Hey all
A few weeks ago I was supposed to pick up a rebuilt Differential ...I believe it was from 1972
The man that owns it is in his late 70's and has health problems so I couldnt get in touch with him as he was in the hospital.
Well he called me this morning and I am going to look at it this evening
Does anybody have a comprehensive list of #s so I know what I'm looking at?
He has offered it for $200 and I dont want to miss out on it.
Also, any idea what a set of T Tops with no interior are worth?
I believe he said $100 for the pair
He's not feeling well so I couldnt keep hitting him with questions

Any help with the Diff ID is greatly appreciated

Bob

 

The ratio will be stamped in the bottom by the rear cover. The date code on the LH side. Unless you're looking for a numbers matching housing you're better off looking at the internals. With the cover off look at the posi carrier to check it for cracks from the pin holes to the windows. Look over the gears and see if the bearign caps have the little tabs cast in or are the older straight type. The spiders and clutches changed around 1970-71 The early housing are not as good as the later, the early spiders are not as good as the later ones, and the later clutches are not as good as the early ones. If there are no cracks in the posi then $100-200 is fair. I would not reuse a used differential unless I knew the history but even then I throw out the gears and build from scatch with the best parts.
Gary

 

Thanks Gary
I took a look at it
The story goes... It was rebuilt many years ago and was never used. There is no cover on it (I knew this a month ago when I first talked to him) he said after he got it back from the rebuilder he took the cover off to take a look and the cover is now nowhere to be found.
The house was a dump, the Diff was rusty and I couldnt get it to spin one full rev as I was trying to determine the ratio.
The stamped # on the lower case was AA.... Any idea what the ratio is?

I did pick up a set of T-tops in good shape, all the hardware is there but no Interior, outer chrome is in good shape and at $50 for the pair I couldnt pass them up even if I dont need them.

 

always wondered about this.

can you tell posi vs. non-posi by the outside only?

how many non-posi rears are there, anyway? Is this commonplace or rare?

there's 3 series cases and 4 series, I think 3 for 3.90 ratio and less and 4 for 4.11 and above. how are these differentiated?

Finally, there's small block rears and beefier big block rears. What's the diff between the two, anyway? How can you tell the diff?

for the remanufactured splined yokes that go to the posi case, can they be re-manufactured if the o-ring groove on the case side of the yoke is COMPLETELY worn off? I have a lot of these in my collection!

-85% Jimmy

 

All I can tell you is that when I spun the yoke both of the U-joint carriers spun in the same direction
To me, that defines it as Positraction

Actually I should have bought the thing
Im sure I could get it for less than $100

 

Jeez, Jimmy, you want to know it all.

- can you tell posi vs. non-posi by the outside only?

Only if the case is unmolested. The code on the bottom will allow you to discover its factory specifications. Theoretically, you could hold one axle and turn the pinion. If the axle on the opposite side turns it is either an open diff or a very worn limited slip.

-how many non-posi rears are there, anyway? Is this commonplace or rare?

In total? Who knows. It was the standard rear in Corvettes from '70 on. So you figure there have to be at least a couple hundred thousand if you exclude every rear '69 and back. Does that sound rare? Not to me.

-there's 3 series cases and 4 series, I think 3 for 3.90 ratio and less and 4 for 4.11 and above. how are these differentiated?

The case is the thing the ring gear bolts to. The 4-series case has a thicker flange to move the ring gear closer to the pinion.

-Finally, there's small block rears and beefier big block rears. What's the diff between the two, anyway? How can you tell the diff?

Depends on what year. The only difference in the years that there was a difference is that the high horsepower cars got stub axles with a cap instead of a strap for the u-joint union. But in '72 it went to a one size fits all scheme so there is no difference. It also mattered whether the car was an automatic or a manual. There is no difference in the differential itself. Just the axles.

-for the remanufactured splined yokes that go to the posi case, can they be re-manufactured if the o-ring groove on the case side of the yoke is COMPLETELY worn off? I have a lot of these in my collection!

That I'm not sure of. They do reman the axles to use an insert in the end, but I don't think they do it when there is that much gone.

 

I just hung up with the man that owns it
Im going to pick it up tomorrow for $75

It's got to be worth that much
I saw the recipt for the rebuild which was done in 1978 and half torn to shreads and un readable but I do believe he had the work done
I saw no cracks anywhere in the casting..Inside or out.
I just wish I knew what the ratio was as I have a 3.08 in my car and would like to re- rebuild this one if the gears are a little taller.... or at least have a spare or, something for someone that may need a rear for a cheap price.



As I stated before the code was AA can anybody take a guess as to the ratio ...it is a 1972.

Thanks
Bob

 

Bob,

According to Corvette by the Numbers, '71 to '75 AA = 3.55:1

Paul

 

Thats great!
Now I can have an option between the 3.08:1 and the 3.55:1
I know the unit is worth rebuilding

Thanks again Paul!

 

Nice to have options

 

Yes it is....... especially when you get the parts dirt cheap
I counted my Quadrajets today..... 12 complete and another 5 for parts
Plus the new rear..$75 and a set ot T tops for $50 and a gang of parts left over from when I owned my first C3....

 

According to my tank sticker

3V2VG AA is the 3.08 rear on my 72.

 

SCREW IT!
Anybody interested in a very clean 73?
Its now up for sale

 

Is it worth $75
Theres no cracks anywhere and its complete minus the cover?
Thanks

 

It worth the $75 but I would go through it regardless. If you don't want it I'll drive over and get it. If you want one to build for a backup or different ratio then buy it. Use the best parts to built it too. I have all the parts in New Haven, even a couple of sets of new Tom's 373's. The cost is up there so that's something to consider if this is just a backup.
It's a posi, should have the 4 springs in it. The number of teeth are stamped in the side of the ring gear,just divide them out and you'll know the ratio.
Are you going to the Southbury show on the 17th?

Any questions just let me know.
Gary

 

Thanks Gary
I was figuring it had to be worth $75 as long as the housing is good
I did see the reciept, just couldnt read much of it.
I think Ill grab it
If You want it I can hook up with you at the Southbury Show... Where and what kind of show is it?...Is it the antique show at the training center?
If so is it a swap meet as well?
The guy also has 2 complete doors, power windows for $300.

ps: Im near Danbury

 

AA=3.55 according to my P&A 30B GM parts counter book
AW=3.08
...redvetracr

 

Thanks Redvet
Ill have to check it out a little more closely today.

Hey Doc... is your 72 a 4 speed?
If so do you know how many RPM it turns at either 60 or 70 MPH?
Thanks

*EDIT* Diddint notice it was a Big Block..... Sorry

 

Yes that's the show, they also have a swap meet area. Nice location and show. I don't really need one now, I have 4 complete ones I have to build, but if you don't want it I'll take it. See how it feels when you get another chance to look it over. If the bearings have been sitting since '78 without oil look for rust. It should rotate free and smooth but not loose or snug.
Gary