Rear Upper control arm differences

FoR Years anyone who wanted to add a rear swaybar to their car always went looking for a boxed set of lowers and never paid attention to the uppers. They are different however as I found out to my dismay. I have an almost pristine set of rerar uppers but they are from a Skylark. I have always heard the difference is in the bushing. This is true. The GS used a rubber bushing with higher durometer rating. You can feel the difference with your fingernail. This was not an issue to me as I was changing the bushings anyway. The real difference is in the flange lip on the sides. Look at the picture below and you can see the thinner flange on the cleaned skylark arm and the thicker lip on my old crusty GS originals. I cannot beleive I have to try and blast those now. Alos if you can see the side of an arm a GS has a PX stamped in the side and a standard had NK stamped in it. Any GS or even a Skylark with sport suspension had the heavier arms. All Skylark/sport wagons had them as well. Anyone want to by the nice skylark arms I will list them in parts for sale. I am also looking for nice PX set.

 

This would be good info for george's website!

 

Grrrrrreat info...now that i just threw some away,2sets with that code.That hurts.my turnou:

 

Interesting. Thanks for posting.

However, I'd want to see several more sets exhibiting the same lip differences before stating this as definitive. These control arms are stamped (deep drawn?) out of a blank of steel, and the strengthening lip is conveniently formed by the excess steel which doesn't get pushed down into the die. That excess is not tightly controlled and will vary. I can imagine that the next step was for each arm to be inspected to make sure that it had neither too much lip (might interfere with other chassis components) nor too little lip (won't give enough strength). Too little got rejected. Too much could be salvaged by grinding -- or perhaps another die cut off the excess.

I'm not saying that the PX arms didn't intentionally have more lip than the NK arms; that might have been part of the inspection/sorting process. But I'd want to see more examples (and find no contrary examples) before writing it in stone.

 

I tend to agree with Brian. I've seen so many of these through the years off of Buicks, Chevelles, and GTOs and they vary so much in appearance that I always attributed it to quality control. I never knew that the factory would have put different bushings in the GS cars but anymore when you order new ones you'll simply get A-body bushings. I've never come across a situation where the bushings were different from a GS/Skylark, GTO or Lemans/Tempest, Chevelle/Malibu.

 

Just to be clear, I'm not doubting the use of two different part numbers for GS vs. Skylark, just that the difference was anything more than the bushing pressed in.

As for the application code being stamped in the arm, there are other ways for them to be identified. On my Olds 442, the upper arms have the code stamped into the steel (NJ), while the lowers have it stamped in red ink (NZ). But I have also seen NOS arms where the code is on a paper label.

 

Maybe the metal is a different thickness on PX stamped arms???

I have some and will try to get to them on Wed.

 

George hit the nail on the head. I held them together today and they are different wieghts as well The PX's are heavier...As far as ID the code was acceptable 3 ways in the assembly manual. Stamped in metal, Painted on or paper tag so it may not always be there....As far as the bushings they are different as well. The 71 Buick assembly has a chart that shows part numbers. The bushing in the regular and heavy duty uppers cary different part numbers. The bushings in the lower boxed and regs show different part numbers. On top of that none of them are the same. When you buy new bushings you can only get all the same. There is no listing for the bushing in the rear en housing......As far as the Olds goes funny you should mention it Brian. I am currently helping a friend restore a 72 Hurst Olds. It has the Olds heavy duty version which is NJ. It also has the wider lip. We measured it. The base olds unit is the same as the Buick which is NK. I guess the difference must be the Bushing between the Olds and Buick as the steel appears the same. The olds assembly does not list the bushing part#s like the Buick....As far as the bushings they were all really different. They had slightly different durometer ratings. The base units had softer rubber. I could get my fingernail much further into the softer rubber. The heavy duty arms had harder rubber. The Moog Replacements have softer ruber like the base units. The Raybestos Prof. grade appear to have harder rubber.

 

Jason, yours do have a stamp. Check the first picture in the top middle of the arm. It might be a backwards PX. Check it out.

 

Dave,

I have a set of px's. They are kind of pitted. Let me know if you are interested - $40 + shipping for the pair.

 

I wonder what year they made the change to two different arms? My 68/69 parts list only list one. They do however list two different bushing sets

I have the old ones off the GS and a lark set, I'll have to go out and see if there are any differences on the 69's?

 

Where are you finding the raybestos prof. grade stuff around here?

i don't know if this helps with the debate but here is a set of uppers i am putting in my car from a chevelle ss with the re-enforced drivers side

 

Chris there was a reinforcement used on Buicks with Automatic level control option but never saw one like your before.

 

Chris, Rock Auto sells the Raybestos Prof. Grade stuff. Thats where I got them.....................................................................................................Anyone ever seen or used the reproduction rear uppers?

 

Reinforced section is there because they came from a 12-Bolt rear car, and a 10-Bolt car uses a different upper arm on the driver's side. The 10-Bolt upper arm on the driver's side rubs on the center-section of a 12-Bolt housing! Ask me how I know . . .

 

Just pulled the two arms. GS400 the crusty one and a skylark. The bushings are different, the arms are exactly the same. Unable to find any stampings. Both cars are Flint cars, 1 month apart (June, July)

Maybe the change was made 70 on up?o No:

 

Bingo!

Check this site: http://www.leverfamilysite.com/Rear_Upper_10_12_bolt_Differences.htm

 

It's been in my browser bookmarks for about a year already :TU: