your tranny should still be spinning with the clutch pushed in. maybe start on a hill with the case in neutral?
is it a 1p/c driveshaft or is there a carrier bearing in the center? I know with mine it could almost get the tires off the ground...dropped the driveshaft, had it balanced, installed it with everything facing correctly, and now I have a minor hum around 40, which I think is tires.
maybe drive around in low range, if it starts at a low speed it's your tranny. if it starts at the same speed, it's your driveshaft.
