The Stovebolt Site Forums The Shop Area The HiPo Shop Looking for 4.88 gears.. Anyone make them..

I see 4.56's for sale for the 60-72 rear ends. Are they a 8.5" Ring and Pinion set?

What size truck are ya working on? 1/2, 3/4? Those 4.56s are most likely for a 3/4 ton, which is a 10" ring gear. The 8.5 is going to be the later passenger car and '78-'87 truck diff.

1/2 ton

There's 3 different diffs used from '60-'72 on Chevies, the 9 3/8" w/drop out 3rd memeber ('55-'62 style), and 2 variations of the 8 7/8" 12 bolt truck diff. There's not much available for the first one as far as gears, the 3.38 and I think maybe the std 3.90. There's not even a good limited slip for them. As far as the 12 bolt goes, gears are easily available, try Randy's or Precision gear, I think most ratios up into the low 5s are available, though some do requeire a different carrier. Also, if you're looking for a lsd for a 12 bolt, there is a mid year change in '65 from the early 17 spline to the later 30 spline, no lsd being made for the 17 spline. Axle shafts can be swapped, though, to change the spline. Also, with a little machining to shorten and re-groove them, the '71-'72 axles can be used in the '63-'70 housing to convert to 5 lug.

So there is some form of posi in it right now and 3.73's. Are all the truck style rears 12 bolts or were there some 10 bolts?

Couple things I should add. When I bought the truck it already had a 5 lug conversion.

Is there a easy way to tell what everything is in there so I make sure I buy the right parts?

I'm assuming because it is a 5 lug conversion and has a posi in it that it's a later model 30 spline set up. I guess I could tear it all down then order my gears.

Sounds like it may have a '71-'72 axle in it. That axle is more or les a direct bolt in, housing and all. There should be a code stamped on one of the axle tubes that will give the year and original application.
As far as the diffs go, Chevrolet trucks used the truck style 12 bolt from '63-'77, some 4x4s used them later than that, up to maybe '81 or '82. And being a posi doesn't necessarily peg it as a 30 spline, GM did offer a Posi in both styles. But being a 5 lug is a good sign that it's a later unit. A good way to determin if it's truck or car is to look at the wheel bolt circle. Trucks are 5x5, car will be 5x4 3/4.

Bolt patern is a 5x5.. So what do I need to know in order to order a 4.88 ring and pinion? Are the bolt paterns the same for the ring gear to posi unit? How about Dif yoke to pinion gear..