200tq transmission, differential and axle lube

[RJA]

Can anyone recommend the best front transmission and rear differential gear
oil to use for a 1990 200tq?  Manual calls for a GL-4 lube for front
transmission (Red Line MT-90 OK?) and a GL-5 lube for rear differential (Red
Line 75W90 Gear Oil OK?).  Any good sources for Red Line products?
Lithium-based grease for center U-joint OK?  How much to add?  Use grease
gun?

Seems my differential has some whine in high gear at low speeds and have
some clunking when with sudden accel/decel, but was told is typical of the
quattros.

-- Rich
   '90 200tq
   '83 Coupe GT