david85
Full Access Member
This one will be a long read. I held off on mentioning this little mod because I wasn't 100% sure how well it would work out in terms of longevity. Granted, my truck doesn't get used much anymore but it has been a couple years since I attempted this little hack and its still working great.
Ok, storytime...
My longest complaint with this truck was how poorly the steering would return to center when completing a turn. The problem was worse during a lane change at highway speed. Lane tracking was also quite a chore. There always seemed to be enough friction in the front end to prevent the engineered caster/camber dynamics from pulling the truck straight as was intended by designers.
This wasn't a problem in my F150 for a few reasons:
1. The F150 uses ball joints while the F250's in 1986 still used old school kingpins.
2. The F150 always had a pull to one side the likely masked any vagueness near center at light steering inputs.
3. Even though power steering was standard by 1986, F250s of 1980 vintage were still designed to work without power steering. This meant that caster angle was quite small, which reduces steering effort. Unfortunately it also meant less force available to pull the truck straight of its own accord(remember, caster actually lifts the vehicle slightly when the wheels are turned)
The results were quite tiring on long drives. Minor corrections for lane tracking at highway speeds often snagged in the steering friction only to pop loose unexpectedly (expansion joints, bridges, etc). So yes, bump steer was part of the problem. This caused over-corrections and even led me to believe there was excessive play in the front end. In time, I simply learned to deal with it by applying gentle input and waiting for the truck to respond. Watching my dad try to drive it on rare occasions only confirmed something was wrong (with the truck, not him).
At this point, you're probably thinking the kingpins weren't greased. Well I greased the living hell out of them before replacing them...then greased it up some more. The PO had also greased them liberally.
Having said that, the thrust bearings were shot when I got the truck. The sintered bronze bushing was all but chewed away and it was steel on steel bearing the load of the front half of the truck. Vertical play in the knuckle was about 1/8".
A complete kingpin set helped slightly but still didn't cure it. I gave up for a while and lived with it figuring I'd convert to 4wd eventually anyway.
New steering box. Yup, I even fooled myself into thinking that adjuster screw could fix it. Nope. This is almost NEVER worth messing with as I later found out.
Tie rod ends? Nope. It still wouldn't pull to center and I still had to steer the truck like an container ship on the highway.
Caster adjustable radius arm bushings? Nope, that made zero difference but they are still in there to this day.
By now I got pretty good at aligning this truck and everything checked out.
After a new set of tires, and having everything balanced nicely I found the problem only got worse. Later when one of the weights flew off and started shaking, it got better. In fact it felt like a whole new truck at 70 mph due to how well it would give feedback through the wheel and accept input for even the slightest lane tracking correction...so the issue definitely wasn't in the alignment. It was friction.
At this point I came to a realization.
The only thing left that could be causing the problem was the thrust bearing itself (the poorly balanced wheel was causing enough vertical vibration to loosen the front knuckles). Googling at the time confirmed that needle bearing conversion kits were available for older vintage trucks that came with kingpin style knuckles (mostly Chevy, of course). It turns out many big rigs also use needle bearings instead of bushings on their I-Beam front ends.
Naturally there wouldn't be anything for an 86 F250, so I started looking into making something up myself. I figured the main pin bushings weren't the problem and most of the friction would be eliminated at the thrust bushing.
Continued....
Ok, storytime...
My longest complaint with this truck was how poorly the steering would return to center when completing a turn. The problem was worse during a lane change at highway speed. Lane tracking was also quite a chore. There always seemed to be enough friction in the front end to prevent the engineered caster/camber dynamics from pulling the truck straight as was intended by designers.
This wasn't a problem in my F150 for a few reasons:
1. The F150 uses ball joints while the F250's in 1986 still used old school kingpins.
2. The F150 always had a pull to one side the likely masked any vagueness near center at light steering inputs.
3. Even though power steering was standard by 1986, F250s of 1980 vintage were still designed to work without power steering. This meant that caster angle was quite small, which reduces steering effort. Unfortunately it also meant less force available to pull the truck straight of its own accord(remember, caster actually lifts the vehicle slightly when the wheels are turned)
The results were quite tiring on long drives. Minor corrections for lane tracking at highway speeds often snagged in the steering friction only to pop loose unexpectedly (expansion joints, bridges, etc). So yes, bump steer was part of the problem. This caused over-corrections and even led me to believe there was excessive play in the front end. In time, I simply learned to deal with it by applying gentle input and waiting for the truck to respond. Watching my dad try to drive it on rare occasions only confirmed something was wrong (with the truck, not him).
At this point, you're probably thinking the kingpins weren't greased. Well I greased the living hell out of them before replacing them...then greased it up some more. The PO had also greased them liberally.
Having said that, the thrust bearings were shot when I got the truck. The sintered bronze bushing was all but chewed away and it was steel on steel bearing the load of the front half of the truck. Vertical play in the knuckle was about 1/8".
A complete kingpin set helped slightly but still didn't cure it. I gave up for a while and lived with it figuring I'd convert to 4wd eventually anyway.
New steering box. Yup, I even fooled myself into thinking that adjuster screw could fix it. Nope. This is almost NEVER worth messing with as I later found out.
Tie rod ends? Nope. It still wouldn't pull to center and I still had to steer the truck like an container ship on the highway.
Caster adjustable radius arm bushings? Nope, that made zero difference but they are still in there to this day.
By now I got pretty good at aligning this truck and everything checked out.
After a new set of tires, and having everything balanced nicely I found the problem only got worse. Later when one of the weights flew off and started shaking, it got better. In fact it felt like a whole new truck at 70 mph due to how well it would give feedback through the wheel and accept input for even the slightest lane tracking correction...so the issue definitely wasn't in the alignment. It was friction.
At this point I came to a realization.
The only thing left that could be causing the problem was the thrust bearing itself (the poorly balanced wheel was causing enough vertical vibration to loosen the front knuckles). Googling at the time confirmed that needle bearing conversion kits were available for older vintage trucks that came with kingpin style knuckles (mostly Chevy, of course). It turns out many big rigs also use needle bearings instead of bushings on their I-Beam front ends.
Naturally there wouldn't be anything for an 86 F250, so I started looking into making something up myself. I figured the main pin bushings weren't the problem and most of the friction would be eliminated at the thrust bushing.
Continued....
