[vidguy]

I have this rear in the GTO. It's a 2.93 Posi that works great but I want lower gears.
Is there anything ODDball about this rear as I look to replace the posi unit with, say, a TrueTrac?

['ol Pinion head]

Vast majority of '71 8.5 A-body rears were 2.73 ratio, with 2.56's also avail. Factory installed 3.08's, 3.23, 3.42's are a lot harder to come across in this style r/e. Only 2.93 GM 8.5 gears I've run across were made by GM nearly a dozen years later.

On the posi carrier, many '71 8.5 A-body as well as '71 F-body rears had a cone type 2 pinion Warner Motive unit. Have had close to a dozen of the Warner Motives out of original '71 8.5 rears, typically because the cones had worn, bottomed out. Years ago, I'd replace the worn Warner Motive carriers with rebuilt S spring 8.5 posi carriers, as the S spring carriers were affordable to properly rebuild at the time. One can still buy clutch packs for the S spring posi carriers, but they are from an individual that had them mfg, & are near $200 a set...
James, on your rear, I'd pull the rear cover, & drain the grease, if the posi carrier has an S spring between the clutch stacks, it's typically better deal, carrier resale wise, than the cone type Warner Motive. With your freshly built 413 (impressive), what is behind it? A T400 or manual trans? What are your plans with the '67?

[vidguy]

Thanks OPH. It could be a 2:73.. I might be mixing numbers it's been so long since I had it open... I'm taking it into the shop Wednesday for a new Eaton.
Either way I'll have them give me back what they take out and let ya'll know.

It's a TH400 (rebuilt) for spirited cruiser, Dairy Queen burnouts. Attempt to embarrass the guys that have the store bought F5 Cobras around here... A few track trips in the Spring to see how it runs, tune and smile.

Originally Posted by 'ol Pinion head

Vast majority of '71 8.5 A-body rears were 2.73 ratio, with 2.56's also avail. Factory installed 3.08's, 3.23, 3.42's are a lot harder to come across in this style r/e. Only 2.93 GM 8.5 gears I've run across were made by GM nearly a dozen years later.

On the posi carrier, many '71 8.5 A-body as well as '71 F-body rears had a cone type 2 pinion Warner Motive unit. Have had close to a dozen of the Warner Motives out of original '71 8.5 rears, typically because the cones had worn, bottomed out. Years ago, I'd replace the worn Warner Motive carriers with rebuilt S spring 8.5 posi carriers, as the S spring carriers were affordable to properly rebuild at the time. One can still buy clutch packs for the S spring posi carriers, but they are from an individual that had them mfg, & are near $200 a set...
James, on your rear, I'd pull the rear cover, & drain the grease, if the posi carrier has an S spring between the clutch stacks, it's typically better deal, carrier resale wise, than the cone type Warner Motive. With your freshly built 413 (impressive), what is behind it? A T400 or manual trans? What are your plans with the '67?