I have a 1975 f250 highboy the front end of the truck of course has the closed knuckle Dana 44 HD with power assisted steering. When going 50-75 the the front end shakes violently. I've checked brake shoes and the drums and they all checked out to be good no warps in the drums. Alignment is perfect I can literally let go of the wheel and it won't pull to the right or the left. I'm selling the truck and the buyer noticed the shaking so I'm trying to fix it for him. If anyone has advice or has fixed this problem I really need to know what you did!

 

Do you have stock size tires? My '77 highboy shakes pretty good at those speeds - it never did it with 33's but when I put the 35's on it does it. It's not a warped rotor shake, it's more of a death wobble but only while the brake pedal is pressed. I'm beginning to wonder if it's the steering dampener. It's still the stock one and I highly doubt it's doing anything anymore at this point. I've been saying I'm going to replace it and see if that helps. If that doesn't, I'm going to completely restore the entire braking system, needs it anyway. Everything on the braking system is original, except for the front brake pads and the master cylinder. Rotors, drums, shoes, wheel cylinders, hoses...everything is original and that's probably most of the problem.

The shake can only be from a few things: warped rotors, unevenly worn pads/shoes, clogged lines causing one side to brake harder than the other, worn tie rod ends, worn ball joints, improperly inflated tires and possibly the steering dampener. Thoroughly checking each should flush out the problem.

 

Take it to a tire shop and get the wheels balanced. That's when it shows up...50-70 MPH.

 

The Garrison steering set up on high boys didn't use a stabilizer.

I agree on the tires, that's where I'd start. you might just swap front to rear if you want to see if it changes anything.

 

Im still running on stock tire size, 235s just replaced the entire brake system. I should also mention that when the master cylinder cap off and pressing the brakes causes the fluid to shoot out almost like it's back pressuring out the lines back to the cylinder. I've rotated the tires about three months ago but never have checked if they are balanced I will get that done today.

 

Well, mine has one and it came stock so....

 

Just to be sure I am assuming the truck is smooth and only shakes when braking between 50-75mph. I always thought with the power assist and the control valve having a closed center spool design which traps oil on either side of the cylinder piston, that actually works to prevent front end wobble, (as long as the steering wheel is not being turned) even better than a standard stabilizer as those work like a shock. On the 5 highboys I've owned I never had a wobble issue of any kind.
I suspect there is looseness somewhere in the steering geometry especially since you don't have oversize tires. Check the rubber mount bushings (rod end) for the hydraulic cylinder. and check the ball joint on the other end of the cylinder for slop. Usually if there is excess wear somewhere in the steering geometry, the truck will wander especially if you let go of the steering wheel. Assume you have checked for excess play in any of the steering components? From the sounds of it your tires must be balanced or you'd know it without bringing braking into the equation. If there was an issue in one of the wheels relative to braking efficiency typically it would cause a pull to one side but you did not mention it doing that so I don't suspect a problem inside the drum.
Keep us posted if you find the problem.

 

I have bought used high boys and my dad bought new ones none ever had a factory stabilizer.. with power steering, manual did have one.

Maybe they were an option but I doubt it.

Either way this wouldn't solve the op's problem.

 

Mine has power steering and come with one. It wasn't an option. I'm not saying the stabilizer would cause the problem, but a properly functioning stabilizer can prevent the problem, or at least compensate for it.

 

How do you know it was original ? I have considerable experience for the last 45 years with these pickups and I have never seen a factory stabilizer on a power steering high boy.

If I'm wrong prove it , there is no concours judging book on 73-79 Ford pickups so this is how we learn . I'm finishing up an extensive expensive restoration on a '76 high boy and if I'm missing something I want it.

 

One painted steering stabalizer won't fix the problem but two polished chrome ones will.

Stabizer on front end that tight do nothing . They also do nothing for bumpsteer or death wobble.

My 76 has a stabalizer im assuming added to be cure all to make it drive better thing wonders all over the rd. All steering joints are shot but supringly somehow has wht look like poly bushings on the track bar. They were on track but apparently decided to give up there.

 

The cure for the crappy high boy steering is the conversion. as you say the stabilizer is a failure of a fix all everyone runs to because they either don't know how to fix it right or don't want to.


As far as the op's problem goes. I suspect it's a combination of problems highlighted by worn parts in a crappy steering system from the get go. you say the drums are true, are you sure of this ? even one out of round drum could set of a rebound effect .

 

I agree. These are old wore out trucks and yes the rebound affect is huge in a sloppy front.
touchy brakes could be spring bosred right into the tie rod ends tht then pogo off themselves

 

I'm not sure if it was an option from what I've seen on older threads there were three main types of steering. Manual, ram assist, and true power steering.
Manual steering (one that everyone says is terrible).
Ram power assist "assisted power steering"( usually on highboys, ton of hoses that leak) I've had to replace 3/4 of the hoses for the thing and everyone is kind of in the middle about this one. Some say it's amazing some say it's terrible as well. Parts are almost non existent for them now and I've looked at the prices for the ram cylinder they are $200-500!
And true power steering(this is the one that everyone wants) good luck trying to find one at the junkyard because everyone with a highboy knows about the hoses on the ram assist steering and are tired of it. I honestly am but because I'm selling the truck I don't plan on doing the conversion.
Don't quote me on this because I'm not 100% sure but I've read many threads about these and this is how I usually sum it up to understand.
One thing I know for sure is true power steering was not an option for highboys. Why? not really sure I think it has something to do with the narrow frame and the fact that 70s was when ford first started playing around with power steering and weren't sure if it would hold up with a highboy.

 

Here's a few pictures of mine.