442_Mustang

A buddy of mine who sets up rear differentials for a living was telling me that the axles in the Type O 8.5 in my 72 Cutlass has smaller weaker axles than the old "C" clip rear ends. Any truth to this? I think what he wants to do is sell me a 12 bolt from his old scab Malibu.

J-(Chicago)

Well, for starters, GM Type O and a GM 8.5 are 2 different things.

Type O has a 12 bolt cover, and a 10 bolt ring gear, and splines on a 60 degree angle. The type O axles and pinion are weaker than a regular 8.5.

The 8.5 has a 10 bolt cover and a 10 bolt ring gear.
If you have an 8.5".... Keep it. You probably have an 8.5 unless someone changed it.
I'd rather have the 8.5" than a type O or a chevy 12 bolt.

507OLDS

If your car has the original 8.5" 10-bolt(10-bolt cover/10-bolt ring gear),& your friend thinks the 12-bolt Chevy axles are stronger,then he better find another job.The 71-72 style 8.5" 10-bolt axles are nice axles,& are actually thicker than most factory 12-bolt chevy axles. Yes,the 12-bolt Chevy has 30-spline axle,compared to the 8.5" 10-bolts 28-spline,but the Chevy axles are tapered right before the spline,so that thinner area is your weakest point,& most of the time that is where those break.If you are going to add splines,you should make the rest of the axle thicker.The other plus that you have is that your 8.5" 10-bolt has bolt-in axles,no c-clips,& the axle bearings are much bigger than the Chevy axle bearings.

442_Mustang

Yes it's origional.He was telling me that those bolt in axles are weaker than the standard c clip axles. I think he was scamming me. Thanks guys.

monzaz

Well, here we are on another debate...lol

An axles strength is how well it was manufactured...period. The type of metal and mix will make all the difference.

YES usually the size will make the biggest difference...But a better mix of metal at a smaller diameter will hold just as well if not better.

I would have to say it will be a toss up on strength. Most of the 1968-1972 factory axles had the taper problem solved... The very early chevyII and chevelles were really bad offset taper and the axles did not not even have a true straight conical taper from the spline which made them the worset...lol.

It looked like a piece of GUM stuck on the end of a tapered steel punch for and axle...lol

The nice thing about the 8.2 and 8.5 71 72 is the fact that the axle was retained and bolt in. The c-clip IF you did have breakage was free to go for a walk right out of the housing.

I personally have had a 12 bolt chevy with stock GM 12 bolt axles in my car that I run with slicks and been 12.00 ...NO issues. Just remember a lot of breakage occurs for reason more than not of neglect then instead of RAW power. Most likely there was some thing already a miss and the power just pushed the axle over its point of tolerance. You will see more breakage under HOT lap conditioned when metal is malleable and then high torque loads are applied....REASON number 1001 for better ALLOY axles that stay stable under HOT conditions under load.

OR you can flip a coin....

Jim - J D Race

507OLDS

I've had plenty of 68-72 12-bolt chevys,& have one apart right now,& the shafts don't look any better than the earlier ones. Yes,we will debate this forever. Yes,there are other factors that play into this,but to say that the 12-bolt chevy rear is superior to the 71-72 8.5" 10-bolt,from the 71-72 Cutlass/442,Skylark/GS,I don't think so,but then again,I don't own a Chevelle.Those guys have a different mentality,and their car can't function without one.