Ring Gear

[Ray C.]

I am installing the correct differential cover on a late 1963 340HP SWC. I was inspecting the inside of the main case and found the following numbers: 2 GM 3783188-9-32 6 63 on the ring gear. My Chevrolet Corvette 1953-1969 Parts and Accessories Catalog list this ring gear for 1965 to 1968 3.55 ratio part number: 3887836 (set). Would 6 63 represent June 63 and be the original gear for A July car. The rear housing has the correct casting number, date code and is stamped for the 3.55 gears.

Thanks Ray

[Joe L.]

Re: Ring Gear

Ray-----

The GM #3887836 was a 1966 REPLACEMENT part number as far as 1965 goes. As you noted, though, it was the SET (the only way that GM ever sold ring and pinion gears). The reason that this SET was only applicable to 65+ is that the 63-64 applications used a different pinion gear spline configuration, so the 65+ SET was not applicable to those years.

However, the RING GEAR component of the 3.55:1 SET used for 65-68 was GM #3783188. This same ring gear was part of the 3.55:1 SET used for 1963-64. That SET was originally known as GM #3822990. Between the two SETS, only the pinion gear was different (and, only due to the spline-end configuration as the gear end was the same).

The "9-32" you found stamped after the part number refers to the ring and pinion tooth count. "9" are the number of teeth on the pinion gear and "32" is the number of teeth on the ring gear.

The "6 63" does refer to the month and year of manufacture.

[Wayne M.]

While you're in there, check drive pinion #'s

Sounds like your 3.55 set is original, so expect "3820899 GM", with (say) "5_63___9_32" (second line); You can see these #'s by looking over the top of the posi case, using a pinpoint flashlight. You'll have to rotate pinion to see all, maybe even stick a finger in to wipe the flat gear end surface. Your pinion companion flange (edge) should read "823". I assume you're putting on the correct "303" rear cover.

[Ray C.]

Re: While you're in there, check drive pinion #'s

Thanks for the responses! Wayne it is a 303 cover and I will check for additional numbers when I get a chance.

Thanks Ray