I have an old Clark C500Y20 forklift that has a Transmission Oil Leak. It's from 1972 and have been trying to figure out any easy way to fix it. If it sits for 2-3 days, it leak alot but when it's running there's no leaks and the oil level is fine. I'm thinking there is an internal leak, but I don't want to take everything apart. Any ideas how to fix?