Hey Guys,
I have a 1950 Mack A20 model 2 ton flatbed truck. (I know it does belong here, but you guys have a lot of knowledge and could sure use your insight). Somebody installed a 400Chevy SB and 350 auto trans. The front and rear axles and wheels are stock. The PROBLEM: the truck has a growl when your on the throttle after about 20mph. When you let off the throttle it stops. So my thought was the differential was the problem. I tore it apart and brought the 3rd member into the local truck repair to get their opinion. They thought the gears look worn and possibly could be the issue but overall not to bad. Can't find the ring and pinion. So I found a 1969 C60 with a 2 speed rear end that I ended up swapping in. Still the same growl. I just had the trans rebuilt (growl was their before trans replacement), the drive shafts were brought in and balanced. What could this be? Its only under throttle. When you free rev the motor their is no crazy vibration. Any ideas would be greatly appreciated.
