Horrible shaking? HELP

[blakemartz12]

Yesterday my truck started shaking pretty bad when going through 1st, 2nd, and 3rd gear (it's a NV4500) then after that there was maybe a minimal vibration at highway speed (65). So I checked to make sure the bellhousing wasn't coming loose and got a few of the bolts to tighten up, worst being 1/4 turn. That wasn't it so i replaced both u joints on the rear drive shaft. When I pulled a cap off the rear u joint half the pins fell out. So I figured that was the problem and it wasn't. So I decided to put the truck in 4 wheel drive to see if there was any difference. It felt a little smoother but when I went to turn around the shaking was horrible. The shaking is the worst when shifting into 2nd all the way through 2nd and into 3rd. Above 30 there is no noticeable shaking or vibration. So I'm out of ideas, any thoughts?

[1STGENFARMBOY]

Does it vibrate when you just rev the engine, if not the engine and flywheel is ok, jack up the rear end put it on stands
and go through the gears, see what happens if it don't vibrate maybe its in the front wheel bearings, or
a tire, or in the front drive line some where.

Dar

[blakemartz12]

The truck is fine at idle. So far I've checked the bellhousing to block bolts, replaced u-joints in the rear shaft, tightened up a loose bolt on the tranny mount (which has a small crack in it but I'm not convinced that is the source of the problem, although I will need to replace that soon as well) tightened the bolts on the motor mounts and rotated the tires. I rotated the tires because I have heard with older tires the radial can start to separate inside the tire and cause vibration problems. All of these are good but not the source so I'm still stuck. I think next I will check the wheel bearings. Any input is appreciated.

[1STGENFARMBOY]

The very next thing i would do is block up the rear end and go through the gears, that
will rule out alot of things and tell you where to look.

[oldestof11]

Is it worse when turning?

Check to make sure the lockouts are off.

[blakemartz12]

Ya it seams a little worse especially when turning to the left. The hubs seems to be disengaging fairly easily. Is it possible if the hub is bad that it would feel like it was engaging/disengaging but actually isn't? Thanks

[1STGENFARMBOY]

good luck, some of those things ate a pain to find.

[lectro_static]

Check your tie rods, and the pitman arm.

[blakemartz12]

Well I found the problem today. The truck has a 4"lift all around and the rear suspension blocks are broken. I recently hauled a load of gravel that was probably way too much. The leaf springs appear to be fine but the blocks broke and bent the u-bolts which rotated the top of the rear axle downward causing the drive shaft to be at the wrong angle. So it looks like I need to replace the blocks, replace the u-bolts, and make sure that the rear axle is at the right angle. Should be fun...right?

[PToombs]

Shouldn't be too bad of a job. Just pull everything, get the right blocks, and put in new U-bolts. Make sure you re-torque the u-bolts a few times for the 1st couple weeks.
Good luck!

[blakemartz12]

Ya I'm thinking about going with a 3" block to give it a slight offset between the front and the rear.