Quote:
Originally Posted by i82much
I feel like a lot of these decisions you make when building a car are really strongly influenced by what you might already have, what used stuff you can find locally, etc. I mean if i have an 8.5 or 12 bolt in my shed or I find a decent price on craigslist, I'm not dropping 3 grand on a brand new 9 inch or dana 60 if am building a 500 hp car. But if I'm going to buy a brand new rear assembly anyway, I have a hard time seeing why I'd go with anything other than a 9 or a 60.
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Have three '71 & 72 A-body's that are factory 455 HO cars. All have their McKinnon 12 bolt posi's in them. The lightest of the 3 was raced near 50 years ago with a General Kinetics cam, headers, & slicks eventualy into the very high 11's. With very mildly cleaned up heads, it even ran a little quicker. That car ended up breaking a stock axle & did some damage to one 1/4, then it was parked. Since then i have rebuilt the original 12 bolt XVK but when all the bodywork is finally complete it will only be installed for show duty.
On my T-37 Coupe, it's an original M22 car, but I've shelved it's M22 & XUK coded 12 bolt as they a weak point. The substitution is a not that budget friendly M23W backed by a 30 spline Moser axle TruTrac built up HD 8.5 A-body rear. The goal is to get the Coupe down consistently into the mid 12s in PureStock trim . There is a recipe to accomplish that, & I could easily build an upgraded 12 bolt posi up to swap back & forth. Instead am building another 8.5 A-body.. With the parts have on hand, it will mimic one I built earlier & currently is in a low 11 sec GS clone. That was not a $3300 or $3500 expense, right under 2K at the time. Quality parts have gone up some, & so has my labor, more like $2400 today.
Just in blueprinted 28 spline stock axle form, the same 8.5 A-body rear has proved to be very comfortable in a foot braked auto A-body in the high 11 second range, have built way too many that lived there for many many years. In the early years, nearly all were assembled with nothing but correctly rebuilt 8.5 S spring carriers, & used 3.42 or 3.73 GM gears. As demand for other ratios took off, & builds with much high torque engines were presented to me, I built with more & more with aftermarket posi carriers & axles & US Gear Torque-line gearsets. It was very disappointing to see US Gear get bought & then their excellent ring & pinion line discontinued.
For axle retention, am a big fan of bolt-in tapered bearing axles, & prefer that method of axle bearing many times over aftermarket axle c-clip axle retention or Moser's new 12bolts with ball bearing axle bearings. For EXTREME usage, running different length tracks in what amounts to a much quicker bracket car (1.40's & quicker 60 ft times) have no problem investing in a properly built beefed up aftermarket 9" Ford rear. In a stock appearing very slick high 10 to 13 sec Pontiac, am not impressed at all in looking up under the rear bumper & seeing a 9" or a 9" & one of those goofy curved aftermarket swaybars. Have about the same feeling when run across a similar slick very collectible Pontiac & it has a 6.0 swapped in it
