49- What does the term "Slipping" really mean?
Simply put, it means that as the vehicle attempts to move from a stop, the engine revs and the vehicle barely moves or doesn't move at all. OR, when the transmission shifts from one gear to the next, the engine revs during the shift rather than smoothly shifting to the next gear and the engine rpm dropping accordingly.
It doesn't mean the upshifts are late and the engine revs higher than normal before the shift occurs. This would be a transmission control problem, not a slipping problem.
Put another way, the clutches or bands are not engaging properly and they are not gripping as they should. When this occurs, heat builds up radically and the friction surfaces are burnt along with the transmission fluid. Therefore, burnt fluid (either dark brown or black in color) always accompanies slipping. In the early stages of slipping, a burnt smell will be the first noticeable indication.
Slipping is an indication of a major internal problem that will require a major repair to resolve.
50- What does the appearance of small bubbles on the dipstick mean?
Small bubbles in the fluid on the dipstick is a common occurrence. It is just one of the signs that the transmission fluid needs to be changed, along with color and smell. When the color is turning brown or the fluid smells burnt, have the fluid changed.
None of these indicators necessarily means that the transmission is in bad. They are just indications that it's time for a service.