How can we check the trans fluid level don't know if there is a dip stick, don't think so.

you can just open the filler plug and just use your finger to feel the gear oil or fill-it up till it pours out. Need un usual size of tool to open it.

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Use a 17mm allen head socket or L shaped key.

If it has been awhile, don't check it. Change it! Remove the fill hole first then drain plug. Dino GL5 oil. Transmission oil is too often ignored. It needs replacement. I do mune annually