Differential fluid change 2004 FX4 II
I've got a pretty good leak on the front differential pinion seal, so I'm going to try to fix that this weekend. The manual for the truck specifies SAE 80w90 gear oil for the front diff. I'd like to go with synthetic gear oil, but I can only find synthetic 75w90. Would using 75w90 vs. 80w90 really make a difference?