Stupid question of the day because the dealer is closed and my manual is at the shop.... Does the front axle use the same hy-gard low viscosity fluid as the rest of the tractor?
The manual for my JD 790 states to use John Deere GL-5, SAE 80W90 in the MFWD front axle. Don't know if your 4210 would be the same, but I doubt it would use a different type of fluid??? Maybe another can check their manual and say for sure.