My M4700 came from the factory with SUDT in the front axle. I recently drained it and changed to 80/90 gear oil. Now the front left axle seal is leaking gear oil on the floor. I’ll have to open the axle and replace a seal. No big deal….and I DON’T think it was gear oil that caused a leak… The amount of SUDT in that front axle was less than a quart when I drained it. I believe my tractor was just like so many others….UNDERSERVICED…. and the SUDT level was so low it was below the seal (about halfway up the pivot on the left side.)If you are going to drain it completely, your best bet would be the gear oil in the long term because it will cut down on leaks. Additionally, you need to remove the two "vent plugs" (one on the top of each wheel gearbox) and fill each side to that level to ensure no air in the system. Then replace the plugs and recheck the level with the dipstick and add more oil if necessary.
I believe that adding the required amount of gear oil (8 qts) simply brought the level up above that leaking seal and has exposed the fact that seal needs to be replaced. (In fact…. if the axle had been serviced to the proper level …the seal may have been lubricated and not suffered this failure.). IMO
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