Help decoding differential numbers

[Jon R.]

I tried this on the other site without a definitive answer as to what this differential could have out of.

The differential is out of a late '63 convertible but at least the main case is not original to the car.

The numbers on the front of the main case are 3899143. The date code on the side of the front nose of the casing is C 2. On the bottom of the casing is AWW 065 E 1. I did get the following information:

AW= 3.08

W= Warren plant

06= 6th day of year

5= 1975

E= Eaton

1= 1st shift

The rear cover is 3830308 with GM4.

From some goggling, it appears that the rear cover is indeed off of the '63, however, I can not figure out what the main case came out of.

It does appear to be 3.08:1 based on turning the driveshaft input one revolution and counting the turns on the half shaft output.

Ultimately I want to determine what it came out of and how much HP it can handle! Is it possible to get this information?

Thanks in advance for the help!

[Joe L.]

Re: Help decoding differential numbers

I tried this on the other site without a definitive answer as to what this differential could have out of.

The differential is out of a late '63 convertible but at least the main case is not original to the car.

The numbers on the front of the main case are 3899143. The date code on the side of the front nose of the casing is C 2. On the bottom of the casing is AWW 065 E 1. I did get the following information:

AW= 3.08

W= Warren plant

06= 6th day of year

5= 1975

E= Eaton

1= 1st shift

The rear cover is 3830308 with GM4.

From some goggling, it appears that the rear cover is indeed off of the '63, however, I can not figure out what the main case came out of.

It does appear to be 3.08:1 based on turning the driveshaft input one revolution and counting the turns on the half shaft output.

Ultimately I want to determine what it came out of and how much HP it can handle! Is it possible to get this information?

Thanks in advance for the help!

Jon-----


The GM #3899143 carrier case was used for ALL 1967-79 Corvettes. It was not used for ANY other applications.

How much horsepower can it withstand? Well, that's debatable but I suppose we could say that it can withstand as much power as any application for which it was originally used. That includes, of course, L-88 and ZL-1. However, I will say this much: the 1963-79 Corvette carrier assemblies were not particularly stout. In my opinion, they were extremely marginal for some of the high horsepower and torque applications for which they were originally used. They can be "beefed up" but that involves major modifications.

What was your unit originally installed in? I'd say you got it right---a 1975 Corvette with 3.08 differential.

[Jon R.]

Re: Help decoding differential numbers

Joe,

Thanks for the response. That answers my question!

Regards,

Jon

[Jim B.]

Re: Help decoding differential numbers

I agree with Joe's assessment above"

"extremely marginal for some of the high horsepower and torque applications for which they were originally used"

The attached is of my '65 L78 car's left rear carrier chassis mount bracket. I believe the left most set of arrows depicts a factory weld failure and the right set of arrows depicts an actual material tear. In both cases, these failures seem to be explained by rear axle roll during hard acceleration.

[Jon R.]

Re: Help decoding differential numbers

Jim,

Thanks for the response. I thought Joe was writing about the differential itself, not the chassis mount. But, thanks for the heads up, I will check that area on my chassis too!

Regards,

Jon

[Joe L.]

Re: Help decoding differential numbers

Jim,

Thanks for the response. I thought Joe was writing about the differential itself, not the chassis mount. But, thanks for the heads up, I will check that area on my chassis too!

Regards,

Jon

Jon------


I was referring to the differential, itself. However, the "marginality" I spoke of also applies to the differential supporting structure.

[Gary R.]

Re: Help decoding differential numbers

Jon,
What is your application? I can tell you how to build it for up to 1000hp if you are so inclined. The most power put in front of one of my diff's is 975hp at the crank. Obviously there were other mods that needed to be done since these cars were setup for 300-400hp.

Your particular one, 1975, has some issues but then all 63-82 diff's had issues. If that is original inside, and it might not be because it looks like a after market pinion yoke on it, then you have to check the yokes and ring gear bolts. The posi cases and spiders sets are very good, the clutches lousy.

If you pop the cover off and post or email me pictures I can tell you more.

[Jon R.]

Re: Help decoding differential numbers

Gary,

Thanks for the offer, I will take the cover off and snap some pictures tomorrow.

As of now, the engine is a 327 out of a full size car - a 275HP '67 Impala maybe. I plan on replacing it with a 460HP LS3 and a 5 speed. Now would be the time to make any changes to the differential since I have it out for new trailing arms, suspension, disc brakes and some fiberglass repair.

Jon

[Jon R.]

Re: Help decoding differential numbers

Gary,

Attached are the pictures, it appears that the previous rebuilder might have left out some parts!? Not sure what to do next!

If you need other pictures, let me know.

Regards,

Jon

[Gary R.]

Re: Help decoding differential numbers

With the exception of 2 posi springs missing it looks stock. Those look like they were purposely left out too since they typically do not fall out. The housings from 1967 to 1979 are wider, you can see the jog. The 63-66 were straight edged and used now obsolete single steel shims. The wider housings used a single cast shim, that would usually snap when hammering back in.

So 460HP with that diff, all depends on your driving style. When I build a diff I always ask about power, trans, traction, and driving style. Since the 275hp wasn't what you wanted I suspect you will be hammering it some. Will get on it hard while moving or go to track and launch the hard at 3-5k RPM? Will you have sticky tires or will they spin. Running a Tremic 5 speed is ok, stronger then a stock Muncie or ST-10 but a lot of abuse can create some casting cracks.

If that was my car and I wanted a stronger diff at a minimum I would polish and tune the posi, keep those 10-17 spiders, use ARP RG bolts, fit the caps to 001" rock and use socket heads in them, check the axle faces and replace with hardened tip rebuilt ones if needed. That will get you into the 400-450 range for "most" applications.

If you wanted to get the strongest 10 bolt you would have to built what I coined years ago, a super 10. There is a lot to these and there is a resident CF builder who has been copying my name and not building them the same so beware. I am not trying to sell you anything here just offer some advice. If you have access to a Bridgeport, Surface grinder, and lathe you might be able to do it at home. I have coached many around the world on doing these.

One note, it seems the gear mfg are going from 5 cut to 2 cut gears now which will setup differently then what we have been used to.