What type of oil in the gearbox of a 1976 suzuki a100.

https://www.autodoc.co.uk/car-parts/gearbox-oil-and-transmission-oil-11915/suzuki/swift/year-2007

the top should be electric motor with a left and right cable and gearbox

The gearbox takes motorcycle gearbox oil 20w40, this can be the same as 4 stroke motorcycle oil, the capacity will be marked on the casing next to the filler 1.5l or similar. Dont use car oil or the clutch may slip.
The oil injection is separate and different , use 2 stroke engine oil. buy from a bike shop or some auto shops.
I had the 1977 model from new, one of the best trail bikes I have owned.

Shared oil for gearbox and motor.

Be carefull not to put automotive oils in her. Generally bikes have a wet clutch and any newer synthetic oils designed for clinging on for quick starts will ruin your clutch. There are some great oils for big single thumpers at good prices. The site below has exploded view diagrams for your bike along with all the part names.

Goodluck and cheers.

http://www.cmsnl.com/yamaha-xt500c-dual-purpose-1976_model8577/partslist/

Remove the oil guage and pour oil through the openining. You may need a small funnel to do this. Good luck.

The VL1500 has a integral gearbox, it uses the same oil supply as the engine. Once you drain the engine oil you will be changing the gearbox oil. Suzuki's are not like Harley's with a seperate gearbox, also it will pay to use a good quality oil filter.

your gearbox runing with indentical engine oil ,gearbox and engine its indentical cranckcase

Change the oil in the gearbox.Hidraulik oil is the best.

Stop riding the bike until you change the gearbox oil and oil filter. Yes, the oil is probably the problem. I am somewhat surprised that the pistons haven't seized yet. On the bottom or lower side of the gear box there will be an oil drain plug. Drain the oil and put in new oil. The oil fill hole is probably on the right side cover near the rear of the casing. The plug will probably have a dip stick to measure the oil level. Put in 10w40 motor oil. Ride the bike for a few hours then drain the oil to help flush out the dirt and grit built up in the gearbox. Put in fresh oil and a new oil filter if the bike has a filter.

Your bike is 18 years old and parts can be difficult to find. Your bike probably has an oil filter. If so, it desperately needs a new one. Google " vintage suzuki motorcycle parts " . I can not find a free service manual online. You may be able to buy one at www.repairmanuals.com

It would depend on what Transmission u have, Auto or Man
I presume you mean manual when u say gear oil not trans fluid ,

But just in case you can Have a look in the suzuki owners forum for an exact volume of gearbox oil capacity
Visit the Suzuki Car Forums


Try draining it into container to get some idea