Okay, I am, once again baffled and need some help with a very obvious vibration after I put the rear axle back in.
From the beginning... I had a Dana 35with a 3:54 gear in it. I had it changed to a 4:56 at a local axle shop to better utilize the capabilities of the overdrive, available power and tire size.
Before, no vibration while running on jack stands. After, serious vibration which shakes the the axle at the pinion end up and down about 1/4 to 3/8 inch in an arc, so to speak at a very low speed. (say 10 mph or so on the speedometer)
U joints are (were) good before this. I have removed the drive shaft (again)and double checked the angles at the yokes at the pinion (91 degrees) and at the transmission (89 degrees) the driveshaft is at 5 degrees at ride height. The drive shaft is in phase (both yokes pointed the same direction and checked with an inclinometer on the bench)
While under the truck I can spin the driveshaft by hand and there is no unusual movement, no slack anywhere, no up and down of the pinion yoke. The drive shaft has a slip joint in it, but the length is the same as it was before and it hasn't been a problem prior to this.
No noise from the axle when running. Ran it without the wheels and tires and no noticeable vibration. Checked the U bolts and they are torqued to spec. Put the front tires on the axle (smaller size and lighter and they vibrate less than the rears tires did but more than running with just the brake drums.
Tires? about 20 miles total since new and mounted/ balanced.
The torque at the pinion yoke is in spec and I'm inclined to think that the axle is assembled okay, but short of taking it out again I am going on faith at this point.
The heavier tires seem to magnify what ever is happening but I'm not ready to jump to the conclusion that they are the root cause.
When it's in gear and the tires are turning...driver side turns at constant speed with engine speed. Passenger side moved in a sort of coasting manner and in a rather jerky, start -coast-stop-start type of motion but at a much slower pace (obviously, it's not the driven wheel)
So there you have it...That's as much information as I can muster...
Any ideas?
Thanks:
Paul
