GlennLever

Yes, there is a difference.

The rear upper control in the top of the picture is a stock 10 Bolt control arm. The rear upper control in the bottom of the picture is a stock 12 Bolt control arm. As you can see, the 12 Bolt arm is notched and reinforced below the bolt hole. These control arms are the same for all 1968 through 1972 GM A-Body cars



This picture shows a close-up of the 10-bolt upper arm. This arm is exactly the same as the 12-bolt arm but it was not ground down and not reinforcement plated has been added. You can modify your arms to create a 12-bolt arms and my next post will show you how to do that without buying expensive aftermarket arms.



This picture shows a close-up of the 12-bolt upper arm. This modified arm was only on the driver’s side. There were no clearance issues on the passenger side. There’s a reinforcement plate spot welded over the hole from the factory. This was done because the 12 Bolt rear end chase is larger than the 10 Bolt rear end. The arm was ground down to create clearance needed for the rear end, the plate was spot welded to the arm to restore the strength. You can do this modification.



This is a 12-bolt upper arm on a 12-bolt rear. Not shown is that the passenger arm. These (passenger) arms are the same for all rears, no clearance problems.

Sorry for the poor picture.


This is a Non-12-bolt arm on the 12-bolt rear. Note the interference with the carrier housing.

oldcutlass

Good to know, thanks for bringing this up.

joe_padavano

Thanks. I assume that when you say "12 bolt" you are referring to the Chevy 12 bolt axle. I've never seen the reinforced arms on an Olds with a Type O axle, for example.

Octania

that's what I was just thinking
I have never seen one with reinforcements, but I have not done any c type final drive cars

oldspackrat

What Joe & Chris said.

MDchanic

Wow. Why have I never heard that?

- Eric

GlennLever

This is the rear end that came out of my 1969 Cutlass and it had the control arm with the patch on it.

oldspackrat

I don't know rear ends well enough to tell from the cover which one it is but I know the Olds. rears have a threaded boss in the top of the casting where the rubber brake hose bolts into the housing. If that is not there it is not an original Olds. rear end unless it was made in Canada? I think the Canadian built cars used Chevy rear ends but not sure what years they did that.

wr1970

Hmm food for thought!! But i failed to see how that helps with load conditions on the bracket. Maybe someone can explain as it should be upward load.Those 10 bolt brackets on my rear have a washer under the nut and head that i added. Now on my chevy rear i welded the top control arms u channel with plate steel for extra strength. Never had a problem with the part as shown by these pictures.

GlennLever

The plate shown was a factory modification. Who knows, someone in the past ownership of the car put that arm in, but I believe the vehicle was all original. It certainly appeared so.


Sorry to create a controversy.

70Post

No controversy caused...most here are looking for info and this is a part/feature many have seen and wondered about. Maybe that was either a non-Olds deal or possibly something that GM incorporated as a revision or maybe even plant specific....who knows?

I've pulled A LOT of these arms from original '70 442's/W30's/Cutlass's and off my own cars....none had the reinforced arm feature. I'm not saying that it's "set in stone" but haven't seen it on any '70 Olds's and '70 or '72 Buicks that I have worked on/own.

wr1970

I don't think you started any controversy!! I will be looking at those control arms more closely from now on! Thanks for posting without your post and post like this the information of what may be out there drops to Zero! Again thank you.

tru-blue 442

I just Had to go out and peek under the 69 this morning.
Stock 3.23, no reinforcements on mine. Good thread, I am intrigued
to see if an answer comes, Canadian built FE-2 suspension package, perhaps?

GlennLever

The patch would only have been on the driver's side arm on the inboard side of that arm.

joe_padavano

Glenn's rear axle photos definitely show a Type O axle (which is NOT a "12 bolt", despite the number of bolts on the cover - there are only ten bolts holding the 8.5" ring gear to the carrier). As I've said, I've never seen that reinforcement on a Type O. I do have two untouched 69s, my 442 and my H/O. Both are Lansing cars. Unfortunately, we're getting 10" of snow right now, so I won't be looking under them anytime soon.

GlennLever

That is a good point 12 bolt does not mean 12 bolts in the cover, but 12 bolts holding the ring gear to the carrier

Octania

"Sorry to create a controversy. "
==================
yeah, don't make that mistake again because we HATE talking about minutia and details and learning about new variations of parts... j/k

Can we call it a "reinforcement" instead of a "patch" - the latter sounds like something was broken or done wrong initially.

I find it hard to believe that there would be two different upper control arms, and only the left one is reinforced. The more identical parts, the better, from a manufacturing standpoint.

The gray rear end appears to be the standard issue 1967-70 or so Type O 12-bolt, with the smooth round cover. Any chance that '69 Cutlass was Canadian built, therefore issued with the type-C 12-bolt 12-bolt, therefore the reinforced UCA per current best guess/ theory? I believe only the 68-9 Cutlasses built in Canada were made with the C type 12-bolt, the Lansing made cars came with the O type 12-bolt, even if the car had a 350 engine.

Mikes442

Parts book shows that in 1968 with the "C" rear, the Right side was the same upper control arm as the "O" rear and the Left side had a different number, one for the F-85 exc. 442 and another number for the 442.


The differences are the bushings(softer/harder). So it looks like it was for the Canadian built cars with the "C" rears.


There are two different upper control arm assemblies, arm is the same, just in the bushings only.