87 Dodge Raider - DL4 vs DL5 Gear Oil

There is a difference between the oils from what I have researched, but found contradictory information if the two can be mixed. I would check with parts stores to see what they can find that is compatible to go into your transmission. All I find is GL-4 All TEMPS 80W,75W-85W

LOL. That's almost exactly what the parts store said. I can't get GL-4 and everyone goes with a GL-5. Which one? What problems? Depends on the vehicle. Neither of us found an official recommendation. He suggested asking transmission mechanics and other Raider owners. Anyone with a Raider want to weigh in?

GL-5 contains sulfur which hardens gears in differentials but destroys the syncromesh bronze gears in transmissions and transfer cases. GL-4 has no sulfur and is safe with bronze gears. I learned this the hard way...