Sorry, " a lot of wear" means "noticable wear". I can always tell if a trans had ATF or 90 wt gear oil after a lot of miles. Most wear is in the synchro splines, shift plates(shoes), roller bearings and countershaft(inside the coutershaft gear cluster). These are usually replaced, and will bring most 4 speeds to like new performance, barring any abnormal damage. I know Mopar used ATF from the factory. It was the first thing I replaced when I got any four speed or OD trans. I'm talking street performance and longevity. I'll give up a fraction of a second in the quarter mile or a fraction of a mpg. Racing is a whole different use, as OUTLAW described.
