Whenever my 1978 F-100 hits a rough part of the road it jerks violently from side to side. (I almost swung into the side of a semi's trailer today!)

What do I need to replace or fix?

Thanks,
CB3

 

Anything that moves under the truck when you turn the steering wheel.

Seriously, all that stuff needs to be checked. Your frame and suspension mounts need to be checked. Your steering box to frame mounting needs to be checked.

And, you should park it until you can get a handle on it. Stuff like this does not get better or stay the same. A crack can get bigger, and with it your bump steer can turn into death wobble or worse yet, it can turn you into oncoming traffic.

I had a '65 Mustang with "guardrail seeking brakes". I took it in for an alignment---"We can't align this thing, look at this..." Cracks, breaks, it's a wonder I didn't eat it driving it to the shop.

Why did my car have all those problems? Well, it hadn't been repaired properly after I hit another vehicle that had a suspension failure in front of me on the freeway and just made a left turn into my lane.

So yes, over reaction answer, but I think you've got the picture, good luck with it.

 

X2 on get under it and insp EVERYTHING THAT MOVES when being driven and or moves with the steering wheel. Also ck play..IE being worn out..radius arm bushings, shocks, wheel bearings loose, tie rod ends shot. Pit man arm nut tight? Steering box tight to the frame and with no cracks?

X100 on all the other stuff mentioned above. Steering shaft rag joint. Steering box internally might be shot. Are you tires worn evenly, have you ever had a front end alignment done?

A number worn parts can multiply into lots of play. Busted front coil spring, have it running and in park with the e brake set and have a buddy set in it and turn the steering wheel back and forth like a 1" or so.

Eye ball, get a hand on it and see what has slop or play. If you were on the brakes I would say bad rotor and or sticking caliper.

 

High probability the kingpins/kingpin bushings are worn out and the radius arm bushings are probably shot.

All of the front suspension needs to be gone over and all the suspension and consumable steering parts previously mentioned need to be replaced.

No need to get an alignment, if all these parts are worn, until AFTER they are rebuilt. An alignment now won't correct for worn out suspension and steering parts.

 

Call me crazy ...... I would do a full visual and hands-on inspection of the suspension and steering systems and look for cracked bushings, loose/worn tie rods, loose hardware, wobble in the kingpins and wheel bearings, and also look for cracked/broken components, etc.

Then I would make a list of all the parts to replace the system because if there is one bad part than the other components are likely right behind it. Then maybe act like a savvy shopper to stretch my dollar and see who sells quality branded parts at good price points so the parts fit and work as advertised.

My first question would not have been to log in to ask such an open ended question since I should know my truck better than anybody online. I mean, it's my truck, right? Rather, I would have learned how the truck's systems work so I can ask more direct and specific questions. However, I think there would be FTE members who can provide input although the way it is stated might be really weird - if not outright strange.

I'm sure others will chime in with the right answer really soon.

 

A way I like to check for steering issues is to run the car/truck up on ramps. Weight is on the front tires and there is plenty of room to slide under. Get a helper to turn the wheel back and forth and check for slop in all the joints and bushings. You can check visually and also by feel... put a hand over each joint and see if there is "clicking" or you can feel excess movement.

Also a good way to check for steering box movement and visually inspect for cracks.

 

The 3 aspects of a vehicles alignment are toe-in(or out),camber,caster.If the caster is off then it will cause a vehicle to "duck" and "dive", sometimes very unpredictably. So, IF this might be the case then WHY is the alignment off? A person needs to go thru' all of the above postings to find the reason(s) and cure. Good Luck. Gary

 

Thanks to all of you for the suggestions as to what to do to find my problem.
CB3

 

Feel free to follow the latter part of my build here where I repair or replace just about everything involved with suspension and steering. I started out to replace only the axle pivot bushings and the radius arm bushings but found much more to do once I got into it. I am currently in the process of trying to stop the power steering unit from leaking past the sector shaft seals. You never know what one of the POs has done or un-done or what 40+ years of use has left you with so "trust but verify."
Start with a thorough clean-up – Gunk (or equivalent such as kerosene) and a putty knife or other scraper plus a pressure washer so that you can actually see past the grease and dirt. I got carried away painting everything in sight but you don't need to go that far.
BTW, I was puzzled not to see much in the way of suspension adjustability. Reading up on this in the Ford Truck Shop Manual revealed that toe-in is the only available adjustment. Caster and camber, apparently, are pre-set so that makes those bushings even more important.

 

Thank you, flowney. You were a great help!

CB3