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Doug118

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any idea what the pinion angle SHOULD be?

I didn’t read through the first few pages but do you have the trailing arm relocation brackets already? There shouldn’t be a pinion angle issue. I would measure it now and make it exactly the same when you change the arms

I personally would remove both bottom arms, measure them, then make the Spohn ones 1/2” longer. Then do the same for the top
 
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KidWgn

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I didn’t read through the first few pages but do you have the trailing arm relocation brackets already? There shouldn’t be a pinion angle issue. I would measure it now and make it exactly the same when you change the arms

I personally would remove both bottom arms, measure them, then make the Spohn ones 1/2” longer. Then do the same for the top
I do. I also hate them. I think it’s a poor design that should be welded into place, not secured with a single bolt running vertically.

I think I’m going to try to recreate the correct angle without using those brackets.
 

iamdub

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It happens between 65-75 mph. The intensity is sporadic, but it FEELS like a wheel out of balance. It's a left to right shake, for sure, not a "bounce". Doesn't happen at all during low speeds or during braking.

I was trying to rule out a bent axle flange with the braking questioning. So, different wheels and rotated, etc. but the shake remains in the rear. Hmm...


Very great idea on making the jig for repeatability. I'm a machinist by trade, so I have all kinds of handy measuring tools; I'll probably just measure them with a 24" ruler down to the hundredth. I wish I had access to the machines at home, that I do at work. I work for Boeing, so it's pretty frowned upon to bring in "home projects" lol.

Shiiiit... I'm preaching to the choir. Being a machinist, you already have a handle on it with basic tools and a trained eye. I might be needing the assistance of a machinist when I get to building my rear upper control arms. The bushing sleeves are SAE but I wanna use the stock bolts, which are metric. I have options, but having custom sleeves made with a metric ID and SAE OD would be the bee's nuts.
 

Doug118

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I do. I also hate them. I think it’s a poor design that should be welded into place, not secured with a single bolt running vertically.

I think I’m going to try to recreate the correct angle without using those brackets.

I ended up welding mine after that single bolt came loose
 

iamdub

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any idea what the pinion angle SHOULD be?
Well, Mr. Boeing Machinist, did you not measure all of these critical points BEFORE you started hacking away? redass.gif


I have mine recorded somewhere. Before I dropped it, I measured all the corners and stuck a magnetic protractor to the driveshaft, rear pinion snout, etc.

I've made no measurements after the drop, assuming the LCA relocators accounted for this. Having no noises or issues otherwise with the original 225K-mile U-joints in excess of 145 mph, I assume it's fine.

Talk sweet to me or just ask me repeatedly and I'll eventually get you the numbers I have so you can have something for reference. GM is known to have comparatively loose manufacturing tolerances in the larger systems where they're less critical. So, my numbers may not be so applicable to yours. I'd say they would be plenty close enough to be a start.
 

iamdub

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I do. I also hate them. I think it’s a poor design that should be welded into place, not secured with a single bolt running vertically.

I think I’m going to try to recreate the correct angle without using those brackets.

Mine have been in place for about 30K miles. Never touched 'em after installation. I'm not gentle on my suspension. And mine have two vertical bolts plus the two horizontal ones that go through the original arm mounting point.

This reminds me that my Tahoe Twin buddy with the same drop components has had his right side bolts work loose at least twice.
 
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