I agree with Bob. It's gear oil and you never change it unless you had excessive debris in there. "Can't find it grind it".

I have a very old suction device made for removing and adding oil into transmissions, rear dif etc.

I will post a pic. You can get a bottle of gear oil with a hose attachment. That will work.

To remove old oil:
- open/remove upper oil plug on transmission
- note the level of oil, put your finger in the upper hole
- open/remove lower oil plug on transmission, have bucket under plug to catch oil
- when all oil removed, put bottom plug back in
To add new oil:
- put hose on top of bottle
- place hose in top plug hole, tilt bottle bottom end up, squeeze oil into tranny
- your full when the oil starts to come back out. let it drain so the most you have is oil to the fill hole (top plug)