What grease in tranny & rear end ?

[Racer57]

70 Cuda with rebuilt 4 speed and 3:91 suregrip rear end. There's a whine that I feel is louder than it should be and most likely from the rear. Not sure if needing more miles for break end or not properly setup. What grease do you recommend ?

[Chryco Psycho]

GL4 75-90 gear oil , synthetic GL5  can be a problem in both , too slippery
 Redline MTL is good too for the trans

[cudabob496]

I had a whine in rear after putting in new 3.91 gears. The mechanic tried two diff brands of gears, and settled on Richmond, but still noisy.
Has quieted down over time. I've use synthetic in rear and tranny for years, but would break in rear with dino oil.