I noticed in my 72 Assembly manual, that the BB cars have a different part number for the front upper & lower control arms. Anybody know anything about it? Is it worth getting these for a SB to BB conversion or will the non- BB arms suffice?

Are you sure that the difference isn't for drum and disc brakes. Not aware of heavy duty control arms.

Bob,
The note on the assembly manual says: " Wagon, Pick-up, LS3, LS5". I know the LS3=402, LS5=454 BB's. The p/n is 6263617-8 for the standard arm and 3990509-0 for the other one. I find it hard to believe the same arm is used for the truck. I'm asking as several past posts have indicated problems with the arms breaking or cracking and am wondering if it might be related to the added stress of the BB, not to mention 30+ year old steel. :confused: Just trying to get ready for the BB this summer, and I was planing on rebuilding the suspension since I have to replace the front springs anyway.

I would think the difference would be in the ball joints and/or the bushings, not the arm itself. The arms were pre-assembled with ball joints and bushings in place so they would have had different part numbers to tell them apart but that doesn't mean the arm unit itself is any different. And I don't believe the arms themselves are any different from application to application.

Rich,
I went ahead and looked up lower and upper ball joints - only one number for all SB & BB. I guess this wouldn't be the first time a factory manual is wrong,misleading, or vague. Thanks.

According to Modern Muscle catalog the 3990509,10 are listed as 64-72 except 70-72SB which have different numbers, (and noted to have the oval rear bushing) which would account for a different part numbers. (6263617,8 is listed as the 72 SB part). My 1975 Chevy parts book shows these that 6263617,8 were the latest replacement parts for all 64-72. So the rear oval bushing may be the only difference.

Rene

Tino,

The "Pick-Up" they refer to is the El Camino, not the light truck type pick-up which is why the parts are the same.

Rene,
That makes sense now. Thanks. :D

Dave,
That finally occured to me when I woke up this morning. graemlins/clonk.gif