i have a 1966 chevy c 10 with a 327 powerglide and unknown rear end the numbers on the case are gm10 n 3856525 h285 i and currious as to what ratio these gears have so i know what to swap them out for the reason for the swap is that my truck will do about 65 at 4000 in second
My '65 had "HA" stamped on the rear axle tube. I verified it was a 3.73: 1 gear set by pulling the rear cover, which is the best way to find out what's in it today. The truck is 47 years old, it may not have the original gear set. Or ..... http://www.youtube.com/watch?v=2y9iqvO7RaU I found this on another website... can't vouch for the validity: http://sixty7ss.proboards.com/index.cgi?action=display&board=suspension2&thread=132 REAR AXLE IDENTIFICATION: The production code number contains prefix letters and production date numbers. Axle identification is stamped on the differential carrier along with the date of manufacture. Example: HB 0612 HB = 3.07:1 ratio, O6 = month built (June), 12 = day built(12th) If your rearend came out from under a 66 C10, that tells me its a 1/2 ton truck and there are only three factory gear ratios for a 1/2 ton pickup, 3.07:1, 3.73:1 and 4.11:1. Here are the codes for each one. JQ-4.11:1 HF-3.73:1 These are the only codes my book uses for 66 rearends HA-3.73:1 HG-3.73:1 HB-3.07:1 HH-4.11:1 HC-3.73:1 HQ-3.73:1 HD-4.11:1 Hope this helps!
