Servis Sat 5 cutter/shredder maintenance

My tractor came with a cutter/shredder that is old and rough but mows pretty well. I wanted to do some maintenance on it and haven't been able to find how to check/change the oil in the gearbox or what oil to use. Do I just remove the plug on the back and see if I can feel the oil with my finger?
It's a Servis Sat 5 serial#003426

Oil check plug is surrounded in blue. Changing oil is difficult as there's no drain plug & one must siphon old oil out or turn mower upside down to drain oil out. 85W90 oil should be fine.

Thanks for the info. Is the upper plug where you add oil?

YES

The gearbox on my cutter is the same as yours,

I would lift the front of the cutter up until the deck is flat,
Take the top fill plug out, then remove the lower (check fluid level plug)

If no oil flows out of lower plug opening, then add gear oil as other member said,


If oil flow out then let it drain down to property level,

Too much oil in a gear box can be as harmful as too little oil, if overfull, pressure builds up in the gearbox and can cause an oil seal to burst,

Other issue, if gear box is low of oil or no oil in gearbox due to a faulty oil seal, you can fill gearbox to proper level with John Deere or case IH
corn header grease, this material is more of a heavy thick oil than a grease, it will not run out like gearbox oil, if this works you are golden,
However if the leak is so bad that corn head grease will not stay in gearbox then you have two options,
1. Tear down gearbox and replace seals which rarely works on an old gearbox as the shafts are worn,
2. fill gearbox with regular axle grease, many old gearboxes have run for years with nothing but axle grease,

The newer gearboxs top fill plug have a vented opening to relieve pressure as gears turn but will not allow rainwater to enter

Great info, thanks

Adding to other replies: On the pressure buildup and popping seals, or worn seals, replacing that top ?" pipe plug with a vented plug, like
OEMs are FINALLY installing on new units will save you some leaks. With the plug on the side, not top, I installed a 90 degree ELL to get
the plug vertical then put in the after market vented plug....auto parts stores carry them.

If it gets to leaking on you just suck out the oil and replace it (to the full plug on the side shown) with Lubriplate #109 (in the white plastic
tube) at most AP stores, normally used for engine bearings pre lube in a rebuild. It's thinner than #2 grease and thicker than 140 so it gets
around to do the lubing but stays where oil leaks out.