Impala P Case Posi case question [Archive] - Impala Tech

: Impala P Case Posi case question


rchilson
06-02-2009, 01:22 PM
I have a posi drop out,I am just not sure what year it is.I bought it off ebay,is it a 64 ?



http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=130289591327

Big Dave
06-02-2009, 03:47 PM
It appears to be a 'Thin' case for a 1963 Impala. If you had the 'Thick" case variety it would have a 63 cast where your single 3 is now. Thick or thin has no bearing upon the strength of the case but was determined by the foundry the poured it (both cast the housings to the same GM specs). The number of screws on your posi housing is the important feature as it tells you if you have right or left hand threads holding the case together. Yours should be the new and improved 10 plate clutch with 10 LH screws holding it together. IF it has only 8 RH screws then your posi has only 8 plates. If your carrier has casting number C-30743 it will hold a 3.08 to a 3.70:1 rear gear. Casting number C-30751 and it holds a 4.11 or a 4.56 (that was as high as the factory offered).

Big Dave

rchilson
06-02-2009, 04:16 PM
This unit is an all GM 4.88 posi. The tooth count is 8-39. The case is an original GM of Canada cast and assembled P case. The housing has a casting number of 3789812. The posi unit is an Arma Steel unit and has a casting number of C-30751. The gears are GM gears. The ring gear has a part number of 3830265 and the pinion gear has a part number of 3830262.

Big Dave
06-02-2009, 06:46 PM
The gears are GM gears. The ring gear has a part number of 3830265 and the pinion gear has a part number of 3830262.


I only mentioned that a 4.56 was as high as the factory installed in the car as an option. You could buy up to a 5.13 as a service part from your service center. Aftermarket had higher that that if you wanted it.

Big Dave