My one ton has a vibration which is becoming unignorable. Its a 93 with 210K on the clock. Since I got er I noticed a vibration whenever accelerating hard especially more when pulling a load.

I had the passenger side u joint replaced on the front shaft in november because it had rusted down to the thickness of a q-tip and I thought I might need 4wd here in Maine. I'm not sure if the vibration started getting worse then.

The vibration seems to occur slightly whenever hard acceleration is happening. In third gear, the truck and feels real bad. Going gingerly up a short hill in third, the steering wheel will nearly bounce up and down in my hands. Back off the fuel and the vibration goes away. I can replicate on the flats, just open er up and she starts squeaking (from the rear end area) and shimmy'n away.

Thoughts on what might need attention?

 

hey there fellow Maina

bouncing like this,i usually start by inspecting the wheels.
with these bad roads and all the road salt mess,it could be you have chunks of salt/sand mix hanging onto to your rims throwing your balance off.
have you been driving the truck last few rain storms? that would have helped.
since we're hopefully done with the salt mess roads this year i took mine into the self car wash and blew off all this mess for the year.

take a look around both sides of the rims to see if you notice any weights missing.
is it a dually by any chance? these can really hold a lot of road salt/sand mix.

then of course inspect your U-joints for any play.

 

The wheels are totally clean. I spent a shiny 5$ bill at the carwash, just today It is a dually.
I should re-emphasize.... there's always a vibration whenever the vehicle is in gear - it gets worse when accelerating - and it's way worse in 3rd gear.

How much play it too much?
Could the drivers side front u joint cause that kinda vibration in the steeing wheel when I'm running in 2wd?
I was thinking probably main drive shaft or even motor mounts... ?

 

If your hubs are unlocked the front driveshaft isnt even turning. You should be able to spin the axles at the outer axle joints if they are unlocking like they should.

 

Ok, I just checked and the hubs are definitely unlocked and the front axles are and were freely rotating.

It just seems weird to me that I can get on the fuel hard in 1st and it's fine, 2nd starts to shimmy when you open it all the way up, 3rd it feels like I'm driving on a rumble strip unless I drive like grandpa, 4th is back to a little shimmy, and 5th even less shimmy.


Differential cover was replaced last summer, with fresh 90 weight and proper ratio of ford anti slip added. I haven't checked the level but I imagine still pretty good. I've only driven a few hundred miles since then. I guess that's one place to look, but what else should I be looking at?

 

Check the yoke on the pinion shaft. It my be loose or just wore and out of spec. Make sure the little ears arent corroded badly

 

Gotcha, anyone know the specs? Should I be checking for forward backward (in relation to the vehicle) freeplay or side to side? It certainly could be that, this truck loves to bath in salt water. Rusty is an understatement.

 

It's side to side. If the tabs wear the shaft isn't centered with the pinion so the driveshaft turns with a slight wobble. They are easy to change but im not sure on the cost or specs.