I have a GM posi unit with GM gears (3.36) that I'm trying to figure what they will fit and what seriers carrier it is. I got it off Ebay and it was supposed to be a 3.55 but you know how that goes. Anyway, the numbers on the carrier are 167 and on the other side EO 30140PMI Any help would be appreciated. It's a 12-bolt ring gear and 30-spline.

What are the gear numbers and dates stamped on the ring and pinion? 3.36 is a 10 bolt 8.2 gear ratio. 12 bolts came in 3.31 or 3.55, later a 3.42 was made available. 3.31 is a better ratio than 3.55 and worth more IMHO.

The ring gear has 12-bolts holding it to the carrier. The numbers on the pinion gear are 17 66 -3853008 11 39 GM The ring gear numbers are 5087 37 10 YM1 11SA USA It looks like a mismatched gear set to me. The ring gear doesn't have GM on it anywhere.

Axle Ratio Tooth Combination
2.56:1 41,16
2.73:1 41,15
3.07:1 43,14
3.08:1 40,13
3.08:1 37,12
3.31:1 43,13
3.36:1 37,11
3.42:1 41,12
3.55:1 39,11
3.73:1 41,11
4.10:1 41,10
4.11:1 37,9


Looks like the 11 39 pinion is correct for a 3.55.

Not sure on the ring gear. Could be a 37 10, or 3.70. How many teeth does it have?

The ring gear has 37 teeth. Richmond makes both ratios. 37-10=3.70 or 37-11=3.36 They listed under Corvette though for '63-'79. Will the Eaton posi work? It's 12-bolt and has 30-splines. The seller says he had two and will check to see if he grabbed the wrong one.