Shake

[WinslowS]

I just got the truck running today, drove it around the block, and when I got up to around 30-35 I got a horrible shake from the wheel, so bad that it would be impossible to drive any faster or maintain speed and stay in my lane. My dad thinks it is a tire/wheel issue. Its an 89 K5 with 3/4s from an 82 k20 and ~1/3-1/4 tread 38.5 Gumbo mudders, all of which is a recent addition.
Edit-3/17/07 Took it to a shop, aligned front end, balanced and trued the tires. It needed a passengers side tierod end, but that was all. It was working fine until this afternoon when I went wheeling, on my way between mudholes it came back. I described it wrong above the shake is everywhere but the steering, It is like the whole truck is shaking. I took some rear shims out when I swapped in the 3/4 tons, and now there is almost no angle between the driveshaft and pinon yoke. It is not shaking often as it was before. Any ideas?
​

 

[readymix]

Search "death wobble"

 

[73k5blazer]

I was hoping for a thread on Master Shake

 

[WinslowS]

Read update, not a steering issue.

 

[73k5blazer]

For a vibe free driveline you want your shaft with a double carden joint by the tranny and straight into the diff (diff usally needs angled up a bit), OR you want equal angles on each of the shaft.

Any other way is going to introduce vibes in the shaft.

 

[WinslowS]

I'm sort of a noob, whats a double cardon joint? And would these vibes be nonexistant, then so extreme that the car isnt safe to drive. I don't have a tach, so I can't tell if it happens at different rpms, if that would even help?

 

[73k5blazer]

This explains it much better than I can

http://www.4xshaft.com/driveline101.html

And yes, you'll get weird vibes at different speeds. As you accelerate, it may be faint at first, then get strong, then go away then come back at a higher speed.

 

[WinslowS]

I got some shims that were in the back, I took them out with the zero rate when I put the 14 bolt in because I didn't want the front lower than the back, and the shims were increasing angle, while I thought that no angle would be better(I was wrong).
My other thought is that I have a bad shock. I am going to correct these angles, but the shake doesn't seem consistant with the driveline vibes, because once it starts I have to stop before the shake will stop. I'm thinking the unbalanced tires were setting it off before, and I somehow made it worse offroad yesterday, and so now bumps in the road at higher speeds set it off. I went over 45 for a while, then had the shakes at like 30 on another road. I'm also going to try hooking the swaybar back up.
Anyone know how to test shocks?