My truck is a 93 supercab 2wd that I have lowered 3/4 with a chassis tech kit, at this time I put a 4 degree shim to adjust the pinion angle and the truck drove fine.

I then removed the overload spring from the bottom of the leaf pack for another .5 - .75" drop and put on a sightly shorter tire this resulted in a shudder/vibration when starting out from a dead stop.

So I added a 2 degree shim, for 6 degrees total, and this fixed the shudder/vibration from a dead stop.

Now I am experiencing a shake when I get above 60-70 kilometers per hour, it shakes the passenger seat when cruising on the highway.

It feels like it is coming from the rear of the vehicle, no shake in the steering. It is like I have a tire that is low or out of balance but the pressures are fine and the tires were just mounted/balance a couple weeks ago. I thought about it possibly being a rear brake dragging but when I get to where I am going the drums aren't hot to touch and my mileage doesn't appear to be affected.

I think I may have some pinion angle issues but am not sure, can you please take a look at this picture and tell me what you think of my pinion angle, this was taken with the truck on level ground.

 

Yes, sounds like driveline issues. The working angle at the rear u joint needs to be very close to the angle at the front/trans u joint. Use an angle finder on the trans and adj the axle to the same and go from there. One piece shaft? If it has a center bearing,it gets a little more complicated. An online search will bring up lots of info on setting up custom driveshaft angles.

 

Looks like the pinion is up just a tad...

 

It's way off (by degrees).............good discussion/ideas (e.g. double Cs/CVs) here..........

Driveline 101

 

I had it put up on a hoist so I could get a better look underneath the angle of the rear pinion in relation to the tranny looks really good. I checked all the u-joints and they are fine, I pulled the rear tires off and checked for bulges, there were none, I checked the rear brakes to see if they were dragging, they weren't. It also didn't appear that the drive shaft or wheels threw any weights.

About the only thing I noticed was that there was a lot of play in the rubber surrounding the carrier bearing so I pulled the drive shaft out to get a better look. The rubber has deteriorated a bit and there are some tears so for the sake of $30 I bought a new one. I will be putting it on tomorrow and will post the results after it is installed. Hopefully this is the problem, fingers crossed.

 

3 joint shaft? Can't have angle on all 3 joints. Opposite angles on 2 and straight on the other. Prob need to raise the carrier bearing.