[GT182]

Question seeing I know very little about these 10 bolt rears.

What is stock for the 66 GTOs? 8.5 or 8.2 10 bolt? And if it's the 8.5, are 30 spline axles the norm?

Reason is I changed out the cover on my 10 bolt this past Saturday. Cover off and what to I see but a peg-leg rear. No posi unit like I was told it had. And no, I don't go around spinning my tires... cost too much to keep buying tires. That I learned years ago. LOL

I just found this on eBay and I'm thinking of going with the Dura Grip Posi 3.42 rear package. http://www.ebay.com/itm/Dura-Grip-Po...ht_2433wt_1037 This will save a bit on gas, and more running 255/60R15s. Better for crusing out on the interstate highways too. Will this kit work in my stock 10 bolt rear?

Also changed to Valvoline 85W-140 Limited Slip gear oil. I have it in my 2000 Jeep GC's limited slip rearend and it works great... so far. No more rearend howling when you let off the gas and coast like it did before. I'm thinking they never put the additive in when they changed the gear oil a few years ago.

['ol Pinion head]

The link you put is is to an aftermarket 8.5 posi unit, gears & std bearing set (with no axle bearings or the correct carrier bearings to run a 30 spline 8.5 carrier in a common 8.5 housing designed to accept a 28 spline carrier). I've built with that clone eaton style carrier before, but not sure on what gears are being sold by the Vegas Drivetrain bunch. The 8.5 package will NOT work in your '66's original rear. '66 Pontiac A-bodies as they used a gray iron 8.2 Pontiac 10 bolt.

8.5 A-body rears were not used in Pontiac A-bodys till the '73 models. The particular style that has the correct geometry mounting points & will properly bolt up in a '64-72 Pontiac A-body will be aprox 1/2" wider than the '66 Pontiac A-body rear. Have built nearly three hundred 8.5 A-body posi rears & currently have 27 core 8.5 A-body rears in the racks.

I've used 85W-140 in the small Dana rears in the 4.0 Cherokees I've owned.

[GT182]

'ol P, thanks for the info too. I found out just after I posted it ain't an 8.5 but an 8.2. No big deal. Now If I had the posi rear out of my 79 Formula on hand I'd stick that rearend under the GTO.... I could have rear discs too the easy way. LOL

I did find this tho.... http://www.ebay.com/itm/GM-8-2-10-Bo...ht_2306wt_1037

Seems like a good deal, and better for highway crusing with 255s/60-15s and the 3.55 gears. Should be about a 400rpm drop with the 3.36 gear. I can't get the set right now but at least I know what I'm looking for.

['ol Pinion head]

The 2nd Gen F-body rears won't fit, no cast in upper control arm perches in the 8.5 leaf spring rears. In the 90's & up into the mid 00's, I used to rob the factory S spring posi's out of core rears & 8.5 posi Pick-n-Pull rears to rebuild & use in 8.5 A-body builds. In the early 90's, the GM clutch packs #231127, I had around $56 in a box, nearly EVERY used #8 posi unit needed a box of clutches & then had to be shimmed up properly. Today, it's a different deal, the GM clutches have been long discontinued & the reproduction clutch packs are very expensive. Might as well buy a new Eaton carrier.

Cruising rpm wise, there is not that much of a difference in cruising rpm between a 3.55 & 3.36 gear set. If cruising around is what you are after, a set of 3.08's or 3.23's would be a better fit. You'd need a mid ratio 8.2 carrier & nice used gears, as no new 8.2 Pontiac gears in those ratios. Many years ago when I first had 3.08's in my TransAm along with 255-60R15's on 8" turbo wheels the engine ran around 2200 rpm @ 60 mph. For about 18 months I was able to run 265-60R15's. The extra height help even more on the highway & helped kill a little bottom end. I was going through a pair of 255 Eagle NCT's every 6-8000 miles. Being aprox 27.5" tall on the 8" wheels, the 265's seem to last a lot longer. Today, I doubt there is a 265-60R15 available. 275's are taller yet & can often be a tight fit, esp on the rear of '64 & 65 A-bodys.

[Scarebird]

Originally Posted by 'ol Pinion head

The link you put is is to an aftermarket 8.5 posi unit, gears & std bearing set (with no axle bearings or the correct carrier bearings to run a 30 spline 8.5 carrier in a common 8.5 housing designed to accept a 28 spline carrier). I've built with that clone eaton style carrier before, but not sure on what gears are being sold by the Vegas Drivetrain bunch. The 8.5 package will NOT work in your '66's original rear. '66 Pontiac A-bodies as they used a gray iron 8.2 Pontiac 10 bolt...

That's Randy's Ring and Pinion/Yukon gear - mostly source from China, South Korea or India - whoever is cheapest at the time...

[GT182]

Scarebird, I found this one for my 8.2 rear..... http://www.ebay.com/itm/GM-8-2-10-Bo...ht_2306wt_1037

Would you happen to know where it's made?

Also just the posi unit from the same dealer. http://www.ebay.com/itm/GM-8-2-BOP-1...ht_3192wt_1037

Not sure if it alone can be added to my original 3.55 gear set.

[Scarebird]

no clue - just knew the other one as they are 6 miles as the 747 flies away. I would think OPH would have a better idea; I would honestly look for a 71-72 Skylark or Cutlass and snap up the 8.5" in it. Far superior choice of parts - I did and am running a Detroit TruTrac in my 71.

[66Post]

Gary, if you "ain't got on it before, why get on it now?". Just leave it as an open rear. Probably a 3:23 and easy on the gas.