I obtained a john deere lawn tractor 116, used, it grinds when you put it in forward gears, when u left off the clutch. Any ideas?

What type of transmission and oil to use on john deere lawn tractor 116

Planitary gear is bad

Hi,
If it grinds when you put it in gear and acts up while in gear, it is probably the bearings on the input shaft gone bad and the pinion is grinding against the bevel gear. It generally requires replacement of both gears, bearing and possibly some other hardware. There is a serial number break and it is deck dependent, so that info must be available.
Another thing those units do is feel like they are jumping in and out of gear which is damaged shift keys and possibly worn gears.
The transaxle uses Bentonite grease, which may or may not be available anymore. A good quality synthetic grease(I like the Shell and Havoline) will substitute.
Peace,
Clarke