I would use those terms interchangeably…but I’m sloppy that way. the only difference I could conjure up would be the use of some special “flushing“ fluid to clean the old grime out before refilling with new fluid, instead of merely “exchanging“ the old fluid with the new. Given that “BG” is mentioned, I suppose the cleaning/flushing substance is a possibility, so I better get better with my terminology. In the case of my Ford 6r80 or whatever my 6-speed truck tranny is called, I had the fluid EXCHANGED…supposedly… at the dealer. I expected they had to get it good and hot, to get a check valve to open, but I don’t think any special chemicals were used.
I don't know how the BG system works today or how they define a "flush," but they used to add a solvent to the old ATF, and then using their fluid exchange machine (which they sold or rented), circulate the solvent and old ATF, drained the contaminated mix, and then added new ATF.
A pressurized or 'forced' exchange is what caused problems.
The AT shop I work with prefers to do a fluid exchange using the transmission's own oil pump when the customer specifically asks for a complete fluid exchange all at once; otherwise they do a drain-and-fill. In both cases, if the transmission has a filter, they replace it.
When purchasing a used vehicle (as all of mine are), my
Modus Operandi is to do a series of drain-and-fills until the fluid remains clear for at least 5,000 miles.
In the case of my 2012 Frontier, I had to do 5 drain-and-fills before it stabilized. The original fluid had the consistency and viscosity of a 30 grade engine oil that had been run past it's prime. I don't think the ATF had ever been replaced. The AT only had 32,000 miles on it when purchased.
