ATF Flush vs Drain and Fill

Always drain and fill (and filter where serviceable) with manufacture's bottled/approved fluid every 30-50k depending on vehicle, no problems in hundreds of thousands of miles
 
Originally Posted by eljefino
Drain and fill. The cooler line flush usually involves a lube tech cutting the rubber hose then splicing a barb back in with some hose clamps. Another failure/ leak point.


What kind of hack shop is working like that to do a line off exchange? I have never had to cut a line or splice in, you either remove a hose or line from the radiator, cooler or transmission and use a fitting if need be but not cut into them. On some units that use a thermostat you may need to make up a dummy thermostat block or simply use a fitting on those that use an inline unit.
 
Originally Posted by ABN_CBT_ENGR
Originally Posted by diyjake
What is the verdict nowadays between ATF flush using a machine vs drain and fill.

I was always taught that drain and fill is the only (safe/best) way to change ATF fluid and to avoid using a macing to do a full flush.

To me it seems like true car enthusiasts that like to do their own maintenance strongly discourage using a ATF machine to do a full flush while mechanics / shop owners say using a machine is totally fine and most shops do a full flush with a machine.

Maybe the modern cars are totally fine with using a machine? I do see a benefit using a machine since you get completely fresh fluid but what are the cons?


This is from flushing industrial hydraulic systems but the concepts are virtually identical. Other than the labor involved and possibly clean up.....

There's only one advantage and significant difference between a drain/fill versus a "machine"(power) flush- the machine has a much faster velocity of liquid and can recirculate.

In a system where there is significant contamination, sludge, varnish and even pockets of accumulation- a flush will remove this a lot better than a drain. ( I often have to repeat several times for large systems and even do a cleaning fluid flush then purge)

People have argued that a flush can break loose stuff and make a situation worse but I have proven to many clients that not true at all EXCEPT when someone either short cuts the process or does it wrong. We normally have a blotter cell to determine when there is proper particulate cleanliness and its not fooled any more that a coffee filter is with grounds in it.

However, if your system does not have such conditions then there is no other significant benefit or advantage to a power flush over a drain/fill.


It's not the same. A flush machine only supplies new ATF at the same rate old ATF is pushed out into the flush machine. The pump in the transmission does all the work.
 
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FWIW, Honda calls a drain and fill of the ATF a "flush". That's been their terminology for well over a decade. They are adamantly against using old-fashioned, flushing machines.
 
Originally Posted by Donald


There's only one advantage and significant difference between a drain/fill versus a "machine"(power) flush- the machine has a much faster velocity of liquid and can recirculate.


It's not the same. A flush machine only supplies new ATF at the same rate old ATF is pushed out into the flush machine. The pump in the transmission does all the work.


I know, that's why I put the qualifier and emphasis in my statement.
 
My general sense is that if your transmission has the drain plug and dipstick or other easy way to refill the fluid, then doing periodic drain and refills seems like a slam dunk. I think the idea is to get wear materials out of the tranny frequently and freshen the additives. That's my .2 cents
 
Most cars never get their transmission fluid changed and arrive at the junkyard on their factory fill

this is exactly why most manufacturers now say that the transmission has lifetime fluid in it. Most cars end up destroyed by anything other then the transmission failing due to lack of Lube.

throw my vote into the bucket for frequent and simple drain n fill every 30k-60k miles to always keep the fluid fresh and not let it degrade to the point where new fluid improves shift quality. That was obviously too late of a flush and the transmission was wearing out due to aging fluid. I’d rather flush it out sooner and keep my trans shifting factory smooth for as long as I own it.
 
I do full flush with a exchanger every 50k, I also have a Hayden 679 cooler and a Magnefine inline filter. My transmission shifts effortlessly with no perceptible feel especially when doing lots of city driving where most transmissions get bit jerky.
 
Are we talking about a fluid exchange vs a drain and fill?

I've heard the term transmission "flush" used quite often and I kind of think that's a misleading term.

A fluid exchange should be harmless and the most effective way to replace transmission fluid. They're designed such that the amount taken out and replaced is exactly the same.

The only potential issue is if you started off with the level low or high, you're going to end the same way.

For the DIYer, if your transmission has an easy means to drain, refill and verify level, a simple drain/fill or serious of them is what I do.
Can't change my own or I'll get a condo letter. This is what my shop calls a flush, I think. Should probably get more details next time.
 
Nobody recommends a machine flush, except BG (a snake oil company) and Jiffy Lube and similar quick lubes

One drain-and-fill every interval recommended by the mfr is sufficient
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If you really need to drain more than that, the best way is to just do 3-4x drain and fills, the interval in between which can be anywhere from a short drive around the block to thousands of miles. And even then, this is rarely necessary unless you went like 200k without ever changing the ATF, or if you used the wrong fluid.

Most cars never get their transmission fluid changed and arrive at the junkyard on their factory fill
Yes, the reason they "recommend" a flush is because it a way to make money especially the BG flush. Shops typically charged 120-180 bucks, which means 100-160 buck profit for the shop. When I was a manager at a national chain i was told to sell flushes on every vehicle. Its unecessay a d&f is fine but not as profitable. Also BG incentivizes mechnaics and shops to use their products by placing "coins" of different values in their product which can be redeemed for cash. So the more product you "recommend" the more money a tech can get. Thats kinda shady dont ya think
 
I always drain and fill. I’ve never owned a car where the manufacturer recommended a flush, when I buy a car used I buy 4 gallons of trans fluid ($75 total Valvoline with my last car) and just drain and fill every Saturday for 3 weeks so I am starting from a clean slate and 98% of the fluid is swapped out. On my truck I do it every 15k on our rogue it’s slightly more of a pain so I do it every 30. Outside of maybe contamination I can’t see why doing a flush would have any major benefit aside from maybe saving some time, we don’t flush our engines when we change the oil and I could see a much higher likelihood of contamination in that setting than a transmission.
 
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