Thanks for sharing, great video
With the coil spring suspension in the rear if any of the rear link bushings are worn it could cause the thrust angle to increase
I'm surprised they didn't check the rear angles,
The thrust angle has to be known to set the front toe correctly,

Neal

 

Legerwn,

They did check the rear spec during each alignment, it's on the bottom half of the sheet. We discussed it being a possible cause and the tech said he didn't believe it would cause this issue.

Also, I did check the rear control arm and track bar bushings with a pry bar and they're all good.

I've tested everything I can think of at this point and can find nothing wrong. I think the alignment was not done correctly but it's odd that it's the same issue after all the new parts and work.... Maybe because the caster is overall low even though cross caster is in spec?

I'll try to find a shop that's experienced in alignments on the gmt 800 trucks. More than half the shops I called weren't even willing to align this truck, or in the recent past my 68 Camaro because it's "too difficult" even though double wishbone suspension is ancient... Not enough experienced techs I suppose...​​​​

 

Did you rotate all 4 tires straight side to side to see if pull changes direction?

 

Yes I have, it made no difference unfortunately.

​​​​

 

Find a shop that can perform an alignment closer to specs...
Here's the final specs you want:

Camber Left & Right>>> 0.00°-+0.25° (positive matching)
Caster Left>>> 4.25° Caster Right>>> 4.75°(offset for road crown)
Toe Left & Right>>>+0.10° (positive matching)

 

I just looked at the after rear specs: the RR toe setting is making right turns!

 

 

They don't setup the machine to measure rear toe because they're lazy. I do agree It could be a thrust angle issue although unlikely.

Where are you located? I wanna look at it. I'm about an hour north of Atlanta. I bet I could figure it out. I have basic alignment tools for these trucks. The front suspension geometry is trickier than people think. It could be an issue with dynamic toe or camber based on how the suspension is loaded under driving conditions. if you look at your alignment sheet, notice how your left toe is positive and your right toe is negative in the rear? If the machine is reading that but reading your front toe as straight then there's no way that truck's gonna go straight down the road and there's no way the front toe is correctly centered. That'll do some weird stuff as the toe changes throughout your steering angle.

Might be worth doing a once over of all your components. New doesn't always mean good. And every alignment tech I've ever met has been a pretty damn good liar. They'd rather hit the head on the tire with a hammer than adjust a tie rod or camber.

 

Thanks for the specs and videos, those have been helpful. The rear end being the issue would make sense as the pull persists after all the new parts.

Gavin,
That's extremely nice of you to offer. I'm in Nashville so a good distance from you unfortunately.

I see what you're saying, basically the front may need to be adjusted to compensate for the rear end being slightly out, correct? Would add up as the front end alignment "correct" but the rear is off.
​​I could buy adjustable rear control arms and track bar but it's quite expensive. Rear control arm bushings are all tight and I see no evidence or record of the truck being in an accident.

I've gone over everything I've done at least 3 times now honestly, this has been driving me crazy lol. Ha, and you're right on that last part, with the guys at the first location arguing with me about it being "impossible" to adjust. Makes no sense as there's plenty of adjustment available.... They didn't even touch the rear camber bolt the first time. I think lazy techs that didn't like me calling them out. 2nd shop at least tried...

 

What I think has possibly happened is the rear is actually straight but the truck is crooked on the rack if that makes sense. Like if someone doesn't center the steering wheel, the rack may read that it's steering straight ahead, but its actually off left or right. So what I'm saying is the rear toe is actually 0 or close to 0 but however the rack is reading center is not straight ahead to the vehicle. So then when they set front toe its not actually steering straight ahead. I dont know if any of that made sense or has any standing. I have never used a machine to align a vehicle ever.