Cast iron UCA versus aluminum UCA ball joint tapers

[iamdub]

I was given stock struts and upper control arms from a 2020 Silverado or Sierra that was lifted after only 6,000 miles. I really just wanted the struts to cannibalize for parts, but am now looking at swapping on the aluminum arms to have new OEM stuff, save a few lbs. and since @89Suburban called me out on my broken ball joint stud.

The arms appear to have the exact same critical dimensions as my OEM Tahoe arms. The ball joint seems to go into the stock knuckle about half way. Or maybe it is all the way? There appears to be plenty of threaded stud length with the BJ bottomed out in the knuckle, but it also looks to be a little longer than the OEM stud. I know there are some stud taper discrepancies between generations. A quick eyeballing shows the ball joints studs to be the same. Is the taper much different between the generations? I was unloading the parts and didn't have time to mic 'em.

I wanna say it was James @swathdiver discussing this at one time a while back.

 

[swathdiver]

Well, on our generation they list the stud sizes as 121 x 61 (cast iron) and 126 x 61 (cast aluminum). I reckon that that does mean the taper is different. Can't find the 2020s specs on the ACDelco website.

 

[jeremiahm]

I replaced my aluminum with cast iron (cost) and have not had any issues. Been running them for 10k miles.

 

[randeez]

Well, on our generation they list the stud sizes as 121 x 61 (cast iron) and 126 x 61 (cast aluminum). I reckon that that does mean the taper is different. Can't find the 2020s specs on the ACDelco website.

could also just mean the top mount is thicker on the aluminum and it carries the same taper further, making it wider?

I was given stock struts and upper control arms from a 2020 Silverado or Sierra that was lifted after only 6,000 miles. I really just wanted the struts to cannibalize for parts, but am now looking at swapping on the aluminum arms to have new OEM stuff, save a few lbs. and since @89Suburban called me out on my broken ball joint stud.

The arms appear to have the exact same critical dimensions as my OEM Tahoe arms. The ball joint seems to go into the stock knuckle about half way. Or maybe it is all the way? There appears to be plenty of threaded stud length with the BJ bottomed out in the knuckle, but it also looks to be a little longer than the OEM stud. I know there are some stud taper discrepancies between generations. A quick eyeballing shows the ball joints studs to be the same. Is the taper much different between the generations? I was unloading the parts and didn't have time to mic 'em.

I wanna say it was James @swathdiver discussing this at one time a while back.

i swapped 2015ish aluminum uca/lca/spindles for a while...the spindles are out cause of lift kit.
i always heard the ball joint and tie rod ends were different, tie rod ends i did have to order for a 2015 truck but they were the same thread to the steering rack link.
on the newer trucks parts are usually listed for stamped steel/aluminum arms or forged arms. so there are different variations for those also

 

[iamdub]

i swapped 2015ish aluminum uca/lca/spindles for a while...the spindles are out cause of lift kit.
i always heard the ball joint and tie rod ends were different, tie rod ends i did have to order for a 2015 truck but they were the same thread to the steering rack link.
on the newer trucks parts are usually listed for stamped steel/aluminum arms or forged arms. so there are different variations for those also

I recall you having the aluminum parts. I know there's a difference, but trying to find out what the difference is, in numbers. With my quick assembly yesterday, it looked like the BJ in the aluminum arm might have the same degree of taper, but longer stud. I'm not gonna buy a $100 reamer to run these arms. If I can confirm there is a difference that I'd need to address, I MIGHT see if I can borrow a reamer. Kinda don't wanna permanently mod my drop spindles for this. But kinda don't care. Especially if it won't cost me anything. Really, it's all more a "just cuz I have 'em" thing.

 

[iamdub]

Well, on our generation they list the stud sizes as 121 x 61 (cast iron) and 126 x 61 (cast aluminum). I reckon that that does mean the taper is different. Can't find the 2020s specs on the ACDelco website.

Thanks, James. I'll see if I can relate these numbers to anything. If I could ever be home from work at a decent time, I'd go take some measurements.