Well just completed the Trans/Primary fluid change and put in the Spectro 75W140 Gear lube and for the primary heavy duty primary chain chase oil. I have been reading about the GL ratings and looking at the 75w140 is a GL1 and the 6 speed lube is a GL5. What the heck is the difference? I hope I did not put anything in the bike that will do damage to the trans!! What is the difference because reading what is on the spectro site the 75w140 formulated specifically for Harley big twin Trans. I have a 07 Road King with a 6 speed, The Bike does shift better and alot less noise from the trans since doing the change. I did look for the 6 speed stuff but was unable to find it here in Virginia Beach. Just want to make sure I made the right choice or do I need to get the stuff out and put something else in there. Thanks for any help given.