I'm trying to determine a where a howling noise is coming from in my drive train. The M-20 has had a rebuild kit. I put the car on 4 jackstands. The rear axle was supported by a floor jack to get the driveline angles as close to stock as possible. At 1000 RPM about 30MPH on the speedo, there is a noise that sounds like it is coming from the driveshaft tube midway on the shaft. The car has a new d/s yoke, new axle bearings and axles. I put a dial indicator on the shaft at the midpoint. It's out of true about .030 (30 thousandths). Anyone got any ideas?