Budget 10-Bolt

PARTS LISTDESCRIPTION PN SOURCE PRICERearend assembly, 8.5-inch

10-bolt, used N/A Ecology Auto Parts $54.95Eaton heavy-duty

limited-slip differential EAT 19559 Randy's Ring & Pinion

$430.00Yukon ring-and-pinion gearset YG GM8.5-342 Randy's Ring & Pinion

$170.00Set-up kit YK GM8.5HD Randy's Ring & Pinion $87.00Axle

bearing and seal kit AK 1563 Randy's Ring & Pinion $16.00 x2Axleshafts,

30-spline C-clip GM 12398538 Dutchman $235.00Labor: Set up

rearend N/A Moore Automotive $200.00

The Extreme Budget 10-bolt
While the main focus of our buildup is a fairly stout 30-spline 10-bolt, there is always the option of simply freshening a factory-spec assembly, which is still quite durable. Our assembler, Tim Moore, has put together quite a few stockish 8.5 rears for local customers with excellent results, and he has on occasion used a surprisingly high content of used parts. We've already covered the housing needed, but finding a factory Posi-traction diff in a Nova axle is unlikely. However, finding a late second-gen Trans Am or Z28 in the boneyard isn't so tough, and they're nearly guaranteed to have the desired limited-slip diff. Later 8.5 10-bolts found in mid-'80s vehicles usually have the gov-lock-style limited-slip, and these are best avoided as they have a tendency to fragment under heavy power application.

In our local yards, the complete, drum-to-drum passenger car rear axle is only $54.95, and a creative scrounger could probably take out the open diff and drop in the limited-slip from another rear to maintain that price--the big yards don't seem to care as in the end, it's all scrap to them anyway. But even buying the diff separately is still cheap. Tim Moore swears he's set up plenty of used factory gearsets without incident or even noise, owing to the high quality of GM's stuff and the consistency of its tolerances. Throw in a set of fresh bearings and seals, maybe a posi rebuild kit, and you're on your way. Tim also advises that the cross-shaft that mounts the spider gears is a common wear part and is often responsible for reduced clutching of the posi. Dropping in a new one often brings even original clutch packs back to life (though we're hearing they've been discontinued). Obviously, it's up to you to decide which items to replace and which to reuse, but you can mix and match from our price lists to come up with your own recipe.

PARTS LIST

DESCRIPTION PN SOURCE PRICERearend assembly, 8.5-inch

10-bolt, used N/A Ecology Auto Parts $54.95*Limited-slip

differential, used N/A Ecology Auto Parts $43.95*

Ring-and-pinion, used N/A Ecology Auto Parts $46.90*Set-up kit,

new YK GM8.5 Randy's Ring & Pinion $87.00Posi rebuild kit YP

GM8.5-PC-E Randy's Ring & Pinion $110.31Axle bearing and seal kit, new

AK 1563 Randy's Ring & Pinion $16.00 x2Axleshafts, 28-spline, C-clip, used

N/A Ecology Auto Parts $15.95**Car parts; truck part pricing is

different; core charge applies

`SOURCESDutchman Motorsports; Portland, OR; 503/257-6604; dutchmanms.com

Ecology Auto Parts; Santa Fe Springs, CA; 562/921-9974; ecoparts.com