Not sure where to start
 

1994 S10 Blazer 4x4.

Found that transmission fluid was way low when I got the truck. I topped off the fluid and it stunk for a bit but went away. Probably deglazed from running low. Now it revs fairly high but does seem to shift through all gears. It is a bit sluggish and the CEL does pop on and off occasionally. (No I have not been able to run codes).

What I am looking for is possible causes as money is tight. I don't want to R&R for no reason.

Thanks in advance.