1991 f250 351 windsor FI death wobble

[heifner]

My 1991 F250 351 Windsor fi 5 speed 4x4- when I go 40-45 mph my front end starts to shake horribly and it is only getting worse if I go under 40 mph it doesn't shake and if I go over 45 it doesn't shake but now once the shaking starts it won't stop and it is rediculous if it hit the brakes while it's shaking it only makes it worse any idea what could be causing it the ball joints are good I'm puzzled any ideas what it could be?

 

[Fellro]

Tie rods need to be checked, but be certain the tires themselves don't havea broken belt. You don't mention oversize tires, so I am assuming you have stock or about stock sized, but a broken belt will really make a shake and a wobble.

 

[heifner]

My tires are 33s and 12 wide I do believe the ones in the front are worn uneven bad because they came off a truck that was pigeon toed real bad I noticed the bushing/ nipple grease fitting is busted and leaking what looks like oil

 

[O'Rattlecan]

I believe you may have found your problem. They are likely worn and need to be replaced, or at least have a professional look at them and rebalance them if you can.

Ryan

 

[SuperCab]

Or if the rear ones are better, put them up front.

 

[Fellro]

Between the larger diameter and wider size, uneven wear will definitely make itself known.

 

[heifner]

But why would it only do it from 40-45 mph slower or faster drives great

 

[heifner]

And generally happens in 4th gear never in third

 

[Fellro]

Some of it is going to be due to resonance and such, that is why a balance condition only shows up at certain speed. You can mask a wear condition like that with balance. My daily beater is the same way. It has developed a death shake when I brake hard at highway speeds that I am trying to lock down between tire or warped rotors, but I lean towards tire. The thing is, the shake ONLY occurs with hard braking or when real slow. Broken belts don't always mean sever shake all the time. I can find wear spots that indicate bad belts on tires that didn't seem all that bad from driving on them. Best thing to do is swap them to the back and see if there is any change.