Correct finish on upper control arm shafts

[Steve G.]

I am looking to determine what the correct finish was from factory for 1970 upper control arm shafts. I have two different types on my car, so I suspect one was changed. They both look identical, except one has a 'textured' surface that appears to be from a sand casting. The other is much smoother. Interestingly I was speaking with someone else that found the exact same thing on their car. A close up picture from his parts are in the attachment. The top shaft in picture is smooth. Bottom one is 'grainy'. Which is correct, the sand cast or smooth? thanks, Steve

[Joe L.]

Re: Correct finish on upper control arm shafts

I am looking to determine what the correct finish was from factory for 1970 upper control arm shafts. I have two different types on my car, so I suspect one was changed. They both look identical, except one has a 'textured' surface that appears to be from a sand casting. The other is much smoother. Interestingly I was speaking with someone else that found the exact same thing on their car. A close up picture from his parts are in the attachment. The top shaft in picture is smooth. Bottom one is 'grainy'. Which is correct, the sand cast or smooth? thanks, Steve

Steve-----


Neither shaft is a sand casting. The upper and lower shafts were both forgings. As I recall now, though, the upper shafts were shot-peened. That's what gave them the non-smooth surface texture. So, I'd say IF one of yours has been replaced, it's the one with the smooth surface texture. I don't know that all of these were shot-peened, though. So, it may be that both are original to the car.

[Alan S.]

Re: Correct finish on upper control arm shafts

Hi Steve,
I have a similar situation on the cross shafts on my 71, 6589. Both are original to the car with 44k miles. The passenger side forging is very smooth, while the driver's side forging has a very even texture. Neither side was very rusty at all, so I don't think the surface was affected by rust.
If you'd like a picture let me know and I'll gladly take a couple.
Regards,
Alan

[Steve G.]

Re: Correct finish on upper control arm shafts

Thanks Joe. It makes sense that these were shot peened. I assume that was done to strengthen the shaft?

Alan, yes - please do email pictures of your originals - thanks! Steve

[Steve G.]

Re: Correct finish on upper control arm shafts

I was looking to buy an upper control arm shaft with shot peened surface so I could have a matched set. I found someone that has one for sale, though I am not sure this one is correct and would appreciate opinions. See attached pictures from a rusty car! Joe, you mentioned they were forged, and some were followed by shot peening operation. These pictures show a textured surface (though they are very rusted, so I can't tell if the texture is due to peening and rust, or rust only) but they also show some sort of a line along the shaft that I assumed to indicate a casting mark. Can you tell from these pictures if they are 'correct'? And if so, could I bead blast and clear coat (semi gloss) these or are they too far gone and I would end up having to deal with the rust again in near future? Steve

[Terry M.]

Re: Correct finish on upper control arm shafts

I
These pictures show a textured surface (though they are very rusted, so I can't tell if the texture is due to peening and rust, or rust only) but they also show some sort of a line along the shaft that I assumed to indicate a casting mark. Steve

Steve,

That mark is a part of the forging operation. The hot metal is "squished" (note that is a highly technical term ) between two dies. The excess metal is squeezed out. The next operation is to trim off that excess metal in another die -- the edges of which are designed to cut off that excess metal. The result is that line.

Yes a casting can have a similar line, but the casting line (called a parting line) will be smaller and generally not show the cut edges from the t******* operation.

[Chuck S.]

Re: Correct finish on upper control arm shafts

...These pictures show a textured surface (though they are very rusted, so I can't tell if the texture is due to peening and rust, or rust only)...

Unless your other upper shaft looks like that one, I would keep looking...in my opinion, most of that is corrosion (aka rust) and not shot peening.

Shot peening compresses the metal near the surface of the part, and puts the surface of the part into compression which helps to prevent crack initiation. If you can postpone crack initiation, you have a much stronger part that will withstand higher loads for more loading cycles.

[Joe L.]

Re: Correct finish on upper control arm shafts

Unless your other upper shaft looks like that one, I would keep looking...in my opinion, most of that is corrosion (aka rust) and not shot peening.

Chuck and Steve----

I agree. Most of the "textured" surface here was induced by corrosion, not shot-peening. In fact, the corrosion has "obliterated" the shot-peened surface.