Vibration starts to become noticeable around 20mph until it's really really bad around at 30ish mph, and then at 35mph it just stops, doesn't phase out, stops.

-Above 35mph no vibrations, just did a 800 mile trip towing a car trailer with no issues other than when having to slow down and cross the "vibration speed".
-Happens while on accel and deaccel
-All 3 ujoints done about 3000 miles ago, greased all the time
-Clutch in, neutral, in gear, doesn't matter still shakes the **** out of the truck
-Vibrates the WHOLE truck, and seems to be getting worse...
-Diff has been leaking since this started and seems to be getting worse...
-Tires recently re-balanced...

Any pointers guys?

 

u-joints all tight? lift it off the ground spin d-shaft by hand in neutral wiggling for slop

 

If you're hub are locked in, unlock them and start there.

 

Have you checked all of your leaf spring packs and steering to make sure everything is tight?

 

The speed is slow, but this describes a wheel balance problem, did you throw a weight? ...Mark

 

Driveshaft is as tight as the day i did the ujoints.

Hubs are unlocked.

Can't really feel the vib through the steering wheel so I was suspecting it isn't anything in the front end.

Leaf packs are toight, fresh ubolts a couple thousand km ago from when i got the front end lifted and the truck aligned.

Pinion seal is leaking, and tires were balanced with a bubble balancer, which seemed to work great when they mounted the tires last year.

I'll get under the truck this weekend and get it up in the air, maybe i've missed something. I'm also going to try to get someone to drive beside the truck and see if they can see anything odd while it's vibrating.

I don't mind when something breaks on the truck, as long as i know what it is. This is driving me nuts.

 

I'd give the tires a spin balance

 

Just seems weird at such low speeds to be tire balance...

 

Are the rims on straight?

I left the tire shop one time and as I looked out my mirror I saw my rear tire wobbling back and forth, the tire beater installed the outer rim on top of the dowel, I know you don't have duals but your rim might not be torqued on straight, heaven forbid your rim is loose and centrifugal force is straightening it out.

Jim

 

Not probable, but your drive shaft could be unballanced, front or rear. (not sure if you have a 2 or 4wd) You can use big hose clamps on the driveshaft to troubleshoot.

If you decide to try this, I have the procedure. PM me, I'll send it to you if you need it.

Another posibility, also not probable, your rear end might not be tracking straight.

I'd be more inclined to go with Jim.

 

Pinion angle? Transfer case output and pinion angle should be parallel with each other plus a couple degrees to account for axle wrap. If the pinion seal is leaking and wasn't before the problem, I would start looking why... Check the vent tube on the axle as well.

 

D'oh, retaining clip on my middle unjoint didn't seat and must have fallen out, and so the cap backed out causing it to be out of balance...

New clip and no vibration!

 

Well that could have been worse. lol