1999 Dodge ram 1500 coversion van
 

Hey Guys Ive been trying some of the techniques you guys use to extend my mpg.
Question is will coasting in nuetral hurt a automatic transmission

No. If you get any symptoms or its behavior is unpleasant then you should stop, but most automatics are fine for coasting with the engine on.

If you plan to shut the engine off then that will probably be a problem. The transmission can overheat or underlubricate because its oil pump is driven by the engine.

I recommend rev-matching while putting it back in D. If you don't, when you put it in D the transmission will cause the engine to speed up. Your job is to speed the engine up ahead of time so that doesn't happen. It saves a little bit of wear on the transmission.

I've been doing it for about 20,000 miles; my GMC full size pickup's transmission now has a total of almost 195,000 miles on it. So far so good.