Diff ID #'s

[Peter Ansted]

Just dropped the diff for a complete rebuild. It is from a 63 340 4 speed car and should be a posi unit. The number on the case is 2CA09 2969W. Do I have the correct unit here ? By the way, dropping the diff is the direct result of replacing a leaking seal BEFORE reading the shop manual and learning about such things as backlash and proper pinion seating. Thanks.

[Joe L.]

Re: Diff ID #'s

Peter-----

A "CA" axle code was used for 1963. However, it was used for non-posi (open) differentials with 3.36:1 ratio. Are you sure this car is an original 340 hp?

[Peter Ansted]

Re: Diff ID #'s

Thanks Joe- I am certain this is a 340 car and I believe this is a posi unit - both side yokes turn with the driveshaft yoke. I did find a reference book for diff #'s and it shows a 1970 CAO posi unit available for the 350/350 car. The stamping on the unit is pretty clear. I am wondering if the original diff was replaced by this 1970 unit.

[Kevin Whiteley]

Re: Diff ID #'s

Pete and Joe,

The 68-69 TIM&JG states that the code 2 CAO 9 29 69 W stands for, in this order, 2nd shift, 3.70:1 Posi for SB, built September 29, 69 at Warren. It goes on to say that 69 vehicles produced after Aug 69 used the 70 differential codes, hence the three letter code "CAO", rather than the more common 69 two letter code.

Of course, this is all dependant on the casting number of the differential. If it isn't a 69 number, then the above is moot.

[Peter Ansted]

Re: Diff ID #'s

Kevin - Here are some other numbers off the diff. H 28 9, 3899143 near tail shaft and some design that looks like a sundial, with a pointer at a mark about 1 o'clock. Thanks for your help - some parts for a 70 are not the same as parts for a 63.

[Kevin Whiteley]

Re: Diff ID #'s

The 3899143 is the 67 - 69 casting part number. THe H 28 9 indicates an August 28 1969 cast date. I'm not sure about the "sundial", but I think it may be the approx. time of casting. Definately not a 63 rear end. BTW, this is all book knowledge, I'm not to the point that I could do this by memory

[Joe L.]

Re: Diff ID #'s

Peter-----

The GM #3899143 differential housing casting was used from very late 1966 through 1979. So, it must be the 70 unit that you have here.

[Kevin Whiteley]

Re: Diff ID #'s

Joe, thanks for the correction on the usage of the differential casting. I should have known better, since my book only goes to 69.

[Peter Ansted]

Re: Diff ID #'s

Joe, Kevin - Outstanding ! Thank You !