[b-man]

Originally Posted by kyle_blake

What is a TA cover?

https://www.taperformance.com/products.asp?cat=48

I have a TA cover that I need to install on the 8.5 in my Tempest. I chose the 8.5 for a little less unsprung weight than a 12-bolt and a little less internal friction, my car is built for cornering rather than straight line performance. Still rivals the strength of a 12-bolt just in a little lighter package.

[JLBIII]

I currently have the original 8.2 housing with 3.36 Yukon gears, Eaton posi and B&M cover behind a 461 stroker in my 68 FB. Original plan was to build it for cruising and get a couple time slips. Wound up pulling the numbers matching engine and TH400, storing them under my bench and having a completely new engine and trans built. Had a lot of fun at the track last year. I plan to hit the track more often this year so I recently ordered a new Moser 12 bolt with 3.91 gears, 33 spline axles and Trutrack carrier. Car already has a Stage II TH2004R from Extreme Automatics. Wanted to keep the car GM appearing plus I had bad experiences with Ford rears almost 50 years ago. Granted they weren't 9" but the stigma is still there.

[Jay S]

The TA cover girdle or other comparable 10 bolt girdle covers for an 8.2 is the same as a 8.5. You can get it and run it on an 8.2 10 bolt and move it over to a 8.5. Some knock offs are only about $150 new. It both keeps the case from flexing for better teeth contact under a load, and reinforces the carrier caps. With a valuable N case and more than 400 HP in front of it I would want to run one. I like the deeper cover versions that add extra strength and also add an extra quart of oil.

The cheapest upgrade for an 8.2 in an A body is by far the 71 and 72 Olds and Buick 8.5s. The 8.5 have bigger U joints and bolt in axles that do not taper down like a 12 bolt or a 8.2. The driveshaft usually has to be shortened some, same as running a 12 bolt. The stock axles are 28 spline but they do not taper down like a 8.2 or a 12 bolt, the stock the 71 and 72 bolt in axles are strong enough to get a street car deep into the 11s. For drag racing you do not need the c clip eliminators either. The 8.5s weak spot is the stock carrier, but can also be upgraded to a 28 or 30 spline axles and better carrier, or even 35 spline and spool for drag racing. You can also upgrade the 8.5 to newer style 8.6” ring gears. From what I understand the 8.5 carrier’s are Nodular (not completely sure on that though), but I know all the OEM A body 12 bolts are grey iron. The two have the same pinion dimensions, so the nodular 8.5 has more pinion support than a 12 bolt. Find someone that is parting out a 72 Buick or Cutlass and you will find a cheap 8.5. The Cutlass does not have the typical 8.5 markings, and get passed off as Chevy 8.2s. Easiest to find and usually price the same as an 8.2 cause they don’t know what it is.

[locomotivebreath]

I run the TA cover on a 3.90 N unit . I’m not a drag racer and have a more modest 420hp 406 . I also bought thicker axle
retaining plates from Jim at http://www.jdrace.com/ in Ohio . They are supposed to provide more support for the sealed axle bearings . You can’t find a 8.5 unit anywhere around my neck of the woods . I’m really considering a moser instead of a rebuild of my 8.2 when the time comes .

[Skip Fix]

FWIW my 78 TA stock 8.5 axles have a lot of low 11 high 10 runs on them. just recently upgraded to 30 splines in it. Many of the bearings in an 8.5 are identical to 12 bolts.

[Jay S]

If you plan to hire someone to rebuild and set up a 8.5 or 12 bolt, cost wise it becomes close enough you are likely ahead getting the complete aftermarket 12 bolt that drops in.

[i82much]

i went strange S60 years ago. pretty sure i did that because they didnt have a 35 spline truetrac for the 9 inch, only dana 60 at the time. my car is only 550 hp or so and is a street car so probably way overkill. but honestly i never thought once about how it would look under the car, just that it was the strongest diff available and they were all about the same price from what i remember.

i definitely get that the 12 bolt will be plenty for your intended use and look "right" under your car ... but what if you decide to do a procharger or turbo one day? these cars are never finished .... like guns and roses said, "i used to do a little but a little wasnt doin' so a little got more and more ..."

[Jay S]

Originally Posted by i82much

i went strange S60 years ago. pretty sure i did that because they didnt have a 35 spline truetrac for the 9 inch, only dana 60 at the time. my car is only 550 hp or so and is a street car so probably way overkill. but honestly i never thought once about how it would look under the car, just that it was the strongest diff available and they were all about the same price from what i remember.

i definitely get that the 12 bolt will be plenty for your intended use and look "right" under your car ... but what if you decide to do a procharger or turbo one day? these cars are never finished .... like guns and roses said, "i used to do a little but a little wasnt doin' so a little got more and more ..."

That is some good overkill..aftermarket block and a 35 spline S60 for 550 HP. That’s awesome. Did your grandparent’s build brick outhouse’s for a living. Lol

[i82much]

Originally Posted by Jay S

That is some good overkill..aftermarket block and a 35 spline S60 for 550 HP. That’s awesome. Did your grandparent’s build brick outhouse’s for a living. Lol

i broke a couple 8.2's and a muncie years ago ... i was a little gun-shy when i put the car together.

[Verdoro 68]

Maybe I'll add a T/A cover as cheap(er) insurance while I gather funds for a 12 bolt. Not sure I trust it enough to save the rear on a 1/4 mile run, but it's not going to hurt anything.

Speaking of JD Race, he's got a few 8.5s on his eBay store for under $2k. Seems like an economical path from a trusted source.

[Skip Fix]

So for you 12 bolt 33 spline guys does the bigger axle and spiders make the case thinner and break there?

[b-man]

Originally Posted by Verdoro 68

Maybe I'll add a T/A cover as cheap(er) insurance while I gather funds for a 12 bolt. Not sure I trust it enough to save the rear on a 1/4 mile run, but it's not going to hurt anything.

Speaking of JD Race, he's got a few 8.5s on his eBay store for under $2k. Seems like an economical path from a trusted source.

That’s where I had mine built. Kinda hard to go wrong, just be sure to upgrade to an Eaton posi with 30-spline Moser axles if you do decide to do the 8.5. Also make sure it’s the ‘71-‘72 Buick/Olds version with the bolt-in axles and tapered roller axle bearings.

Also you’ll be able to reuse the TA cover since the same one fits 8.2 and 8.5 BOP rear ends.

Back in my racing days I remember seeing an 8.5 under Jim Wanger’s red 1974 T/A running nitrous that was driven by ‘Dirty Ed’ Dufrene. The T/A was a stealthy street race car with no really visible traction aids (pinion snubber and probably clamped leaf springs) and it was running in the 9.40s at over 140 mph at LACR’s 2700 ft altitude.

[Verdoro 68]

Originally Posted by b-man

That’s where I had mine built. Kinda hard to go wrong, just be sure to upgrade to an Eaton posi with 30-spline Moser axles if you do decide to do the 8.5. Also make sure it’s the ‘71-‘72 Buick/Olds version with the bolt-in axles and tapered roller axle bearings.

Also you’ll be able to reuse the TA cover since the same one fits 8.2 and 8.5 BOP rear ends.

Jim's got a '71 Cutlass 8.5 with a 3.42 Eaton setup ready to go that looks like a pretty good option. I wanted to keep with 3.55s, but I don't think stepping down to 3.42s would upset my combo.

[b-man]

Mine has 3.42 gears as well, that’s a decent gear for street and not too bad on the highway with a tallish tire. You really won’t notice the difference, 464 cubes doesn’t really need any gear steeper than 3.42 on the street and in fact 3.08 would be plenty.

I’m running mine behind an overdrive auto trans so the highway RPMs will be pretty low.

A 12-bolt would be nice but if you’re trying to keep within a budget the 8.5 is not only priced right it’s also plenty strong for your needs.

Not everyone is planning on building a 6 or 700 horsepower beast in the future. If you ever did well then changing the rear end out to something stronger wouldn’t be a big deal.

[Greg Reid]

What kind of HP/torque are we looking at before it's time to worry about breaking a stock, nodular Pontiac LS rear? 3.55 for instance.

[b-man]

Once you start using sticky tires is usually when you start spitting out the stock limited slip 8.5 diffs, I’m sure they will handle 400 horsepower no problem if the tires can spin.

Your guess is as good as mine when you’re talking about 8.2 cone-type posi units. I had a decent 3.36 posi 8.2 and I sold it so the next guy could deal with whatever might happen to it in future. The later clutch-type posi units are much better.

I plan on upgrading my Le Mans convertible with a Buick/Olds 8.5 factory limited slip and 2.73 gears to replace the one-legger 2.56 8.2 rear. My 421 HO is a mild build making maybe 350 horsepower.

[Gach]

I know its not cheap but definitely going with 12 bolt and the TA is cheap insurance especially if you want to play once in a while. In the end we all want to add more power, specially if down the road you want to Boost that baby up to 500 hp, and put some stickies on that baby. Coming up through ranks of muscle car error, and seeing 10 bolts weather the 8.2 or the 8.5 grenade when you least expect it. Everyone hunting for 12 bolts to replace them.

[GOAT8U2]

Not trying to thread jack but I'm in the same position as the OP, rear end options.

606tq/569hp 462ci on 295/55/50 possible 295/65/15
I've got the 69 XH nodular rear with 3.55, part of me wants to upgrade this since..
I've got rear disk brakes on it already.
This rear end is factory and nice, I'm not dragging the car but at 4000lbs and possible 30" Street R tire to hook, it'll get some abuse.

What if me and the OP wanna keep the 8.2...
Moser 31 spline and what new gears etc, can the 8.2 handle the torque and occasional street launch for us???

I'm thinking it can and if we update the parts with only the level of hooking the tq comes into the equation. Street tires add no real load on the rear end but dead hooking is now a big change, 30" x 12" Street R tire.

Thanks and sorry OP if this Jack's your posts.

[b-man]

Don’t keep the 8.2 rear.

Upgrade to something better rather than waste money hoping the 8.2 will withstand 570 horsepower’s worth of abuse for any reasonable amount of time.

Hooking up will break the 8.2 so sell it before you make that mistake and just move on to something better, you’ll be money ahead in the long run.

[Stan Weiss]

Originally Posted by Greg Reid

What kind of HP/torque are we looking at before it's time to worry about breaking a stock, nodular Pontiac LS rear? 3.55 for instance.

While I don't have an answer for you. I would have to guess that rear ends like transmission (both manual and automatics) would be rated in torque capacity.

Stan