Impala control arms

0xDEADBEEF said:

Is the lower ball joint moved? Could be a problem, or even an improvement.

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You’d have to move both upper and lower, I’d think, to keep the same geometry…and I’ve only looked at a 94 impala

History: I’m so damn glad this has generated interest. Ok, I’m 100% new to the OBS and this is my first frame off, so yep, I’ve made some mistakes. So, I don’t want to invest in more wheels but I’ve noticed a lot of OBS trucks with damn tight wheel clearance. The truck I really liked was a gold OBS that “Street Trucks” dropped 4/6 and actually specified the exact tire/wheel package used and it looked damn good BUT they never even hinted at a tire clearance issue nor rolling the inner edge of the fender, nada.

Soooo……I’m looking at how to narrow the front economically. I’ve just received a new 94 impala UCA to be used as a comparison. No real info yet, but for sure it’s much more narrow. I can also see that I’ll need to knock out the impala cross shaft (?) that allows mounting the arm to the impala…..there’s going to be some challenges for sure….more later, I promise, I need to set up an accurate “jig” to ensure consistent measurements.

Yesterday I received a new UCA, measured from ball joint to mounting centerline, there is one inch less on the impala. The ball joint isn’t in the same position as the OBS which means if used it would change the center of the wheel position in the fender well. Although not exact yet, it seems like it would be way too much, about 1-1/4” forward. I also think the height of the ball joint mounting surface on the impala is 1” higher than the OBS. YES…some issues and I’ve still gotta try the lowers. Before commenting on caster, etc., I really need to get a full set from either an impala or an Astro. I know that I must replace impala bushing with OBS and that may allow me to solve wheel position error. This week I’ll get the Astro front assembly.

!! Caster is set by the centerline offset of the upper and lower ball joints , so a difference in ball joint mounting angle will not affect caster.

I wonder how these would work on a 3500 if you can solve the wheel position issue.

It would be cool if there was an off the shelf GM part that we could use, but it might not exist.

I've been doing some research on Mustang II suspension lately. SPEC makes an UCA where both arms are a turnbuckle. I dunno, might be useful to make an upper and lower that way so you can get everything exactly where you want it and then make a jig from that so that build your own control arms.

Even if the Impala arms fit, should they be used on the GMT400... do they have the strength?

"Your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should." - Jurassic Park, 1993

1998_K1500_Sub said:

Even if the Impala arms fit, should they be used on the GMT400... do they have the strength?

"Your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should." - Jurassic Park, 1993

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Depends on what you're gonna use the truck for....mine is a toy.

1998_K1500_Sub said:

Even if the Impala arms fit, should they be used on the GMT400... do they have the strength?

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Would have to see comparison pictures. Like what was stated above for a street truck they would probably be just fine. Impalas or the caprice sedans were heavy cars and were even rated to tow decent weights compared to modern cars. May need to notch your a-arm mounting brackets to get it aligned. I may be surprised but I doubt the UCA and LCA mounting geometry is the same between the two vehicles.

Hats off to you for trying and experimenting with these parts.

I checked the ratings on a 1996 Roadmaster Estate wagon owned by a friend, here's the door sticker showing GVWR etc. (pictured below). They're not quite those of a C1500 (~6100# GVWR from what I can find), but for an unloaded C1500... OK. I doubt the OP's going to be carrying 1500# in the bed or pulling a large trailer... @618 Syndicate's and @TreeGeared's points noted.

I asked my friend what his Roadmaster weighed, but he's never scaled it. He estimated 4800#. My K1500 Suburban scaled at close to 6000#, so a C1500 P/U has to be somewhere in between.

Brakes on the front are comparable diameter b/t the Roadmaster and C1500 (and likely more heat capacity in the C1500 due to thickness):

Roadmaster front rotor
Nominal thickness 1.035
OD 11.858

C1500 front rotor
Nominal thickness 1.285
OD 11.610

TreeGeared said:

Hats off to you for trying and experimenting with these parts.

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Amen to that.

0xDEADBEEF said:

I've been doing some research on Mustang II suspension lately. SPEC makes an UCA where both arms are a turnbuckle. I dunno, might be useful to make an upper and lower that way so you can get everything exactly where you want it and then make a jig from that so that build your own control arms.

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Smiley's Racing sells all the parts to make your own upper control arm from adjustable pieces. This is my Sunbeam Alpine crossmember mocked up with Mustang II parts on the driver's side. Six years later and it's still sitting in pieces on the shop floor...