M about 95% sure I need a new transmission and driveshaft, seeing as how my driveshaft is dented, and anytime I go over 50 mph whenever the truck downshifts to decelerate I hear a grinding noise and vibration.

Also, if I hit 75 mph it makes this loud whirringn noise. Has anybody else had these problems, and if so am I jumping the gun?

I had already planned on upgrading the transmission and torque converter so if it has to be sooner than later I'm okay with that.

The transmission and valve body I want from silver fox costs around 1800$ before shipping and core replacement. I get 300 for the transmission core and I think 75 for the valve body. The driveshaft is another 500 bucks.

Any suggestions?