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Mr.8Fifty 02-27-2010 03:07 PM

28 splines
Will the factory 28 spline axles in a 8.5 rear hold up to the punishment of my big block producing about 650hp(flywheel) with MT street radials. Maybe 2 or 3 track visits per year but mainly street.

matt's66 02-27-2010 05:22 PM

If I was to venture a guess, I'd say definately no.

Mr.8Fifty 02-27-2010 05:45 PM

Any ideas about how I can upgrade my rear to 30 spline without using a spool?every posi unit that I look at for my rear only comes in 28 spline

Big Dave 02-27-2010 07:59 PM

You are not looking in the right places. Eaton makes their Positraction diferentials for the 8.5" inch rear is offered in the stock 28 spline and in the 12 bolt sized 30 spline axels. there are others (such as Moser or Strange engieering) that can modify the Eaton to use a 31 spline axel out of a nine inch (which is good because you can not race with a C-clip holding your axels in place regardless of the size or spline count).

Big Dave

jayoldschool 02-27-2010 09:06 PM

Go with the 8.5 rear from the 91-up B body. Big drums, or discs with the 94-96 Impala SS or Caprice police package (option 9C1). Stock 30 spline, lots of ratios available, and proven to hold your power in a 4400lb B body at the strip. Less HP to turn than a 9", too!

Mr.8Fifty 02-27-2010 09:19 PM

what type of modifications to make it work in my 73. Or will it bolt right up?

jayoldschool 02-27-2010 10:16 PM

Not sure if the arm mounts are the same on the 71-76 as the 77 and up. Dave, do you know? The bolt pattern is the same on the axles.

Big Dave 02-28-2010 01:06 AM

1971-'76 uses parallel four link arms with a Panhard bar, the 1977-'98 models used an offset four link without a Panhard bars as the uper two arms that attach to the cast iron housing like a Chevelle rear end are angled in towards the cars centerline. It is about the same size (width) as the earlier rears.

Big Dave

Mr.8Fifty 02-28-2010 01:37 AM

So can I buy a 8.5 30 spline Detroit truetrac and put it my 73 housing and use the Axles from an 91-96 caprice? Or should I just by some moser axles? If so any idea what length?

Big Dave 02-28-2010 09:03 AM

Once you have a 30 spline carrier with your gears installed you can slip in factory forged steel axels or the aftermarket billet axel that is machined out of a different alloy for 20% more strength. Both are the same length.

Big Dave

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