I just did my 10,000 mile maintenance... had mobile1 75w 90 in the tranny.... switched to 75w 140 and it's even better.
Not a temendous difference over the 90, but definitly noticable and smoother.

 

Well curiosity got the best of me, I dumped the Redline 75W90 and tried some Royal Purple 85W/140 and noticed even better results. I am completely satisfied now. It shifts like butter and the gearbox is nice and quiet in 5th especially when I've been on the road for awhile and the gear box is nice and hot. Seems the 140 does well when everything heats up(ie hot day, long run).

I let the guys know up at the Harley shop, the service manager doesnt even run 20w50 in his tranny for the same reason.

 

compared to our dealer here Yours is full of it, have had mine done a three dealer near home and recommends: all three said-- Syn3 in motor::' all three said Formula+ in primary/
2 said formula+ in tranny and 1 said to use Bel-ray 75-140 gear lub,

Syn 3 in the primary and Tranny is not what I would choose and or use...
my tranny clunks and whinnied the worst with SYN3 in there...

this year I am using syn3 motor formula+ primary, and B-R75-140 Hypoid and I really like this set up...there are plenty of others to choose from, just do some homework...

 

dude MOBILE1 is one of the best oils out there,I run mobile 1 V-tween 20w50 engine and primary and 75w90 gear oil in the gearbox,she runs great,I use to run that oil in my warrior for 25k miles never have any problems......