O.K. after some exhaustive footwork. I have come to a conclusion on the stock OEM rear upper control arms 1968-1972. Seems the 12 bolt arms have about a 1/8" ground off the bottom of the flange, and a 1 1/2 x 1 1/2 thin steel plate welded to it. Seems the 10 bolt style arm (which is exactly the same, sans the plate and stock removal)will not accommodate a full motion on a 12 bolt rearend due to the larger ears on the punk-house. Has anyone seen this? I just spoke with a fella that refurbishes these arms and has instructed me as such. Can anyone out there look at their uppers by the housing w/ 12 bolt style and confirm this? Better yet does anyone have these 12 bolt style uppers for sale?

I am installing the old stock 10-bolt arms on my new 12-bolt this summer and am eager to here the input from everyone on this... It's the first I've heard about it, but it sounds like a very simple modification. Thanks for posting it

Texas, I sent ya a photo. Would'a put it up here, but don't know how.

Steve

Here it is... Thanks Steve
http://www.austinmarshall.com/chev_pics/rear_uppers.bmp

Yep, the one on yhe left is 10 bolt, the one on yhe right is 12 bolt.

That is strange i changed from a 10bolt rear to a 12 bolt rear and did not change my control arms.

I believe the small plate welded on the side is for stength also.

are these on both sides?
I looked under mine and only found one (which someone may have changed at some point)

Ya, both sides, but only on one side of each arm, right?

so which way are they supposed to be installed
with the welded plate to the outside or the middle of the car?

I am further investigating this now. I have a few fella that have reported that the arm we speak of is only on one side. I'll report my findings on this Mon-Tues. Maybe some here in the group could crawl under thier cars and report their findings.

So far I have 2 reports of cars with one of these re-enforced 12 bolt arms being on the right side. I cannot confirm if these autos are original, and am still awaiting a reliable source to crawl under and look on an original known car. I am however now leaning toward this setup possibly being F41 specific? Anyone that can confirm this on their car would be helpful...any takers?

I have only one on mine and it too is on the passenger side

I also have a four speed car

will never know if the car had an f-41 suspension

no build sheet and this car has been through the ringer

I never noticed the difference. I have one "reinforced" control arm but it was located on the driver's side. Attached are photos from the dismantling of the rear suspension and the arm after powdercoating. Neither show the plate clearly, but it can be seen. I have owned the car since 1987 so any modifications would have been made before then. Though I do not have the build sheet, there is no indication that this car had the F41 suspension.

http://www.chevelles.com/forums/attachment.php?attachmentid=34

http://www.chevelles.com/forums/attachment.php?attachmentid=33

OK, I'm to stupid to get the pictures to post here, so click the links!

Tom, is the plate on the right or left on your car? So far I have actually have spoken with 2 other persons that verify that the reinforced arm is on the drivers-side with the plate in-board toward the driveshaft.

it is all in pieces since I took it apart

but I reassembled the arms to the stiffeners that link the two together
and did not take notice properly
I will go out and make sure

duh

i'm a moron
I must have looked at it wrong
it did come off the drivers side
I'm glad someone caught that
so after they are blasted and the bushings are changed
I can reassemble it correctly
thanks guys

Thats 4 confirmed cases of driver side w/ the plate in-board toward drive shaft....can anyone else confirm this??

Neuman, I think if you decode your cowl tag, it will specify F41. Also your links to the photos are invalid according to the site. I am leaning on the fact that only one of these arms should be present on the divers side. Although the jury is still out.

steve

For those of you interested, I'll try to re-post the pic of my rear control arm before removal.

<sigh> here's a link to my web page showing the arm

http://www.old-capitol-club.com/chevelle_005.htm

OK Fellas, I found this web page. This should now confirm that only one goes on the drivers side, and that there is in-deed a difference between 10 bolt & 12 bolt arms.......steve

http://www.grimers.com/vehicles/olds/12bolt/

pulled out 3 12 bolt rears from original EL cam cars, none had these arms.

Tom, is the plate on the right or left on your car? So far I have actually have spoken with 2 other persons that verify that the reinforced arm is on the drivers-side with the plate in-board toward the driveshaft.
yes mine also is inboard toward the driveshaft

I did not bother taking a picture and posting it because it is to hard to see

but on 4-14 of the chassis manual you can see this arm in figure 34 & 35 and it is used with the "heavy duty carrier"

Guess this solves it. Thanks for all the input here guy's

steve

oh yeah I forgot to mension it is shown on the drivers side with the plate facing in towards the drive shaft

Neuman, I think if you decode your cowl tag, it will specify F41. Also your links to the photos are invalid according to the site. I am leaning on the fact that only one of these arms should be present on the divers side. Although the jury is still out.

Does the cowl tag show the F41 option? I thought that info would only be available on the build sheet.

I thought it was on the cowl tag info. If I remember right it popped up on my tag info. Its been awhile though. Still wouldn't hurt to decode it.

I don't know if you still want the upper control arms but I have a set that I sandblasted, have poly bushings, and are painted chassis black if somebody wants a set. I haven't used them since I fixed them up.

All the '70 SS cars came with F41 and the reinforced arm. In '69 F41 was an option. Our cars have the standard and F40 with the open arms and the reinforcement. I have another 12 bolt rearend from a '69 350 Chevelle with the standard suspension and it has the reinforcement as well. I think you will find that this reinforcement came with all 12 bolt rear ends. The 10 bolt arms seem to interchange ok as we have swapped 12 bolts into 10 bolt cars. There is always the chance that the operator could have picked up a 10 bolt arm by mistake when asembling the suspension, which could account for some different setups.

Here is a picture of mine before disassembly - 70 SS 4spd.
http://www.chevelles.com/showroom/70Z15/Feb22n30.JPG

Great, a picture is worth a thousand words. I now have confirmed all. That this is indeed a one arm deal. I have discussed this not only here, but with about 7 other Chevelle guy's in my area. Thanks for putting the final nail in the coffin on this one Tom......Steve