['ol Pinion head]

On the driveshaft, the stock driveshaft will need to be cut 3/4" when the stock 71-72 8.5 rear uses its 3R ujoint yoke. There is a very tough to find 12 bolt 3R yoke that wiil shorten that distance up some, not avail from the aftermarket, though.

On sourcing a suitable core, stay in touch with locals/regionals who buy & part '71 & 72 Cutlasses & Skylarks. The core rears are out there, am still finding them.

[GOAT8U2]

8.5 from a Grand National will also work correct?
Not sure on the axle tube length and where the brakes end up but I'm hoping they're very similar so the wheels don't change their spacing.

I have a GN and I was thinking of getting a Moser for it so I'll pass down the 8 5 to my GTO and build it to 30 spline, hardened 3.90 gears, TA Cover and Tru Trac.

What are 8 2" Nodular, 3.55 rear ends going for us?

[Jay S]

Originally Posted by GOAT8U2

8.5 from a Grand National will also work correct?
Not sure on the axle tube length and where the brakes end up but I'm hoping they're very similar so the wheels don't change their spacing.

I have a GN and I was thinking of getting a Moser for it so I'll pass down the 8 5 to my GTO and build it to 30 spline, hardened 3.90 gears, TA Cover and Tru Trac.

What are 8 2" Nodular, 3.55 rear ends going for us?

Can be done, but not exactly a good fit. The G body is about 3” narrower. The center control arms bolt up, but are in different positions, and makes the pinion angle wrong and the suspension binds up. IRC the spring perches may be in a different position between an A and a G also, G is centered more on the axle. All that is workable, a couple places make control arms to correct the geometry, you can weld on the correct spring perch, and run a 1” wheel spacer to get the tracking closer. I put one in an A body many years ago. Not by any means is it a clean easy swap.

I am going to say $750 decent to $1500 for a nice rebuilt 3.55 8.2 N case.

[JLBIII]

Originally Posted by GOAT8U2

What are 8 2" Nodular, 3.55 rear ends going for us?

Last one I saw for a 1st gen Firebird had a $1500 asking price.

[GOAT8U2]

Thanks Jay for your detailed answer, darn was hoping I'd get lucky there. Sounds like the rears have value and mine have Aerospace disc brakes so that adds way more.

[vicgto]

Originally Posted by 'ol Pinion head

On sourcing a suitable core, stay in touch with locals/regionals who buy & part '71 & 72 Cutlasses & Skylarks. The core rears are out there, am still finding them.

ol Pinion head, you mention 71 & 72 Cutlasses and Skylarks but what about Chevelles, didn't they use 8.5 rear ends in these years?

['ol Pinion head]

Originally Posted by vicgto

ol Pinion head, you mention 71 & 72 Cutlasses and Skylarks but what about Chevelles, didn't they use 8.5 rear ends in these years?

Have yet to run across a factory installed 8.5 A-body rear in a '71 or '72 Malibu, Chevelle, MonteCarlo or ElCamino. From extensive bone-yarding, dragging in partscars, & pulling r/e cores, these lower horse Chevy models continued to receive 8.2 Chevy 10 bolts.

Once the 4 bbl 350 Chevy engine was optioned, a single track 12 bolt Chevy rear was standard. Many years ago, I cked a '72 ElCaminio in a monstrous S Dallas pick-n-pull. It had an 8.5 A-body in it along with a slightly shortened driveshaft (which had been cut down) in the bed. I grabbed both. That was in a Fremont CA built ElCo. Ever since I've cked multiple dozens of late built 72 ElCo's & Malibus when I could still find them intact. Before that moment, I'd easily pulled a dozen 12 bolt cores out '72 ElCo's.

72 production.... GM shifted a lot of ElCamino production to the Fremont assembly plant for the 1972 models. The Fremont GM Assembly plant still built a wide range of GM division A-bodies in '72. Mention that as have also noted, the production of '72 Pontiac A-bodies out of Fremont was very low compared to '71 production. Could some very late built Chevy A bodies or variants received a same ratio (2.73) Buick or Olds built 8.5 A-body rear due to supply on hand isues near the model end of year? The 73's model A-body's would not be able to use them. It would have taken a specific driveshaft. One that was slightly shorter & the driveshaft & the trans yoke was built with 3R ujoint features. That would be no issue if the fitted driveshafts were made in house. If such a rearend usage was factory installed, i would also think there would have been a technical service bulletin issued noting it.

[Verdoro 68]

Just to follow up, I've been feeling some slippage with the 8.2 under power lately which accelerated my hunt for a new rear diff. I came up dry regarding reasonably priced 8.5 or 12 bolt cores locally. What I have found would need a full rebuild, new axles and a ratio change. By the time I'd be done, I'd be in the neighborhood of a Moser setup minus all the perks.

So, I bit the bullet and ordered up a new Moser 12 bolt. Went with a 33 spline Truetrac and 1350 u joints, kept with a 3.55 ratio. Thought about a rear disc conversion, but that would mean I couldn't run my stock 14" wheels on occasion anymore, so the drum brakes stay. Shipping was the hard part to choke down - over $400 to get it from IN from CA. Should be here in about a week and a half.

[GOAT8U2]

I got that very same Moser twelve bolt and we started the install. They made an error, I ordered 30 spine axles and a trutrac and on accident they built it with 33 spine with trutrac so they gave me that upgrade but they screwed me for $800 on my 9" for my Grand National but that's a different story. I should've gone with Trick Chasis, not real happy so far with how they handled that.

I needed to swap to the 1350 U joint since my driveshaft wouldn't fit the 1310.

Viking rear coilovers require the smaller one inch bearing to fit the Moser shock mounts but luckily Mike at Viking offers the smaller 1" bearing for twenty five dollars.

Let's both post back and see how these turn out.

[Verdoro 68]

The cost to go from 30 spline to 33 spine was $35 so it seemed like a no brainer. I waffled over 1310 vs 1350 but figured bigger is better. I'll run a 3R/1350 conversion u-joint in the interim. At some point I'll have a driveshaft made that has 1350 on both ends.

He did mention I'll have to open up the holes on the stock drum backing plates to fit the axle bearings. Not too big of a deal. I've been researching 11" drum conversions. Might do that down the line too.

[grivera]

Goat8u2 - can you elaborate on the 800 up charge? Are you saying they off set that price to make up for the upgrades in the 12 bolt?

Ken - was the TruTrac 33 spline carrier same price as the 30 spline?

[Verdoro 68]

The 33 spine TrueTrac is $35 more than a 30 spline ($510 vs $475).

I put my order in online and a rep from Moser called me about 30 minutes later to run through the config and answer any questions. I was pleasantly surprised with their responsiveness. Really anxious to see how the Truetrac does.

[Scarebird]

I was very happy with my 8.5" tru trac.

[geeteeohguy]

Originally Posted by Verdoro 68

Just to follow up, I've been feeling some slippage with the 8.2 under power lately which accelerated my hunt for a new rear diff. I came up dry regarding reasonably priced 8.5 or 12 bolt cores locally. What I have found would need a full rebuild, new axles and a ratio change. By the time I'd be done, I'd be in the neighborhood of a Moser setup minus all the perks.

So, I bit the bullet and ordered up a new Moser 12 bolt. Went with a 33 spline Truetrac and 1350 u joints, kept with a 3.55 ratio. Thought about a rear disc conversion, but that would mean I couldn't run my stock 14" wheels on occasion anymore, so the drum brakes stay. Shipping was the hard part to choke down - over $400 to get it from IN from CA. Should be here in about a week and a half.

The front brakes do about 75-80% of the stopping power on these cars. Drum rear brakes have much better park/emergency brake action. And can be used to stop the car in an emergency. I personally would never run rear disc brakes on a street car. You'll be fine.

[GOAT8U2]

Moser screwed up my 9" order for my GN, someone at Moser called the shop my cars at, said they couldn't do the 2" chop and changed my order. I call days later to check on the pinion aspect and just inquire why I couldn't get the 2" chop done other GN guys got it. Tech says they can, low and behold they didn't know I have a frame notch, there's NO option to click this on their online form. They assumed I was factory frame without asking.

They already powdercoated it, had to chop and repowdercoat. I eat the bill because they're online form is great but not complete and while I understand the tech thought I was wrong and he didn't have all the details, I ordered it correctly. I'll pay the $800 because the chaos this creates with shops having to deal with all this sucks.

Personally,Trick Chaisis Alex wouldn't have had this issue and was $1000 cheaper, $1800 I lost on this rear end alone.

[Verdoro 68]

The 12 bolt arrived this afternoon. The FedEx guy knew exactly what it was and wanted to know what it was going in. About 10 days to my door from the day I ordered, most of that was time in transit. No issues except they charged me twice (fixed that easily with a call) and it appears they neglected to include axle seals.

This thing is beefy - especially with the cast aluminum cover! I'm sure my 8.2 will look dinky next to it. I cracked open the cover to see what the guts looked like and was disappointed to see the Truetrac had a big made in Taiwan stamp. I believe everything else is US made.

Need to figure out brake line routing and mounting as well as an axle vent. Thanks to some advice in another threat, I have Global West control arms on the way, too.

[GOAT8U2]

Reply back on how that handle the axle seals of their truly not in there.

I've heard they're getting sloppy, no SOP standards on builds and its clear they are, mine had issues too and I had to pay a lot for the product and for their issue. They're the most expensive yet their labor is lacking and you'll pay more on top of that.

[rolling money pits]

Is it an optical illusion/camera angle thing, or is the DS upper bushing pressed in cockeyed?

[Verdoro 68]

Originally Posted by rolling money pits

Is it an optical illusion/camera angle thing, or is the DS upper bushing pressed in cockeyed?

It is. I looked at some old threads in other forums and apparently this is by design. Apparently they use the same housing for G bodies which uses a different angle and they just bore the angle for the application. Looks funky though.