1960 Rear End Question

[Pete P.]

I have an early 60 Corvette (Oct 60) and the rear end housing has the vent tube and circular Limited Slip tag under the filler plug. From what I learned from the forum is that this is a Posi carrier. However, I have the following numbers on the center section: P/N 3725899, H297, BB011. I checked the rear wheel rotation when the driveshaft is rotated and the wheels rotate opposite. I have Alan Colvin's "Corvette By the Numbers" book and it doesn't mention this 3725899 part number. Is this a Non-Posi passenger center section? And my big question is, can I simply swap this center section with a Posi unit or will the axles have to be changed, also?

Thanks in advance,
Pete

[Jim D.]

Re: 1960 Rear End Question

Looks like it's a 3.36 non posi from a 1958 pass. car. Swapping in a correct posi is a simple job that requires nothing more than a new gasket and correct fluid.

[Pete P.]

Re: 1960 Rear End Question

Jim - Thank you for the information. I was hoping the swap would be easy since the existing differential case is leaking from the flange gasket and pinion seal.

I incorrectly listed my early 60. It should be Oct 59.

Pete

[Gary B.]

Re: 1960 Rear End Question

... I checked the rear wheel rotation when the driveshaft is rotated and the wheels rotate opposite...

Pete,

Refresh my memory. With a post unit, both wheels will rotate in the same direction when the driveshaft is rotated with the rear wheels off the ground. And with non-posi, the wheels will rotate in opposite directions?

Gary

[Mike M.]

Re: 1960 Rear End Question

if there isn't an embossed large "P" in the area of the casting #, then the differential case wasn't originally a posi case. you'll have to remove the differential to determine if someone added a posi carrier to the non-posi case. mike

[Joe L.]

Re: 1960 Rear End Question

I have an early 60 Corvette (Oct 60) and the rear end housing has the vent tube and circular Limited Slip tag under the filler plug. From what I learned from the forum is that this is a Posi carrier. However, I have the following numbers on the center section: P/N 3725899, H297, BB011. I checked the rear wheel rotation when the driveshaft is rotated and the wheels rotate opposite. I have Alan Colvin's "Corvette By the Numbers" book and it doesn't mention this 3725899 part number. Is this a Non-Posi passenger center section? And my big question is, can I simply swap this center section with a Posi unit or will the axles have to be changed, also?

Thanks in advance,
Pete

Pete------


3725899 is the casting number for open (non-posi) carrier housings used for 1957-62 Corvettes as well as 1957-64 passenger cars.

[Pete P.]

Re: 1960 Rear End Question

Gary - I may be wrong, but I read that if you have the rear wheels off the ground with the transmission in neutral and rotated the driveshaft, the rear wheels will rotate in opposite directions if you have a Non-posi rear end.

Jim, Mike or Joe - Can you confirm.

[Pete P.]

Re: 1960 Rear End Question

Joe - Thank you. I need to read better; Alan Colvin's book (page 437) lists the 3725899 an Open (non-posi) unit for Corvette.

So, I guess my car used to have a posi unit as evidence of the housing with vent tube and someone put the Non-posi unit in.

[Joe L.]

Re: 1960 Rear End Question

Joe - Thank you. I need to read better; Alan Colvin's book (page 437) lists the 3725899 an Open (non-posi) unit for Corvette.

So, I guess my car used to have a posi unit as evidence of the housing with vent tube and someone put the Non-posi unit in.

Paul------


Well, the carrier is definitely not original to the car since it originally resided in a passenger car. Since 57-62 Corvette and 57-64 passenger car carriers are interchangeable such swaps often occurred. For instance, a guy blows up his differential back in the old days, so he goes to the wrecking yard and picks up a unit out of a passenger car to replace it. No 1960 Corvette ever originally used a 3.36:1 rear gear ratio, either, and someone may have wanted to change the rear end to a lower numerical ratio. Of course, you won't know what's actually in there until you get the thing out of the car.

[Pete P.]

Re: 1960 Rear End Question

Joe,

Then, can I just swap this non-posi carrier with a correct posi carrier?

Pete

[Joe L.]

Re: 1960 Rear End Question

Joe,

Then, can I just swap this non-posi carrier with a correct posi carrier?

Pete

Pete------


Yup, no problem.

[Pete P.]

Re: 1960 Rear End Question

Joe -

One last question... Can I use the axles I have?

[Joe L.]

Re: 1960 Rear End Question

Pete------


Yes.

[Wayne L.]

Re: 1960 Rear End Question

Check the length of the axles. Axles for the posi were shorter, but they may have left the posi axles in the car when they took out the posi carrier. I am still looking for that information. I have it somewhere.

[Pete P.]

Re: 1960 Rear End Question

Thank you to everyone for the help. I appreciate it.
Pete