The tranny in my 1996 craftsman 15 HP lawn tractor is having problems. It has been whining and growling really loud when going up hills or just driving around regularly. It's also vibrating a lot while doing so. I tried to purge the tranny a few weeks ago and that did nothing. It also seems like its slower than it once was. I don't know If the hydrostatic has ever been serviced but I doubt it. I looked online and people are saying that the oil level is low or worn out which is wearing out the pump. Some also said that when they add oil to their tranny, it makes the whining almost go away. I don't want to end up wrecking the pump. I think the whole unit takes three different types of oil. I never had to take out the tranny or do work to it so what should I do? I could take it to Sears but it would end up costing hundreds or a small engine shop. If not, I could try it myself.