Drifting/pulling on highway - alignment issue?

[OSSGuy]

Hey all, I'm having an issue where the truck wants to pull to the side at higher speeds - at 60mph I need to keep a constant force on the wheel to keep it going straight. It doesn't always pull in the same direction, and might be pulling towards the lower side of the road (ie. on perfectly a flat road it might go straight), but I'm not sure yet.

I just got a set of 33's (285/70-17), installed SPC UCAs, and took it to a shop for an alignment. After the alignment I noticed the the ball joint in the left UCA wasn't seated properly (it's adjustable on the SPC UCAs), so I loosened it and use my digital angle gauge to adjust the camber and caster back to what the tech originally set it at. I was able to get the camber and caster to within 0.1 degree of where the shop set it at, but I didn't touch the tie rod or measure toe-in.

Would adjusting the caster and camber via the UCA also affect the toe-in? If so, could a misalignment on toe-in cause the pulling I'm experiencing?

For reference, here are the alignment specs from the shop (before I fixed the left UCA and re-adjusted the camber and caster):

Camber: L -0.3, R -0.2
Caster: L 5.1, R 5.2
Toe: L 0.03, R 0.04

 

[Hungryhawk]

Remember some roadways are designed for water to flow off to the right side/shoulder, and some to left.
So depending on roadway I usually get a little pull , mostly to right, sometimes to the left.
If your pulling strong to left or right it is surely an allignment issue.
Alligning is art and science. Some technicians do a great job. You can assist by making sure the caliper & wheel mating surfaces are smooth, clean and will fit together repeatedly the same with proper torque of lug nuts.

 

[OSSGuy]

Yeah, I'm thinking it's pulling to the side because the road isn't perfectly flat. I'm surprised by how much it's pulling, though. It's pulling a lot harder than before I replaced the UCAs and increased the caster. I know increasing caster is supposed to make the steering feel heavy, but I didn't realize it would also pull to the side harder.

I'm going to try reducing the caster back to the OE specs. I asked the alignment tech to use a high caster because I heard it would move the tire forward, but that's only true when you're adjusting the LCA. When you're adjusting the UCA, decreasing caster makes the tire go forward. This video does a great job of explaining how that works - https://www.youtube.com/watch?v=huMztKaHsUE

I'll try to update this post after I try a lower caster, but I'm moving in 2 weeks and might not have time to get to it for a while.