Len,

I haven't seen synthetic gear lube or ATF (for older trannys) on the approved sheet. However, there no reported failures that I'm aware (however, that doesn't mean there aren't any!) The approved list in MY opinion is marketing with some engineering added. Companies must pay MB to test their product and if passes the tests, then its added to the list.

On the other hand, MB has only approved SAE 90. I do not think they've ever listed any other viscosity, regardless of ambient temperatures. I personally use Valvoline 80w-90 in my differential and don't worry about it.

In my Dodge 3/4 pick-up with a Dana 70, both 80w-90 and 85w-140 are specified depending on ambient temperatures.

In any case, GL-5 gear lube MUST be used. GL-1 thru GL-4 are NOT rated for differentials (but GL-4 is specified for many manual gearboxes).

__________________
Brian Toscano