My brother has a '94 Bronco, and the right side tire is shaking as he drives it. Under some conditions, the tire can make contact with the bumper, but at other times it will clear the bumper by about a quarter inch. (The tires are oversize, so the tight fit is expected, but the left side tire never touches the bumper whereas the right side tire can touch when the stars align just so.)
I think the bushings are toast, but I've not actually done this job before so I wanted to get a second opinion.
Would somebody tell me what I can expect for parts cost, or for paying a reasonable mechanic to do the job?
I think you are refering to radius arm bushings (insulators) and if that's the case I don't think what you described would be caused by worn bushings. First thing I'd check is the wheel bearings and make sure they are not loose. Also get the tires rebalanced.
If the Bronco radius arm bushings are like the Explorer and this is the first time it's been done you may need to drill out the rivets that hold the plate that the bushings are attached to and replace the rivets with good machine screws with lockwashers and nuts. This is generally considered easier than disassembling the front suspension. The parts (bushings) cost around $20-30 maybe. If you pay someone to do it I'd guess maybe $80-100. You need the correct sized socket (1/2" drive) and a long breaker bar to get them off. If you Google "radial arm bushings" or "radius arm insulators" you should find several posts.
If the bushings are worn you will probably hear a "clunk" when coming to a stop. The bushings usually look worn. With oversized tires it seems fairly standard to torque down the wheel bearings more than what the specs say.
Is the Radius Arm the bar that ties the outboard end of the I-Beam (is it still an I-Beam in the '94 F Series 4WD?) to the frame at a point basically under the passenger side footwell?
The truck makes no noises when coming to a stop, but does make a clunk when you first begin to get underway after completing a full stop. There is a tech bulletin that states this particular noise comes from the drive shaft slip-joint, and the noise has been in the truck for a very long time, and the tire rub is new.
I believe that what is happening is on a Reverse manuver, the tire moves forward when the truck stops, and this allows the tire to rub the bumper. I've not studied this theory very much, but that's my instinct. If the tire can move fore and aft against the trailing-end of the Radius Arm where it fits into the bushing, and the bushing has finally broken enough to let the wheel flop around while driving, then I think we're onto something.
I can visualize that problem and the repair action needed.
I was thinking when I initially posted that the front suspension bushings where the I-Beams tie to the frame rails were going to be my problem. This truck does not have an A-Arm set up on the front end. It gets a beam for the left side tire that attaches to the right side frame rail, and another beam for the right side tire that attaches to the left side frame rail. There is some manner of stabalizer stuff that keeps all of this stuffl lined up, and I was expecting a report on the repairs needed here. I had not considered the radius arms.
The most likely problem is (are) the radius arm bushings. The one on the right side is the one that usually fails since it is next to the muffler and gets beaten to hell and back there on the rought side of the road anyway. Another poster suggested drilling the rivits in the brackets that fasten the brackets to the frame. Use bolts to reattach. You will need some patience and a damn good drill with a carbide bit to do this. Around that vintage, Ford even had a TSB somewhre along there as a fix for a pop noise in the frame under some conditions. If you go that route, make damn sure you get the proper bolt hardward to hold it together. Those bolts have to be tight and good enough to stay that way.
If you do have a pop in the frame, you may want to inspect the area around the steering gearbox for cracks. Some did that. There was a reinforcing kit installed to repair this. Sometimes, the gearbox bolts were simply loose and all was well after tightening.
Another prime area for poping and crackling on them is the front crossmember rivits. If there is any indication this is the proble, the only solution is drilling out the rivits and replacing them with bolts. Again, these are special bolts that could be had in a kit at one time. If you buy other than the kit, make sure they are SAE grade 8 nuts, bolts and washers. Again, they will need to be tight. Check the torque specs for the bolts and put it to it.
Every one I have ever replaced the bushings on, I found it just as easy to put it up on the stands and drag out the air tools. Disconnect the shock and lower the axle with a jack. Loosen the bolt that attaches the radius arm to the axle so it can move. IT is also recommended to remove the upper spring clip to the frame so the spring doesn't interfer with pulling the axle forward. Remove the large nut at the rear of the radius arm and pull the axle forward out of the frame bracket. A come-a-long may be handy for this if you have the truck so it can't move and something to tie onto. A long pry bar can also be used to move the axle forward if you have a helper. Install new bushings and reverse the disassembly to put it back together. Tighten the nut on the rear of the radius arm befor the one on the front to make sure it is not in a bind. You will know when they are tight enough when your 1/2" impact can't go any more. The washer on the rear of the arm will bottom against eh shoulder of the arm. I recommend you spend a couple of extra bucks and install the urathane bushings. It helps the overall handling of the truck and correct a couple of nasty traits like pulling ir darting when you apply the brakes or hit a rut in the road surface.
For you drive line thump, you need to pull the drive shaft and lube the splines with a good EP grease. That may only silence it for a while before it returns. Then you have to decide whether you want to repeat the lube process every so often or replace the front yoke. Yoke replacement is usually a permanent fix if it is installed with a good EP grease. Some yokes come with a zerk fitting to facilitate periodic lube but, you have to be careful not to overdo it with an automatic trans. Keep in mind the U joint has to be disassembled to replace the yoke. This would be a good time to replace U joints if they have some miles on them. If you have never done a U joint replacement, you would probably be ahead of the game to pay the local driveline shop to do it. An unbalanced drive shaft can loosen your fillings. Note: this problem does not occur since the driveline is not loaded when stopped unless you are a screwball riding the clutch.
All this sounds like a lot. Once you get started with the right tools, you should be able to knock it out in an afternoon if you pace yourself on the adult refreshments.
A pretty easy job in the grand scheme of things. The bushings were toast, but new ones did not repair the problem. We're looking at a balance problem, but the tires were balanced earlier in the week with no change in the symptom set.
My brother drove on the freeway, and I went in a different car to see if anything was shaking. We switched drivers, and as I drove his Bronco at
70-ish, the coins in the ashtray were about to jump out, but the tires had no movement that could be seen from the chase car. There was slight movement of the right front tire that could be coming from the shock -- but the shocks are Bilsteins and haven't many miles.
The right tire still can move fore and aft enough to strike the bumper. The tire does not always hit the bumper, it only hits it after backing up and stopping. When going forward, the tire does not strike the bumper, but in Reverse it does. I would have thunk replacing the radius arm bushings would have gotten this under control. The bushings that came out were clearly worn well beyond the service life, but new bushings did not fix the problem.
My brother just got back from the tire store, and the right front tire was out of balance by 13 ounces. Three ounces shy of a full pound! I'm pretty sure this is significant.
If the tire store had taken care of this earlier in the week, we wouldn't have been busting knuckles all day today.
I didn't see if you said you checked your wheel bearing (spline) nuts for tightness. I installed Warn manual hubs on my '91 Explorer and rather suddenly the brakes were going screwy and making strange sounds. It turned out that the spline nut that came with my new hubs was cracked and became loose. The only thing it damaged was the spline washer ($21 from Ford!!!) and Warn sent me a new nut and told me to torque the nuts according to specs, then back off as recommended, and THEN tighten it back down to where it "feels" right. This may not seem like proper procedure but it seems to have worked. I also put a couple of dabs of high-temp silicone on the nuts to help hold them in place (as recommended by Warn). The reason I'm telling you this is because my brakes were so severely effected and it was not clear just why so it might cause other strange problems too.
I've never done ball joints and I don't know what the symptoms are but some Broncos have them so you might want to look that up too.
I had some off brand tires on the front of my '93 F-150; it had a severe shake and the LF shock was completely worn out when I bought the truck. I replaced the shocks and had the front tires balanced and it was much better but still the steering wheel would move about 1/2" at highway speed. A new set of Michelins fixed it right up. I'd taken the truck to a different shop than the one that originally balanced the tires and asked them to let me know if I really needed new front tires (I knew I needed new rears; they were old Michelins that were pretty decently weather checked) and they told me that they simply could not balance them any better than they had been. Not sure why that would be unless someone had used "fix a flat" in them but now it is rock solid stable, at least up to about 75 MPH (hard to get going any faster with a 300 and not sure I want to...)
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