differential question

[PONCHO130]

in what vehicle can i find a posi trac rear differential for my 81 chevy?

[ont_guy_38]

10 bolt 8.5?

[LONGHAIR]

Unless you luck into something with an aftermarket unit......there is nothing out there worth having.
The factory part (Gov-lock) is just plain worthless. It is either "barely there" or "exploding".
Despite it's name, it is not a locking differential, it's a clutch type posi that is "regulated" by a centrifugal mechanism. It functions as an ordinary open differential most of the time and only "kicks in" as needed. It will not take much more than stock as far as horsepower.

You would be much better off with an aftermarket true clutch type posi traction. Plus it would be new, not of an unknown condition.

[wraprail]

Originally Posted by PONCHO130

in what vehicle can i find a posi trac rear differential for my 81 chevy?

Last one I saw at pic-a-part was in an 87 10 2wd suburban 3.73 posi. Just check the option tag inside the glove box. They are out there you just gota look.

Good luck!
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[LONGHAIR]

Originally Posted by wraprail

Last one I saw at pic-a-part was in an 87 10 2wd suburban 3.73 posi. Just check the option tag inside the glove box. They are out there you just gota look.

Good luck!
Posted via Mobile Device

That's a "Gov-lock" which is not the same thing. Chevy has not used a true Positraction unit since the early 70s.

[b454rat]

If you take the shafts out of 89-91 burban or blaze, you can use the 10 bolt 8.5 posi that came in mid 90 Caprices....

[PONCHO130]

Originally Posted by b454rat

If you take the shafts out of 89-91 burban or blaze, you can use the 10 bolt 8.5 posi that came in mid 90 Caprices....

would that be the same thing and would i have to look for a certain code?

[b454rat]

Codes are the same between cars and trucks. So look for mid 90s with the 8.5, will have to check cause some got the 7.6 or something, then look in the trucklid for the RPO codes, G80 is posi, locker, or whatever you want to call it...

[LONGHAIR]

G80 is the Gov-loc that I mentioned before. Don't waste your time or money on it. They suck.

[b454rat]

For a truck yes, they are junk, BUT I'm talking about a true posi unit out of I think a B-body car, Caprice, Impala and the like. Even tho it's a posi, it's still a G80, which is what they call a locking diff....

[PONCHO130]

Can they be identifyed off the vehicle?

[b454rat]

Truck govlocks have all these weird levers and crap, while the posi has springs. Do a search for govlock pics, bunch out there..

[ont_guy_38]

Any Eaton 8.5 clutch type posi will work. Camaro, firebird, nova. 8.5 started around 71 and went till atleast 81 in the Camaros, longer in some models. That is what I have in my truck and I am very happy with it. Like mentioned above, do not waste time and money on a gov lock.

[PONCHO130]

i would still have to modify it to fit my 81 c-10?

[ont_guy_38]

No, a 8.5 10 bolt is the same whether it is a car or truck rear end...just make sure it comes out of an 8.5 as the earlier car 10 bolts are 8.2.

[PONCHO130]

Originally Posted by ont_guy_38

No, a 8.5 10 bolt is the same whether it is a car or truck rear end...just make sure it comes out of an 8.5 as the earlier car 10 bolts are 8.2.

this might sound like a stupid question, but what is the difference between 8.2 and 8.5?

[ont_guy_38]

Nothing is stupid... usually the rear pot has a couple of square pegs under the rear cover...see picture. If you want to be absolute sure, just take the number off the carrier and search it, that will soon tell you.

[PONCHO130]

Are all 8.5 posi's?

[PONCHO130]

i have an 1989 suburban 1/2 ton rear end will need to check to see if its a 8.5. i was told suburbans came with the 3.73 gears. unknown if its true or not and weather its a posi or not

[ont_guy_38]

not all are posi no...is the burb 2wd or 4wd? When you get that new I think they have 30 spline axles.

[PONCHO130]

2wd

[Rich84]

89 is 30 spline.

[ont_guy_38]

Check to see if it's a posi, if it is check the width of the complete rear end and mounting perches. I think they might be the same width as your 81. Switch the whole rear end and your all set.

[i heart square bodys]

did the 12 bolts fall into the gov-lock thing ? or just the 10's? ive found a 12 bolt with 5x5 lug axles that a buddy has but im not paying for it if its a waste in the long run.

[b454rat]

Depends on the year. Early will have the Eaton style, late 70s will have the grenade lock...