Hello everyone,

I just recently purchased a 1979 Ford F-250 Supercab 4x4. I am working on eliminating a vibration that I get at high speeds. I have read some of the other posts but nobody reposts if they had actualy resolved the problem. I figured I would start a post and update on my outcome. Since I bought the truck in December I have not been able to track down the vibration I get at high speeds. I started off by having my tires balanced. (35" BFG All Terrains) That eliminated most of the hop I was getting but not all of it. Next I took the 2 piece driveline in and had them shorten, balance, and replace the u-joints and carrier bearing. I installed the driveline and took it on the interstate. The lower speed vibrations I was getting were gone but when I get up between 60-70 miles per hour the vibration is there. I tryed adding a couple diffrent spacers on the carrier bearing but it never improved. The next thing I tried was swapping out the rims and tires to a set of 33" Bfg All Terrians that I had on another truck. I hopped on the interstate and it would still vibrate. The one thing I noticed was the vibration started at a lower speed with the smaller tires. Not sure if it was a slower speed or not since the smaller tires probably threw off the speedometer. I also grabbed the four wheel drive shifter at high speeds and I cannot feel any vibration through it. Not sure if that helps but on my old 76 when the u joints were going bad you could feel it in the transfer case shifter. Any help in this situation would be greatly appreciated.

Thanks,
Kevin

 

Can you tell if it's comming from the front or rear ?

 

I believe its coming from the rear.

 

First off, Beautiful truck! Second, Its a little spendy but you might try changing your u-joints.

 

As of last week all the u-joints and carrier bearing are new.

 

Could you remove the rear shaft and try running it on the front axle and see how it acts ?

 

I could try it. I'm not sure if I should run that fast on the front end. I drove that way while my drive shaft was being rebuilt. I only got up to about 50mph.

 

Is the drive shaft "in time" u-joints lined up properly? Checked pinion angle? Nice truck.

 

Driveline is in phase. Im not sure what to look for when checking pinion angles. Any info would help. Thanks

 

So as of tonight I think that I'm narrowing it down. I thought it was the rearend and spent most of the day trying to track down another one. After work I pulled my truck in the shop and stacked up some 6x6 dunage and sat the rear end on it so the tires were in the air. I then had another guy there run the truck at the speed where the vibration was the worst. I soon noticed that it wasn't coming from the rear end. I found the vibration coming from the rear yoke of the transfer case. I am not sure how much movement there should be in the yoke if any. It has a little slap in it but no more than the rear end. I torqued the 1 5/16" nut down as tight as I could get it and the yoke stil had a little bit of slop. If you twist the yoke back and forth there is a slight movement in the yoke where the nut and shaft don't move. Does anyone know if any local automotive shops would keep that yoke in stock?

 

I've never seen a yoke go bad, not saying it can't, but very uncommon. Can you move the yoke side to side ? Some in and out play on the yoke shouldn't be a problem, but side to side means the bearing is tired.

 

Since he said the nut/shaft didn't move with the yoke either yoke is worn out or the output shaft is.
John

 

I've had one come loose before, but was able to torque it back down with no problems. Though if the crush washer on the inside of the axel is smashed from years of milage or over torqued you may not be able to make it work...just an idea. I had a real bad vibration on my 78 when i put some 35" tires on it, but it turned out to be a couple bad bushings in the front end. I also didnt notice it until higher speeds.