Trany flush vs. drain


This question has come up before,but i haven’t got a good reason why my vehicles tranny’s should be drained instead of flushed. My GMC manual,and Honda manual,dealer,and trusted service station say to flush. Why do some people say DON"T flush?


The idea is to clean or replace the filter and to remove the debris sitting at the bottom of the pan. A flush won’t do this.

Some recent automatic transmissions do not have filters, so I hear, and cannot be serviced in the traditional fashion. As always, abide by the instructions in the owner’s manual.


My confusion is on a practical side. If you flush only, then the filter is left with more gunk inside. If you do a pan drop, change filter and flush, then the new filter is full of old gunk. If you flush first, then do a pan drop and filter change, the mechanics around here will charge you for two services. I decided getting a new filter and doing a pan drop is more important than the flush. On most of my vehicles (Subaru being the exception), I get the filter changed every other time (30K interval), and let them do a flush in between, a kind of a middle of the road approach. So far no negative consequences from my choices.


I just checked my owner’s manuals for the Honda and GMC. GMC say flush,and Honda drain and fill.
I’ll guess i’ll go by the manuals.


Because, after the flush, the transmission doesn’t work right or doesn’t work at all. It happens a lot more than you would expect. Fear is a motivator. How much motivation do you need? You will have plenty of it if it happens to you. You can be forgiven if you find disasters to be amusing as long as you learn from them. Keep your own from happening or just play the odds and flush it away.


PDV, you should write a book full of pithy sayings such as the above “You can be forgiven if you find disasters to be amusing as long as you learn from them” and “Fear is a motivator. How much motivation do you need? You will have plenty of it if it happens to you.”


flush with filter change,flush cleans the convertor,and cooler,does zip for filter.
drain and fill leaves cnvertor full of crud,hoses full of crud,cooler full of crud


For me, an acceptable flush involves NO chemicals. A connection at the automatic transmission inlet hose to new A/T fluid, and a catch for the old fluid from the out line (until the new A/T fluid started coming through) does it just fine. I can then drop the A/T pan and change the filter (if changeable). So what if I lose a couple quarts of new A/T fluid?


If you change the fluid in accordance with the maintenance schedule, there won’t be any crud to flush out.


correct but who does as requested,and warned,very few,all an A/T is a huge fluid pump,that does wear clutch packs and creates a pile of heat and crud i dont care what you do,you WILL ALWAYS HAVE WEAR,some more than others due to the fact some have kids that also drive the car and do more damage in two days…then most adults-34 and over will not create in 2 yers


I would write them all down, but I have so many of them it would take another 53 years to get em on paper. I wasted a few here because the original poster is going to go by the manual! Just the answer I like to hear. Military: It sounds like the Lieutenant and the Chief would fall on their faces repeatedly if they didn’t have me to hold them down the first time. I get no credit for what I do.




DUH! never use chemicals,other than OEM rec ,there are machines we use for that purpose…step into the now