How much to change caster (or others) to fix pull to the right? 1994 XLT 4wd 4.0

[Dwalk51]

I've had my 94 4.0 XLT 4x4 aligned EIGHT times by Firestone/Bridgestone and the truck keeps pulling to the right. I showed them the tech article here and they were skeptical, saying there was no way to know.

I installed dual-adjustable camber/caster bushings after the first alignment attempt and we've been going in circles trying to get this thing aligned. It continues to pull to the right pretty hard. They've agreed to re-align it with a caster differential to try to correct the pull to the right, but are telling me that I need to tell them how much to change the caster to try to fix it. Any ideas what # we should be shooting for here? I'm beyond frustrated that they keep telling me the truck is driving straight only to pick it up and find that it is definitely NOT driving straight.

Video of the pull to the right:

Latest alignment:

 

[Curious Hound]

By those numbers, it should be driving straight. I'm curious why the caster isn't in spec on either side. But I also think caster is one of the least important specs in the alignment.

A pull to one side could be caused by other things - brakes (bad caliper or hose) wheel bearings loose or bad tie rod ends/ball joints that allow things to move out of adjustment as you drive, and even tire problems.

When I do my alignments, I concentrate on camber and toe and just give it whatever caster I can with the available amount of adjustment. I have no way of measuring all those angles. I just do it with a tape measure and string and test drives. I mean, I actually do have a digital angle measuring thingy. But my driveway isn't level enough of flat enough for me to go be such measurements.

Also, most roads are crowned. So you are constantly driving on a slope toward the right side. So it is normal to have a slight amount of pull to the right. Just dont ask me to specifically define "slight amount".

 

[19Walt93]

Step number 1 is to find a qualified alignment tech who will adjust everything to the prefered spec. The camber is "in the green" but that isn't good enough and the caster is out of the ball park. The negative camber on that sheet will wear the inside edges off the tires. Our roads are crowned so we always used a .5 degree caster split to offset it. Apparently Michigan doesn't crown their roads so we had to realign the first 6 months of Explorers because they all pulled right. A properly aligned vehicle in NH will have a slight right drift in the right lane on the highway and a slight left drift in the left lane due to road crown.

 

[4x4junkie]

I see Camber is whats 'out of the ballpark' (in the red), Caster is green.
IME the caster split needed on these trucks is usually around 0.5-1° or so, pass-side being higher (you have 0.2°).
Given the amount of drift I see in that video, (just based on my own experience) I'm thinking subtract 0.7-0.8° caster on the driver side (or add that amount to the pass-side) should get you pretty close.

The camber can be corrected either at the bushings, or you can also do it by putting a washer or two under each of your coil spring seats (giving you about a ½" suspension boost at the same time). If you use washers, do it before you try aligning it again.

 

[Dwalk51]

I just redid all the brakes - fresh drums and pads on the rear, new rotors and pads on the front, and new wheel bearings on the front.

That tech article with the washers is super helpful, I may do that.

Appreciate all the feedback. I will ask them to aim for ~0.7* subtraction from driver (or add to passenger side). This whole thing has been a PITA trying to find a tech who is willing to take the time to do it. Firestone/Bridgestone keeps telling me they've got some old-school tech at another location who will be able to solve it and then nothing changes when I pick it up. Crazy.

 

[rumblecloud]

I'm like the Hound in that I use a tape measure and string, then test drive till it's close - watch for tire wear.
I installed adjustable bushings like you and also did a washer lift. There is no way an alignment shop would figure mine out

Walt and Junkie know what they're talking about though. Good luck with it.

 

[Dwalk51]

By those numbers, it should be driving straight. I'm curious why the caster isn't in spec on either side. But I also think caster is one of the least important specs in the alignment.

A pull to one side could be caused by other things - brakes (bad caliper or hose) wheel bearings loose or bad tie rod ends/ball joints that allow things to move out of adjustment as you drive, and even tire problems.

When I do my alignments, I concentrate on camber and toe and just give it whatever caster I can with the available amount of adjustment. I have no way of measuring all those angles. I just do it with a tape measure and string and test drives. I mean, I actually do have a digital angle measuring thingy. But my driveway isn't level enough of flat enough for me to go be such measurements.

That's good to know that it should be driving straight. I'm going to do rear wheel bearings next to see if that helps. All brakes and front wheel bearings should be good to go. The techs told me that none of the bushings/components are worn to the point of needing to be replaced, but I wouldn't be surprised if that's not true.

 

[Curious Hound]

I'm like the Hound in that I use a tape measure and string, then test drive till it's close - watch for tire wear.
I installed adjustable bushings like you and also did a washer lift. There is no way an alignment shop would figure mine out

Walt and Junkie know what they're talking about though. Good luck with it.

Junkie's tech article, in addition to just "playing with it" is what taught me how. There was a shop about 45 minutes from here that had a guy who really knew what he was doing. But he retired. I'm not going to pay somebody to figure it out.

 

[Dwalk51]

Ha! I thought paying for the alignment would save me time. Now I’m not so sure! I may have to align it myself in the end anyway

 

[rumblecloud]

Ha! I thought paying for the alignment would save me time. Now I’m not so sure! I may have to align it myself in the end anyway

It's kinda fun...if you're not that kinda thing.

 

[lowspeedpursuit]

Why did they set your camber out-of-spec negative? Even with fixed bushings, your alignment choices for the correct caster would be to add or subtract however much corresponding camber.

In before it turns out to be one of those "alignment" shops that advertises "full 4x4 alignment" but doesn't actually measure all 3 values, and the caster numbers on the printout are just placeholders.

These guys are "making it right", right? You're not still paying them for each of the 8 tries?

 

[4x4junkie]

If you want to try DIY, then here's what you need (scroll about halfway down):

Steering Tech - Discussing TTB Steering and Alignment - The Ranger Station

How it’s supposed to work (and why it often doesn’t work like so) Steering continues to be one of the most overlooked, often misunderstood pitfalls on these suspensions, so I felt this subject deserves it’s very own page. As many … Continued

www.therangerstation.com