I am working on a family members car, she is preparing for a cross-country move in her very cool partially restored 85 Bronco. The truck tracks poorly in a straight line. However, it does not pull to either side, cornering is fine and straight line braking is excellent. The wandering is dangerous and unpredictable at highway speeds. A mechanic has changed all sub-par rod ends and the radius arm bushings. The Bronco has been aligned several times and has had caster correctors added with no improvement. With all that work and no improvement. I have been trying to help. The movement of the drag link, pitman arm and steering linkages all move in time with steering wheel input. I just changed the power steering gear and I have had only imaginary improvement. The rag joint looks good, but we are going to replace it as well like everything else. Please help as we are tired of throwing parts at it. She thinks it might be in the column, I think mechanic put Bronco 2 radius arm bushings on, and the mechanic thinks she needs a new steering stabilizer “maybe 2”. By the way the truck is a 4x4 rides on new 33" all terrain / mud tires and the truck is not lifted there are no clearance issues and we have also replaced hubs and wheel bearings. Thank you in advance I appreciate the help as we are already concerned for her safety as she is a young female driving cross-country alone.
The truck will not track well on those tires. Go back to the original 215/75x15s (or 235/75x15s) in an all season tread and your tracking should improve dramatically.
Ford Broncos were notorious for their poor handling at highway speeds. The 4x4 pickups weren’t much better. I have done a great deal of experimenting with the 1st generation Broncos and the several linkage systems that Ford put on them. The 85 Bronco has one of the least friendly designs and my best success with that setup was to increase the toe-in to 1/4 inch. I will suggest that you get a ‘seasoned’ front end man’s opinion regarding experimenting with adjustments beyond specification and my feelings won’t be hurt if he laughs at my suggestion. Also, I agree that the standard size tires are a must for sustained highway driving.
Especially 33 inchers with all-terraine tread.
ALSO, are the wheels original equipment? Many after market wheels don’t match the original and often they totally destroy the front end geometry by moving the tire outward, causing all manner of grief.
Every little imperfection in the road will make the truck wander with these tires. It also puts extra stress on all the steering and suspension parts when you have tires that big. It can be really scary if you hit some standing water with these tires. A grooved road or bridge with a metal grate will make it seem like it has a mind of its own. I’d put some smaller tires on it. Is it driven off-road enough to even warrant the big tires?
Switch back to OEM wheels and standard “road” tires for the cross country trip. If she loves the 33" tires and custom wheels she can load them on the roof or ship them cross country. The truck is unsafe at interstate highway speeds with “off road” tires.
All the work you are doing won’t “change the spots on the leopard”. The truck had marignal handling to begin with, and the custom wheels and oversize tires just make a bad handling vehicle worse at highway speeds.
Or, she can stay off the interstates and drive cross country at about 45 mph on the current tires and wheels.
As long as we’re changing parts, how about changing the idler arm? If the idler arm can move up and down, there can be sudden steering problems.