API/GL4 v. API/GL5, SPEEDO Cable

[jad@mail.iex.net (J.A.Dowdell)]

Q-LISTERS,
Can someone explain the differences between API/GL4 and API/GL5. Is the GL5
just somehow "better"? I have some synthetic 80/90w API/GL5, can I use this
in the front trans/diff of my QUATTRO?
Also, since the weather has started getting colder , the speedo is stating
to make some noise and show some movement - only happens when air temp is
low 20's F or colder and then only until the car warms up. Can you lubricate
these things? Maybe also the head unit? BTW, the car is an '86 4KCSQ w/103k
mi. As always, much thanks in advance.
JAD '86 4KCSQ