[Cjhstang]

now i know we have more vibration than the next truck being a diesel, but i get alot of vibration through my cab between 30 and 40mph. i get a little vibration over 40 at different spots too, but its mainly between those two speeds. it doesn't seem to matter what gear i'm in...i've checked in 2nd 3rd and OD and they all have the same vibration. i glanced under the truck to make sure all trans mount bolts and engine mount bolts were tight and all looked good.
any ideas? U-joint?

oh and it only happens when there is load on the engine. if i'm coasting at one of those speeds there is no vibration.

 

[RLDSL]

Ujoints are a possibility. with 4x4 you have a bunch extra to consider. Any chance you left hubs locked in or anything else that might add to driveline bind on the pavement? With it only under load it pretty much counts tire balance out.

 

[trampsdieseltruck]

if it happens when you are out of 4x4 check drive shaft u-joints.if it only happens when you are in 4x4 check the front u-joints.

 

[asauer]

Have you done any changes to your driveline lately- i.e. rotating tires, removing the driveshaft and forgeting to put it back in the way it came out, etc?
What kind of 33s do you have on it? If they're aggressive it could be the cause.
How long has it been doing this?

 

[Cjhstang]

its been getting progessively worse. the 33's arent real aggressive. checked the hubs, they're unlocked. not sure if it does do it in 4x4 but it always does it in 2x4. haven't done any drivetrain work in the last year and a half.

 

[73dieselcowboy]

Sounds like u joints to me I repalsced mine about 2 years ago about 3 months later I started to have the same problem your describing checked the u joints and the bolts on the on at the diff had come a little loose tightend them and they have been great eversince but if you have to replace them do them all and the carrier bearing:ford:

 

[ScottFraser2]

All three of the the trucks ive had with the 10.25, the pinion nut was loose on all of them. The yoke would flop around because the splines were worn out on it from being loose. I had to buy a new yoke, spacer, seals and reset my diffs. Have a look just incase.

 

[Cjhstang]

ok thanks for the pointers guys

 

[1dieselman]

If all of the above checks out I would set the rear axle on some jack stands (and block the front wheels) and put the truck in gear and check the drive shaft for any wobble.