Legend Gear 700 trans

When I put a Hurst Syncro/Lock three speed shifter in my '66 (273 with 3 on the tree at the time), I had to build a tunnel to cover it.
With the floor mat rolled back & no insulation there was gear whine that I never heard before. Checking the shop manual I discovered the Mopar approved lube was ATF. I had that replaced with 90 wt. gear oil & the noise went away. It didn't shift worth a damn in cold weather but it was quieter.
Do you have any floor covering?
Are the gears a straighter cut like the GM M-22 which are noisier?
SpeedyEd