Driveshaft Rumble?

Recently swapped the 8.25 for a D44.Shaft appears to be about 1/2" longer.
The rumble starts at about 65 mph.I am thinking that the D/S angles have changed .
Running the RE SYE and DS on both axles used/using a 6* shim.I am thinking the pinion is pointed too high and needs to be lowered.Have a 4* shim to put in,but wanted your opnion if this was the right direction.
Will measure the angles when I get a dry flat spot.And the shaft did rumble with the 8.25 but at speeds over 70 mph.
Front shaft is removed ,getting ready for re-gear next week.
Thanks,
Wayne

You need to make sure the pinion is in line with the driveshaft, with a zero degree angle, or a degree low if you have some spring wrap. This is where you should look first. If your angles are good, then you need to check out the health of your u-joints.

Nay