ok this one might take a little to explain.

i put my new drive shafts on. front is a coast and rear is a Trailmaster. now before i put them on i did not have a vibration. now i do. at first i thought it was my tires. New MTR with Kevlar. they are on 15" wheels. so i aired them down to 32 pounds and the vibration got worse. but once i get up to about 35 mph the vibe almost goes away. now i have not had it over 40 mph since i put the shafts on. i'm working with Trailmaster right now on this. could my alignment be a cause for this. it is off alittle. all of my mods listed in my signature are all recent. any help here would be great.

 

if it happened right after the drive shaft install and wasn't there before i think you answered your question.

 

i think the rear shaft might be out of balance. but i dont know about the front. how would i know if the front is off not the rear.

 

remove the frt one and go for a ride. is its still there then its the rear. i would still try with just the front shaft as well

 

How does the front pinion angle look? Is the DS within 5° or so of the pinion? I had a bad vibe in my front DS and just recently got a handle on it. Changed the pinion angle by increasing the lower control arm length and lengthening the uppers.

 

did you install the new tires at the same time

 

they were on before the lift, and drive shafts

 

Did you install the lift and driveshafts at the same time?

 

I will tell you that though many claim to have no vibe at all, I still have the slightest at 40 mph that I have chosen to ignore. I have shafts rebalanced and rebuilt. There just isn't any way to get past the inability to adjust castor independant of pinion angle. I have had my castor at 2 degrees and still had a slight vibe (though it was less), but you wouldn't wan't to drive it that way. I have also had castor at 5, 6 and 7 degrees. I currently have about 4 inches of lift (3 inch teraflex on a 2 door).

Best of luck, and let me know if anything works.