After 10 years of listening to my PSC p/s pump "Model TC" whine when it's COLD outside and after trying 3 different types of PSC recommended fluid, I called Redline tech dept this am and got a #'s geek like me and we talked for 30 minutes... 
I've tried GM low temp p/s fluid recommended for very cold climates at $32/pt
I've tried Royal Purple MaxEZ at $7/pt
I tried some other stuff in between...
Redline has great tech support and spent a lot of time looking up viscosity #'s to potentially get rid of my low temp whine...
Here's the scoop on our viscosity at low temps:
Redline Fluid- Engineer discussion
D4 ATF 1200 centistoke at –12F or -25C
34 centistoke at 40C
7.5 centistoke at 100C
D6 ATF 1500 centistoke at –12F or -25C
34 centistoke at 100C
Royal Purple 2000 centistoke at –12F or -25C (currently use)
45 centistoke at 40C
9.06 centistoke at 100C
Tranny numbers comparing Mercon V with Redline D4 ATF
My ‘98 4r70W switch to full synthetic D4 ATF
MerconV 993 centistoke at –24 C
D4 ATF 1000 “ “
Royal Purple 1785 “ “
Redline PS fluid 2250 “ “
MerconV 55. centistoke at 80F or 26C
D4 ATF 57.5 centistoke at 80F or 26C
Mercon/D4 both 7.5 centistoke at 100C
Friction modifiers in ATF for TC , Mercon compatible so don’t worry if you can’t drain all old fluid out if it’s in excellent shape
Friction modifiers are most important for the lockup of the TC . prevents TC clutch shudder w/o it.
Without friction modifiers the TC could shudder and kick into limp home mode
Hope this helps somebody... I'll post up after I go snow wheeling this weekend with a "whine report"...
I've tried GM low temp p/s fluid recommended for very cold climates at $32/pt
I've tried Royal Purple MaxEZ at $7/pt
I tried some other stuff in between...
Redline has great tech support and spent a lot of time looking up viscosity #'s to potentially get rid of my low temp whine...
Here's the scoop on our viscosity at low temps:
Redline Fluid- Engineer discussion
D4 ATF 1200 centistoke at –12F or -25C
34 centistoke at 40C
7.5 centistoke at 100C
D6 ATF 1500 centistoke at –12F or -25C
34 centistoke at 100C
Royal Purple 2000 centistoke at –12F or -25C (currently use)
45 centistoke at 40C
9.06 centistoke at 100C
Tranny numbers comparing Mercon V with Redline D4 ATF
My ‘98 4r70W switch to full synthetic D4 ATF
MerconV 993 centistoke at –24 C
D4 ATF 1000 “ “
Royal Purple 1785 “ “
Redline PS fluid 2250 “ “
MerconV 55. centistoke at 80F or 26C
D4 ATF 57.5 centistoke at 80F or 26C
Mercon/D4 both 7.5 centistoke at 100C
Friction modifiers in ATF for TC , Mercon compatible so don’t worry if you can’t drain all old fluid out if it’s in excellent shape
Friction modifiers are most important for the lockup of the TC . prevents TC clutch shudder w/o it.
Without friction modifiers the TC could shudder and kick into limp home mode
Hope this helps somebody... I'll post up after I go snow wheeling this weekend with a "whine report"...
