing a 427 Chassis ( to help finance my leaf spring car) right now so I set it up so that differential would fit in that of somebody so desires or original Shelby differential . I’m doing one more then I’m switching to 289 Leaf spring. When I put the 9 inch in a 289 chassis I had to modify the chassis to get it in that’s why am using the Corvette All the chassis I’m doing will come with complete original style suspension that would fit a CSX, Kirkam,hi-tech or any chassis that takes original suspension. Except for the first couple of chassis that I did everything else is been as close to original as possible do not know how many I have built Probably more than a bakers dozen
And thank you to everyone that’s posted on this thread I’ve learned more about the C3 Diff since this thread is been posted.
Thank you again to everyone
Tom

Well Tom. I really like your concept and I'm seriously considering it as an upgrade to my car.

But as I look at all the components I have to ask:

What the heck makes the Spicer splined yoke shafts (3-82-268x at $346.00 each) so EXPENSIVE?

The Cobra name, strength low volume?

There are so many Spicer splined yokes available at a third the price.

Just wondering.

Cheers
Greg

I put an 8.8 in my original style chassis from Roger Bollick. It needed a bit of modification to do the install but it fit in fine. I also used the 91 T-bird IRS uprights in the rear and that also needed a bit of modification but I was able to make it fit without too much messing around. Also had to design and build my own control arms to use the Tbird uprights and add new pick up points for the lower arms....

The 8.8 requires a different mount for the front pinion, depending on the year you use. I used a cast iron case, but the aluminum cased units from the year I used were the same for mounting purposes. I welded in a piece of 2 x 3 tubing between the frame tubes, which strengthened the chassis significantly. I had to be sure to weld it eccentric to the frame center so the pinion mounts would line up close to my required pinion angle. Then I cut a half round where the nose would project through. The rear of the differential also needed a modified mounting point, but it wasn't a big deal to fabricate a mount...

Anyway, if anyone is interested I could probably get some pictures. I have found the 8.8 to be plenty strong for my 525 hp 393 engine.

Bob

So I'm still following along on Tom's vision of using a Corvette C3 diff.

But I had to learn more about the Cobra/Spicer half/axle shafts and how they would mate up with the C3 diff.

I found a neat Spicer Parts Catalog on ebay which arrived today and I'm pouring through it learning what I can.

And I think I have a few ideas to work on and suggest to Tom.

Later.

Cheers
Greg

It would be interesting to see a pic of the C3 differential to see if a guy could adapt the Porsche 930 axles to it and the uprights in the same manner that Kirkham does with their diffs now.
I have a couple original style uprights with Corvette spindles in them that would probably work in this situation that I won't be using if anyone would be interested in taking them off my hands for a very reasonable price...

Bob

Bob,PM me.

Cheers
Greg

PM Sent

This concept of using a C3 diff has really got me thinking and also has left me with some questions.

Can any of the experts answer this question for me:

Why did the original 427 Cobra rear suspension use a Spicer splined half shaft?

I would have thought with fixed length upper and lower a-arms the half shaft would be a fixed length also.

Or was it because the original rear suspension used rubber bushings which allowed for a lot of suspension "movement" and therefore required some "slip" action in the half shaft?

Can anyone give a simple explanation?

And if one used fixed a-arm joints (hiems or poly), would a fixed length half shaft like a Corvette C3 half shaft work?

So many questions!

Cheers
Greg

All IRS suspensions used fixed length upper and lower a-arms, Greg. In addition all half shafts are fixed length but usually with a sliding coupling like a drive shaft yolk on the output shaft of a transmission. That I am aware of no IRS has ever been manufactured, for production, with variable length a-arms or half shafts.

As the IRS suspension moves up and down through its range of motion the wheel spindle traces out a modified arc defined by the length and location of the upper and lower a-arms in conjunction with the design engineer's chosen pivot points on the spindle.

As the spindle moves through its range of motion there will be increases and decreases required in the length of the fixed length half shaft to make the connection between the side gears and the axle flange. The changes in required half shaft length are absorbed by either a splined coupling (like used on a drive shaft), usually near the center section, or travel built into the CV joints if the design uses CV joints.

Get yourself one of the free or cheap 3D Cad programs out there, draw up the basic geometry and move it through its range of motion. If you have difficulty visualizing spatial relationships in motion the 3D CAD software will help you see what is going on.


Ed

The original style Cobras use variable length 2 piece half shafts to allow for a change in length as the wheel travels in an arc through the travel of the suspension. These are the Spicer part numbers that I have on my car. Bought them through Amazon:

Spicer 3-3-118KX Slip Yoke
Spicer 3-82-268X Yoke Shaft Assembly
Spicer 3-2-159 Flange Yoke

Hi Ed and Mongoose. Thanks for your responses and info.

How much spline "slip" do you think there is in the Spicer half shaft during the up and down suspension movement?

1/4 to 1/2 and inch?

Cheers
Greg

I never really measured it but if you go by CV joints there is not a lot of movement but there is some. I would expect less than or equal to the slip yoke on a drive shaft. The shorter you make the control arms the greater the impact on the movement.

If you are worried about separation pull out your coil over and move the drive spindle through it's full range of motion measuring the movement of the half shaft. Try to shoot for a similar engagement length as your slip yoke on the transmission tail shaft when you are fully extended and you should be more than safe.


Ed

Hi Tom. I just PM'd you.

Look forward to talking with you.

Cheers
Greg