rear differential gives it's all

[Jerry G.]

The race car ate a 4:11 rear end. Anybody know of a good shipping container for 63-84 Corvette rear ends, need to send this one to the hospital.

[Mike M.]

Re: rear differential gives it's all

5 gal drywall plastic bucket. you'll have to fab a lid as the pig's nose protrudes above the top of the bucket.mike

[Jerry G.]

Re: rear differential gives it's all

Hi Mike, don't you have to remove the stub axles for it to go in. It seems too wide?? I'm planning to send to Tom's differentials in Idaho unless someone know of anybody closer that really knows how to build racing rear ends. I plan on using carbon fiber clutches and 800# springs in the posi.

[Mike M.]

Re: rear differential gives it's all

sorrty jerry, i was thinking you were dealing with a c-1 differential. haven't ever shipped a c-2/3 pig before. regards,mike

[Jim L.]

Re: rear differential gives it's all

The race car ate a 4:11 rear end.

Geez, Jerry, I see broken bolts and they appear to be ARP style with 12 point heads. Is the bolt failure the cause or a symptom?

Jim

[Joe R.]

Re: rear differential gives it's all

I'm not much of a rear end builder but I can see that those are NOT the correct bolts for the ring gear. They were and is the problem! When those little puppies started running around in the housing, there wuz not enough room.

I thought Tom's wuz in California! Tom may have an outlet or gone and franchised?

JR

[Michael H.]

Re: rear differential gives it's all

I'm not much of a rear end builder but I can see that those are NOT the correct bolts for the ring gear.
JR

Yup, probably too hard. Not enough stretch to maintain torque. Also looks like AN washers under the heads? If so, they would be too soft.
Either way, I would use original bolts for that location. I don't think I've ever seen them fail.

[Jerry G.]

Re: rear differential gives it's all

Good eye. Those were ARP 12 point and SAE hardened washers. They were properly torqued for this specific bolt so they should have been streched properly. But..I'm no expert her and clearly we had failure. I thiink the cause was loss of clamping force, which led to shear of bolts. It's been in the race car for 11 years so I guess I found the limit of the service life on this component . The posi has carbon fiber clutches and 800 pound springs so there is some serious force applied to the ring gear. On ward and upward.

[Mike R.]

Re: rear differential gives it's all

Is this a road race car? If so you don't want any springs in the posi. I doubt that you want carbon clutches either. BTW Toms is down the road from my hanger and he doesn't build differentials anymore but he is still in the parts business. Tom has all kinds of tricks including putting 12bolt posi and gears in the Corvette rearend. He also has the non slotted posi clutch plates. Most of the more exotic mods are aimed at drag racing where launching with slicks places extreme loads on the driveline.

There is a misconception that the springs are what make the posi work. It is actually the gear tooth faces pushing the spider gears outward, compressing the clutch pack. The springs are there for starting on ice but applying the parking brake works as well. The key to making the posi work well is having correct clearances.

ARP makes a ring gear bolt but you should use it without a washer after camphering the hole. You can also use NAS shear bolts. If you use anything other than a stock bolt, be careful to keep the first thread out of the shear plane.

Good eye. Those were ARP 12 point and SAE hardened washers. They were properly torqued for this specific bolt so they should have been streched properly. But..I'm no expert her and clearly we had failure. I thiink the cause was loss of clamping force, which led to shear of bolts. It's been in the race car for 11 years so I guess I found the limit of the service life on this component . The posi has carbon fiber clutches and 800 pound springs so there is some serious force applied to the ring gear. On ward and upward.

[Jerry G.]

Re: rear differential gives it's all

My understanding is that the springs preload the clutch pack to set the breakaway torqure which allows the axles to unlock. The toms that I'm thinking of is in idaho. tomsdifferentials.com It's been afew years since i've had work done there so I'll call first. It is a road race car.

[Mike R.]

Re: rear differential gives it's all

Well that is the Tom's that is down the road...but he stopped doing overhaul work and only sells parts now.

The springs do indeed preload the clutch pack which adds some understeer on corner entry. The less preload the less understeer and the clutches will last longer, although this is not much of an issue. None of the GT-1 Corvettes using the stock diff were using posi springs (in the 80's at least) and I recall that Cheverolet even recommended leaving them out althoug I no longer have the source to look up and confirm this.

I remember Tom asking me if I was going to use the springs. He used the same tone you would use to ask someone if they were gay but did not want to offend them....I am pretty sure he will not recommend using springs...

Call him on Monday.

My understanding is that the springs preload the clutch pack to set the breakaway torqure which allows the axles to unlock. The toms that I'm thinking of is in idaho. tomsdifferentials.com It's been afew years since i've had work done there so I'll call first. It is a road race car.

[Brad H.]

Re: rear differential gives it's all

Jerry,
Try Gary Remadei. I believe he is the BEST IN THE BUSINESS today by far. Everything you guys are discussing Gary does. He emails photos of every stage of the rebuild and does second to none work specializing in performance/race applications. He sort of took over where Tom left off...
Gary's number is 203 776-2813 ext 139. Gary Ramadei Corvette Service
You wont be dissappointed
Brad Hood

[Jerry G.]

Re: rear differential gives it's all

Thanks Brad

[Bob I.]

Re: rear differential gives it's all

If you use Gary, as I did . He can provide a shipping container.


Bob

[Gary R.]

Re: rear differential gives it's all

Hi guys,Brad & Bob.

I'm not going to turn this into one of my tech threads as some may think I'm doing it for my own purposes. I will be glad to answer any questions you have if you contact me.

I will make a couple of points here though. Sounds like someone was pointing you in the direction of a new loaded Eaton posi, not what I'd use in my vettes.
1- I never use fiber clutches, I wouldn't use them in a go-cart let alone a vette. Look at my pictures of them on Digital corvettes and you'll see what I mean.
2- I know Tom Watt and do the 12 bolts builds now as well as what I coined as a super 10 bolt a few years ago. You can find my thread on these jobs on DC as well
3-I never build any Eaton posi for c2- c3 with springs or plates. I machine fit them to work without them and they work better with less wear and no hammering. I believe I'm the only one building them like this. Both Brad & Bobs diff's are setup like this.

Looking at your picture I see it's an early diff with the 2nd design bearing caps and stock bolts, the case is probably wrecked,ARP bolts with washers. I use ARP as well only I do not use washers with them in the vette build. I went over this with ARP a few years ago and they do not recommend the washers. I never use stock cap bolts and fit every cap to my spec's or fit a steel cap.

Anyway if I can help you with any questions just give me a call.