10 bolt vs 12 bolt??

[chicane67]

Ya know... now that you mention it... I do remember someone posting as Chicayne in years past.

[SicMonte]

id hate to say this...but my factory stock 7 5/8" 10 bolt...has never been replaced...and is supporting a 410hp motor and is abused all the time. I have changed the fluid twice. Now..I am waiting for the big blow up...but it is fine for now...and it is the "weak" one. I have had the car for over 5 years now...and the rear is still doing posi burnouts and all. Factory G80 code....3.73 gears..posi rear end...7 5/8 10 bolt.

[Tiger]

hey sic,

I'd start preparing the new axle, you know, just in case

[SicMonte]

yeah i know...its bound to happen....

[Bandit]

Another little tidbit...in case you are looking for a 10-bolt...you should know that the number of bolts holding the cover on will not tell you which ring gear is inside.
Basically you want to get one of the 10-bolts from a '70-81 (2nd gen) camaro/firebird, that's the 8.5" version. (Of course they put them in other vehicles too but there are plenty of junk 2nd gens around to pull from) The first gens have the sucky 8.2's and the 3rd gens have the sucky 7.5's, stay away from both. An 8.5 10" will doubtless handle whatever you're doing with it.
Or, you can get a 12-bolt, but keep in mind that not all 12-bolts are strong, like someone mentioned earlier.
Or Ford 9"/Dana 60 if money is not an object...

Here's an outstanding tech article that helped me immensely...
http://www.chevyhiperformance.com/te...ication_guide/

[Tiger]

Hey Bandito.
AFAIK all 10bolt covers have 10bolt ring gears inside and all 12bolt covers have 12bolt ring gears inside.

[Bandit]

Hey Bandito.
AFAIK all 10bolt covers have 10bolt ring gears inside and all 12bolt covers have 12bolt ring gears inside.

Huh? I'm not disputing that, all I am saying is that you can't tell the SIZE of ring gear inside from the number of bolts on the housing cover. You have to open it up to be sure. Thought that was important because it's a common myth.
Sorry if I was unclear, Tigger.

[Tiger]

I re-read your post and its my mistake.
and then I dont want to piss you off as you are too close..... :o)

ciao!

[MarkM66]

Hey Guys,
According to Richmonds site a 8,5" 10bolt has 8,5" ring gear and a 1,626" pinion shaft diameter, the 12bolt is 8,875" and 1,625"pinion diameter.

The 12bolt is a bit stronger but they are nearly as strong as each other and would both be really hard to break on a street car.
I'd stay away from the other 10 bolt axles though.

Also, I believe the 12 bolts have 30 spline axles, and the early 8.5" 10 bolts have 28 spline axles. The newer 8.5" 10 bolts that come in the later model GM trucks have 30 spline axles. But a carrier that will accept 30 spline axles will work in a early model 8.5" 10 bolt. Obviously, new axles will need to be purchase.

Given that, it looks like 8.5" 10 bolt is pretty close in stregth to a 12 bolt.

Is that correct Tom, (Chicane67)?

[Tiger]

According to my sick brain thats correct Mark.
just one addition from me, the 30spline axles from a 12bolt will fit in a 10bolt carrier and viceversa.

[chicane67]

Also, I believe the 12 bolts have 30 spline axles, and the early 8.5" 10 bolts have 28 spline axles. The newer 8.5" 10 bolts that come in the later model GM trucks have 30 spline axles. But a carrier that will accept 30 spline axles will work in a early model 8.5" 10 bolt. Obviously, new axles will need to be purchase.

Given that, it looks like 8.5" 10 bolt is pretty close in stregth to a 12 bolt.

Is that correct Tom, (Chicane67)?

You are correct sir.

[big gear head]

12 bolt axles will work in the 8.5 10 bolt IF you reduce the c clip button thickness from .312 to .250. If not then the cross shaft will not go back into the differential.

The Camaro had the 8.2 10 bolt up to '70. Starting in '71 all Camaros got the 8.5 10 bolt. In '82 they got the 7.5 10 bolt.

The Nova got the 8.5 10 bolt in '72, and they are a direct bolt in for the '67 to '69 Camaro. They have 28 spline axles, which makes them just a little better than the 8.2 10 bolt, which also has 28 spline axles. They can be upgraded to 30 spline axles with a new Eaton posi, which will bring it up close to the strength of a 12 bolt, but still not quite as strong. The size of the pinion shaft is not the thing that determines the strength of a rear end. It has more to do with the diameter of the ring gear, and the 8.5 falls short of the 12 bolt by 3/8 inch. That might not seem like much, but when talking about rear end strength it is a lot. GM thought it was improtant enouogh that they increased the ring gear diameter of the 7.5 and 8.5 by 1/8 inch to make them stronger, but they increased the axle size in both of them first.

[chicane67]

Holy sh*t... its Freddy.

Glad to see you in the ranks old man !! It'll be nice to have another old school diff cat around.

[Project69]

In actuallity a Built 10-bolt 8.5'' can with stand some punishment, ive seen some take a car in the 10's with slicks on many times and nothing go's wrong, with those the only weak point are the axle shafts, and since there c-clips when those brake, say good bye to whatever wheel is attached to it cause they will roll out of the axle housing end, (pretty neat to watch though) haha. But I have a 10 bolt in mine and it works fine, Id recommend a 12 bolt if your running a trans brake with a not to wild stahl and slicks cause that initial snap of torque will cause strain on that pinion and teeth.

[big gear head]

I was wondering if that was you. Haven't seen you on the Camaro board lately and I wondered what happened to you. It's Jim isn't it?

[chicane67]

PM sent.

[big gear head]

Sorry Tom, I'm bad with names. I knew it was 3 letters.

[chicane67]

3 letters.... yeah, I was thinging more along the lines of 'ass' or something colorful like that myself.