tried posting in the garage but got nothing so I will try here. I have a 72 blazer 8" suspension lift 38" PJ's at about 40 mph a pulsating vibration starts and gets worse as i go faster. rides great up to 40 and it starts. high angle drive shaft pinion angle set one degree low to allow for torque. Tire balance is good. I am at a lose from what i have read if i drive it long enough like this I could throw the drive shaft. Help!!!!