1965cutlassragtop

so i currently have a 8.2" 10 bolt with factory POSI. it is really the only component in the drivetrain i havn't paid any attention too. it seems solid as of right now, it will burn straight POSI no problem. but i have a feeling because i have a freshly rebuilt TH350 shifting hard, and some mild performance mods done to my engine which is running very strong, that the rear end may be blown soon. the car will chirp second no problem, sometimes when i'm not expecting it too so i am thinking it's only a matter of time before this rear end says UNCLE!!! from what i have read on other threads here, it seems my best option would be to grab a 8.5" 10 bolt and rebuild it. i am leaning towards a PowerTrax setup. i noticed on their website they actually have a system for the 8.2" & 8.5". so i am wondering, would i be okay throwing one of those in my current 8.2" carrier? the reason i am confused is because it says the powertrax is for "open" carriers....is my current carrier considered open?? not sure what exactly that means...because my rear end has factory posi, would that complicate the install?? and can you put any gear ratio in the powertrax or do they come pre loaded with gears? just trying to figure out what my best option would be and what it would cost. thanks guys!!

1965cutlassragtop

i was also considering the Auburn LSD Pro Series....

gearheads78

I wouldn't worry much about it unless you are doing drag race launches on sticky tires.

Oldsmaniac

X2...tires spin all is fine, big tires bite, things break!

1965cutlassragtop

i see your point. but aside from that, can anyone clarify the "open carrier" situation, whether mine is or isn't?? and let's pretend i started this thread with...."i blew my rear end, what are my options?" only because i know this will be my next area of concern, whether i just pull it out to sandblast it and repaint it, or replace the carrier bearings, or go to a bit lower gear, say 3.23. i figure while it's out, let's get her back to 100%. not worried about money, i try to do things once. so if i end up pulling that rear end, it's gonna be rebuilt, so i know that things are operating correctly. if i can upgrade it during the process, i would like to. i would really like to keep the factory rear end since it is original and just beef up the interior components. i really like that Auburn switchable differential. from limited slip to locked with a push of a button. not sure if i could use that in an 8.2 10 bolt though??

Oldsmaniac

An open carrier where I come from means a non posi or non limited slip rear.

GAOldsman

This should help identify which one you have.

http://wildaboutcarsonline.com/cgi-b...=9990382924295

and this

http://wildaboutcarsonline.com/membe...2011-04-07.pdf


Scot

gearheads78

If you are set on going through yours I would order a 8.5 from Brian Trick and don't look back.

1965cutlassragtop

That second link really will help, I'll get under the car and check the codes on the rear end. But I take it I do not have an open carrier, although I should already have the whole POSI assembly already there. Guess I better look around the area and try to find a shop who rebuilds these things. Sounds like I could just rebuild my current setup with new parts and swap out the gears for 3.23, and get a little more pep around town. I Don't usually take this car on highways too often....I try to stick to the back roads:-)

1965cutlassragtop

after speaking to a distant friend of mine who builds race cars, i've desided to stick with what i have, but freshen it up. i will be changing the fluid, installing a rebuild kit w/ bearings, swapping my 3.08 to 3.23, and i'll probably clean up the housing, repaint it, and add a new differential cover for looks:-)

monzaz

If you are street bound the 10 bolt 8.2 will do the job. Just pay attention to the specs and you will be good. New bearings and seals and she'll run like new again. Jim

jag1886

You should try one of those preload differential covers they make now, years ago they used to built a preload main cap strap, I broke a bunch of rear ends in an old Chevelle I had until I built a rear end and used those and it never happened again. Preloading the main caps helps on 10 bolts for medium HP cars.

Mark71

Does that apply to a mostly-stock 455 build? I don't have a reason to worry now, but I've been considering the upgrade someday...

I've always heard I need a 12 bolt and TH 400 with a 455, that's why I ask.

507OLDS

Mark,
If you have a 71-72,it should have the 8.5" 10-bolt.If that is what you have,that rear is a great piece.

J-(Chicago)

In my opinion A mostly stock 455 in 1971 couldn't really hurt anything, unless you're really trying hard.
Maybe it could break a worn out 7.5 rear, but 71-up 455 motors were dogs.
I've been beating the snot out of a Th350 behind my 455 at the strip for a few years already.

Mark71

Wow... Ok, I am really glad to hear this. I currently have a 350 and want to (someday, once I've convinced the wife) to move in the direction of a 455. There's two problems with that plan, though: 1) I don't have the cash to do the entire drivetrain, etc. at once and 2) finding a decent 455 core is a lot harder than I thought.

@Brian- I've got the 10 bolt, 8.5 inch rear which is from 71 (according to the previous owner - gotta check it). It is an open rear, though, not posi. Is that the one you are talking about?

I only ask because people around my area seem to think 12 bolt or Ford 9" are the only way to go...

-Mark

507OLDS

It doesn't matter if your rear is an open or posi.You can install anything you want into it.yes,some people still believe that you need a 12-bolt Chevy or a Ford 9",but that is not so.

JamesPDX

I replaced my GM 7.5" 2.93:1 differential with an open GM 10 bolt, 8.5" 3.08:1 unit that I picked up for a song and dance. The purpose was to get the 8.5” box. Other than reworking my propeller shaft (drive shaft) that was out of balance at 50-60 MPH, and making it 1.25” shorter (the balance work was included), one axle had a slight wobble when rolled on the floor (it was bent), and needed to be replaced. All other internals were in good order or were replaced.

When it was completed, the first thing that I noticed was that everything ran smoother (no more vibration), but there was an increase of 50 RPM at 60 MPH, and very little noticeable startup from the lower gears. The same would be true when changing from 3.23:1 to 3.42:1. As soon as I can swing for it, I'd like to replace the 3.08:1 gears with 3.42:1 (an increase of 450 RPM at 60 MPH) and maybe an Eaton positraction. The OD should help with the hi-way speeds, and the gears would keep the engine in its power range allowing for better hill climbs in OD.

I read about several types of traction devises and asked several people for their thoughts on them. There is a real mix of opinion out there. I think it really comes down to what the purpose of the vehicle is. I want less work and lower temperature for my 200-r4, and better economy and startup traction in city driving. The overdrive will take care of freeway driving. I do not need more than a 1200-1500 RPM stall converter. I read and heard comments about positraction devices not being good in rain and ice. I’m concerned about this. There does not seem to be enough evidence to backup the claims. There needs to be more specifics about this problem, and under shat conditions.

I’m currently looking at various aluminum covers for the unit to lower the box temperature. Mag-Hytec manufactures some great units, although they are being advertised for trucks with GM 8.5” boxes. Are these interchangeable with car boxes?

507OLDS

If someone is claiming that a posi unit is not good in rain,or on ice,then they should not be driving.That was one of the reasons they invented a posi unit. My previous plow truck was an 85 GMC.They call those a 4x4,but technically they are not.With open differentials in the front and back,your right rear & left front are the wheels under power,when moving forward,and the left rear & right front are the wheels under load when in reverse.We get some serious winters here,and that was one of the first things I did to that truck.I installed a posi in the back and in the front.After I did that,it was a true 4x4,or the modern term AWD.I had locking hubs,so simply unlocking them made it fine for regular driving.I couldn't get that truck stuck if I tried.
Yes,a rear wheel drive car with posi,will pull the rear of the car to the right,if trying to acclelerate on ice,whereas a non-posi car will pretty much stay straight,but if you're stuck,you're stuck.

JamesPDX

Those were very near to my thoughts. Now that you mentioned it, I recall hot rods in the '60s pulling to the side (forgot which) with peddle to the metal, but otherwise they worked quite well and had no more slipping on wet cross walks or RR tracks with the posi. This is why I want to install the posi.

I forget that opinions out there are not always so great.

Thanks Brian,

nonhog

71-72 8.5 is a little wider than a 65 correct?
Are they hard to narrow? Then add Ford ends?
Just wondering?

Project Grandpa

If it doesn't leak and makes no noise I would reccomend leaving it be. You are in the cool spot. 8.2s hate torque. So do 330s. A 330 is a horsepower engine. Great midrange. That 8.2 should live a long life as long as you drive it and it holds fluid well.

507OLDS

The 64-65 rears are 5/8" narrower on each side,compared to the 66-72 rears,that came under the Cutlass/442's. The different in width is on the very end of the axle tube,from the shock mount perch,to the end.There is not a lot of room to work with,to narrower the wider ones.When I do this,I slice the shock mount up the middle & remove it,to give me more room to work.I cut the ends off & install the Moser #7900 ends.These ends allow you to run the big Ford bearing,or the Timken SET-20,AND they have the same GM bolt pattern on teh flange,so you can reuse your existing backing plates & brakes.No need to use Ford brake parts.Once the work is done,I weld the shock mount back on.Done.