My son decided he wants to take the old 39 Chevy truck to Prom, but the transmission growls like a rabid dog. It started leaking too. I have no experience with transmissions. It sounds like some sort of bearing problem. I added some transmission lubricant, but that only lead to a bigger puddle under the truck. How hard is it to rebuild a stock three speed transmission? I assume there are special tools required. I’m thinking if I have to rebuild or replace the transmission I should explore all options. Would a 4 speed give me a higher gear for the highway? If I replace the 3 speed with a 4 speed which one will bolt in without many modifications? Any suggestion would be greatly appreciated.

Thanks, Scott