I have a 4.6 01 F150 with 3.08 rear end I got back in Sept. In Nov. I replaced the timing chain/guides and brakes/rotors all the way around. I have also flushed the cooling sys. and replaced all the coil packs/plugs in Nov. About 2 months ago I started feeling a vibration(feels like the truck is bouncing most of the time not bad but I know something isnt right) at ~37MPH. Not always bad but 98% of the time you can feel it. I feel it at other speeds sometimes also. 2% of the time I dont feel anything. It had older tires and I got a new set ~ 3 weeks ago and its the same. A couple days ago I put a GoPro under it and filmed the driveshaft and it does seem to be bent some. Any ideas what might be my issue or things I can check myself? One other note is the previous owner did use the truck to haul a horse trailer some and I know now that rear end was not the best for that! Truck has 210K on it and engine was replaced at ~ 150K


I went down the street and back and only got up to ~35MPH

 

Check the u-joints with the driveshaft removed. They can seem good in the truck, and bad removed.

 

Believe it or not, these felt good in my Expedition when I first shook them. Then I actually saw the bearing cup was almost gone.

 

Here is a view of the front end towards the engine.

 

U joints look good but I guess I can pull them next and see what they look like off the truck.

 

Ok early morning ? I pulled my driveshaft and Ujoints look good I'll probaly change them anyway but on to the ? I live near a hill I can tow the truck up and coast down to see if there is any vibration with the driveshaft removed. Would I hurt anything? Im thinking not but Ill ask anyway. one other ? the spline shaft coming out the back of the transmission has some side to side play is that normal? Im thinking when the driveshaft extension is in place that holds it steady.
Im wanting to run the engine when I do this so I have power steering and brakes and all.

 

not my video but mine does this. Is it normal?

 

No. It means the output shafts support bushing is toast.

 

There is a bushing in the tail shaft. If your has that much play, you probably need a new tail shaft. My Buddy that owns a trans shop has a tool where you can ream out that area where the bushing is and put an actual bearing in there.

The whole trans won't need to come out, but it's a lot of work getting there.

And you are right, check for play while the yoke is IN the tailshaft. I believe it is 1/16" play you are OK with.

 

What are the odds that that bushing being worn could be causing the vibration i'm feeling? Even if I dont have more that 1/16" play when the driveshaft is installed.