I have a lazy boy front tine garden tiller. i want to have the proper amount of 90 wt gear oil in the transmission. I can see one hole with a plug that says gear oil. Do i fill the gear box up to that hole? I looked for a second hole but there is only one.

If the gearbox has oil/fluid and the level is correct, I would dismantle the shifter, clean and lubricate it with dry lube. Using oil based sprays, WD etc, will cause a dust/grime build up and make it jam up again.

open gear box and inspect /adjust linkage

10w-30 for engine oil will be OK.
Synthetic oil is a good choice.
The gearbox for the tines would need to be a heavy wt. lube.
85 or 90 weight.

Small Engine Equipment Parts LAZY BOY Parts Catalog Might try here.

30 weigh oiltdetergent (if available,if not regular 30 weight oil will perform also), as for the gearbox.transaxle for the tines use 80-90 weight gear lube

Hole in the top side casting ... remove the plug. 90 or 110 weight gear oil available at yor auto parts store or other fine retailer who sells lubricants.

you have a plug on the tines housing use a rachet to remove plug and put 90 weight oil in it

It's 90 weight gear oil but most likely the output shaft seal has been gone for a consdierable amount of time and has leaked out and is just now making noise, they don't normally make noise right away after the oil runs out. put oil up to the plug fill hole and watch if it runs out the shaft seal if it does then it will have ti be repaiered.

The gear box can be removed, reset and resealed using gasket magic. It is not a quick fix and during this process I also replaced the tine shaft seals as I had lubricant leaking from the gear-box to the tine shaft. When you are tilling you should avoid rocky areas. It iseems sudden tension due to bouncing is what knocks the chain loose.

DO NOT remove the belt pulley from the top of the gear box. It is unecessary. You must remove the entire assembly from the rear of the machine. It is set in place by 6 bolts and come off as a whole unit. Once it is removed then undo the three bolts and spacers that hold the case in place. Remove the case from the frame by sliding it out the open end. You will have to remove all of the bolts around the outside of the case; a cordless drill really comes in handy here. Lay the case on its side, as you remove the bolts you may experience lubricant dripping from the centers of the removed bolt holes, or at the center holes where the case connected to the frame. This is not a problem as you will need to replace the 90 weight lubricant after you have resealed the case anyway. Once you have removed all of the bolts, using a flathead screwdriver and a mallet or hammer. break the seal around the outside of the case. You may have to go around a few times, but eventually it will pull apart revealing the sprockets, bound chain and remaining lubricant. Since it is open this is an ideal time to check for wear on sprockets and remove any large debris from the case. reset the chain so that the tine shaft moves freely and the corresponding sprockets spin as you move the tine shaft. Using a gasket sealant (Gasket Magic**) put a thick bead of sealant in the center of flat outside edge where the two sides of the case come together. Add a little extra around bolt holes. Replace the two covers snugly together and begin finger-tightening the bolts back into the crank case. Once you have completed this task, go back over the bolts and tighten with a hand wrench. Once the case is back together allow 45m to an hour for the sealant to completly harden before introducing lubricant to the system. Then reattach the case to the rear assembly and then put your tiller back together.

This occurrence seams to be an issue with these machines, however the problem is avoidable as it is persistant use in rocky or hard ground areas which causes causes the system to jump and bind. If you happen upon a hard patch of earth or rocky area, go slow, do not force the tiller and remove any large debris when possible before tilling.

Trans oil! 90 or 140 wt.
I use 140 in my older tiller.
G