We want to put a 3.42 and posi carrier in our 72. Can somebody tell us what type we need to buy? This is the stock diff. Let me know if I need to get any numbers off of it or anything. Being a 72, is it an 8.5? If it is, do I just need to find a posi carrier for a year range for it? Any help is appreciated. If anybody has these for sale, I would be interested. Mark.
Stock 71-72 axle was the 8.5 10 bolt. It had 28 spline axles stock. Eaton sells brand new posi units. http://store.summitracing.com/partdetail.asp?autofilter=1&part=ETN-19557-010&N=700+0&autoview=sku I built a 71 8.5 10 bolt so that I didn't grenade my 70 8.2 10 bolt. I used 30 spline Moser axles, and of course the 30 spline Eaton Posi. You can probably still find stock posi units in the boneyards. GM used the 8.5 center section up till 1990 or beyond. I think you might need to go 3.55. Not sure they make 3.42 gears for the 8.5.
If the car is strictly for city driving you will be fine. If you plan on any interstate/long haul drives.....go with 3.08
Gee or you can ask me...lol. I am a seller for Randy's also. I can either help you with what part numbers you need or I can get the stuff for you even cheaper than them. Just PM me if you need a quote. You ask in a few threads before this. I also have reconditioned factory posi unit too that will do the job on the street if the money is a little tight. your gear selection for 8.5 is as follows : 2.41 2.56 2 series carrier 2.73 2.93 3.08 3.23 3.42 3.73 3.90 4.10 4.30 4.56 4.88 5.13 5.57 3 series carrier I have rebuild kits posis all types true trac, dura grip, eaton, factory posis wide selection of the gears and even good used gears set when available. Take care and hope to help. Jim
