I have an '03 Silverado 3500 dually. 11.5" AAM rear end. I changed the fluid back in march, and hadn't really thought much about it until recently when looking at other fluids while ordering (I own a repair shop). I stock a bunch of LiquiMoly gear oils, and I've come to realize I've purchased both their 75W-90 GL5, and their 75W-90 GL4+ (GL4/GL5). Should I be concerned that I might have put the GL4+ in my rear end? Will it cause any issues, considering it still covers the GL5 rating? Only anecdote to offer is after towing, I can smell the gear oil, probably out of the vent. No leaks.