[Maxthe222]

Hey gang,

I am fully rebuilding the original GM 10-bolt out of my 1981 Y85 Pace Car. It's never been out, or even serviced as it would seem, and has reportedly 29,000 miles on it. The axle seals were totally gone, fluid was pretty bad and the axles were very worn. I bought new Yukon axles, all new seals, had it blasted and powder coated (took good photos of the painted on "G" to try paint back on).

Now, the issue was that the Spider/Carrier gears had some minor nicks and chips in them (see attached), and since the axles were very worn, I took the whole diff out and apart to be fully rebuilt. I spent ages and ages trying to find brand new Spider/Carrier gears for a Corporate 10-bolt Series III 8.5" Limited Slip 3.08 disc brake diff with 28-spline axles, and am absolutely baffled how it's been this hard to get those gears. I called Yukon as they list multiple gears for a GM 10-bolt, and they advise that I needed these gears:

YPKGM8.5-P-28 https://www.yukongear.com/shop/ypkgm...LUNLVZlr1YwhMQ

After 2 months of waiting, I've finally gotten them here in Australia, only to discover that they don't match the factory clutch packs and don't sit nicely in the original diff and carrier. Yukon said over the phone that these do not suit the "Gov-Lock" limited slip differentials, but this is not one of those Chevrolet truck spring actuated ones.

How are there so many options for single pegger open diff gears, but zero options for the limited slip differential carrier gears for a f-body GM 10 bolt? Surely there is another option out there? Can anyone please advise where to get new standard carrier gears for a 2nd gen Firebird limited slip differential?

['ol Pinion head]

in the early years of building 8.5 posi rears, I'd run across spalling (deep pitting) of the teeth on the side gears in about 1 out of 10 S spring posi cores. Early to mid 90's in Pick-n-Pulls, crusher yards, & country yards, I was pulling 3-10 of the #8 or #9 8.5 S spring posi carriers a month. As the years rolled on, typ would run across more of the high ratio (2.41-2.56) #9 carriers than the low ratio #8 carriers. Even with proper rebuilding the #9 carriers, & then using them in building rears in conjunction w ring gear spacers (& 10 hardened SBC head bolt washers), there were times i was so far ahead on the #9 carriers. Thus in Pick-n-Pulls, I'd occasionally just pull the "guts" out of the high ratio carriers & place those small parts in a gutted 8.5 A-body or Nova 8.5 rear. Such excess of the #9 carriers allowed me to catch up with needed good condition posi side gears to replace spalled ones in #8 carriers. On the spider gears for 8.5 S spring posi spider gears, can't remember running out, there is a single track carrier that the spider gear may have a different GM part # but it is the same dimension.

As far as replacement axles go, I've only ordered replacement (sealed axle bearing) Pontiac 8.2 10 bolt axles in the Yukon brand. My bet is the replacement c-clip Yukon 2nd Gen axles youve sourced do not have the correct height pilot on the axle so the pilot area goes through the disc brake rotor & propperly locates the factory cast aluminum wheel. The factory snowflake & turbo wheels are hub centric & need the proper depth pilot area to locate the wheel. Dutchman is the manufacturer that has for years, manufactured a proper replacement axle for the '79-81 disc brake 8.5 rears. The Dutchmans can be purchased in stock 28 spline, or 30 spline to mate with Eaton 30 spline carriers.

To confirm nice used condition factiry disc axles, if no axle chew in the bearing lands, I've always jigged up the prospective axle in a spare housing along w a disc brake caliper bracket & a dial indicator to read off the clean hub mtg area. On used disc axles, if more than .007 runout, not good, that oh so slight 'wobble' can contribute to a slight chirping noise coming from the rear brake pads. Ran across this on a very low mile (under 3000 miles) totally stock 10th Anniversary that a rear wheel had been violently curbed in its early sheltered life. While the damaged wheel had been replaced by the prev owner with an NOS wheel, the axle flange had been tweaked enough to create the slight noise.

Randys.... (Yukon) is in business to sell parts & they have a huge distribution network. By parts for the 8.5 rears, that will mean they are selling new posi carriers (mainly import parts from China). Have been mindful of what aftermarket carriers, gearsets, & bearings that I've sourced the last 20 years. Being you are out of the US, & I'd bet used 8.5 posi rears are at a premium, I'd prob source a new Eaton carrier, & if the axles are like what I prev described, going to need a pair of nice used disc axles or new pair of Dutchmans.

[FrankieT/A]

Tom's Differentials

https://tomsdifferentials.com/

[Maxthe222]

Originally Posted by FrankieT/A

Tom's Differentials

https://tomsdifferentials.com/

Thanks Frankie, sent them an email

[Maxthe222]

Originally Posted by 'ol Pinion head

As far as replacement axles go, I've only ordered replacement (sealed axle bearing) Pontiac 8.2 10 bolt axles in the Yukon brand. My bet is the replacement c-clip Yukon 2nd Gen axles youve sourced do not have the correct height pilot on the axle so the pilot area goes through the disc brake rotor & propperly locates the factory cast aluminum wheel. The factory snowflake & turbo wheels are hub centric & need the proper depth pilot area to locate the wheel. Dutchman is the manufacturer that has for years, manufactured a proper replacement axle for the '79-81 disc brake 8.5 rears. The Dutchmans can be purchased in stock 28 spline, or 30 spline to mate with Eaton 30 spline carriers.

Thanks Pinion, the axles apparently fit pretty good for my 28 spline 8.5", they line up nicely so I don't think I have an issue with these.... yet

if no axle chew in the bearing lands

yep you can see there's a bit of a big ring there, which is why I was advised to replace them

I'd bet used 8.5 posi rears are at a premium, I'd prob source a new Eaton carrier, & if the axles are like what I prev described, going to need a pair of nice used disc axles or new pair of Dutchmans.

I really hope not, the Yukon axles were cheap since I could get them off Rockauto. If I have to go Dutchmans, they will be super expensive and take over a month to get here. Used 8.5's aren't easy to come across, but funnily enough, I have another spare diff out of a Turbo Trans Am here I am going to raid if I am still unable to buy brand new gears.

['ol Pinion head]

The side gears for the 8.5 S spring posi were avail at one time through GM dealer, quite expensive, then they were discontinued, & were never avail in aftermarket form. The new 10/17 spider/side gears Tom's lists are for an aftermarket 8.5 Eaton posi carrier. Tom's wife & daughter still run the company, have bought replacement 12 bolt posi spider/side gear sets from Tom's.

A few years ago a Chinese clone of the 8.5 S spring carrier, marketted as a "Monkey Grip" was brought to the market. Would be interesting to disassemble one & measure & visually compare the side gears & spiders to those out of an OEM 8.5 S spring carrier. There have been times I've seen those cheap 8.5 posi's, avail on closeout, for less than $175. Being a low end Chinese product, am very weary of there being any form of high quality metallurgy & heat treating of the side gears & spiders. For what I've been building with 8.5 rears, just way too much risk to use such a carrier in such performance builds.

[Skip Fix]

They are a little slow to respond but still good folks, good parts and good prices from Tom's.

Dutchman's is the only place I have found that will make an axle with the longer brake pilot for discs. They can do 30 sp;line if you just replace the whole carrier with an Eaton 30 spline.