How does the fluid in the transmission look regarding color and smell? Old nasty fluid will not be a bright red. Typical to be brown or brownish red. Not to say that new transmission fluid smell GOOD, but it shouldn't smell burnt. The main point here is that when you do the pan drop and filter change, you will still have old dirty fluid in the torque converter. If it isn't practical to have the fluid flushed, you should probably do the pan drop and plan to do it again in the not too distant future.