Urban legend or truth - ATF
 

I have an old automatic accord w/ 207k on the clock and have changed the ATF once, maybe around 20k.

It's still functioning fine, other than a squeal in reverse sometimes.

I've read on a couple forums that mention not changing the ATF on old trannies if they have not been regularly serviced. Has anyone had any first hand experience with this?

I changed the ATF in our protege @ 180k km because it looked a bit dirty, it had never been changed. Initially (week or so) it shifted harder and held gears longer.

That said the fluid now has 40k km on it and looks like new, car runs very well on it's daily 150km commute. YMMV

There is a correlation between flushing high-mileage autos, and failures shortly thereafter (within 10k). Now, would those same transmissions have failed on their own? Correlation doesn't mean causation, however, I refuse to flush any trans over 125k. I've refused transmissions after the test drive, which had less than 75,000.


I don't see the cost/benefit analysis of the $100 for a flush being worth it. However, I live in PA, where rust would already be eating the car alive. If it has a clean chassis, I wouldn't hesitate putting a tranny in it, so $100 for a flush doesn't seem to bad.

I've seen multiple transmissions fail within 100 miles of flushing.

My approach to this with high mileage cars is just to gravity drain whatever will come out, then top off the fluid to proper levels. Then repeat during the next oil change, and call it good. I like this because I get some new fluid in there, but don't run the same risks as a flush.

I have heard this before as well.

Flush the transmission fluid and it'll die.

mine failed about a week after a change when it started showing signs of slipping/missing shifts. i believe it was the reason for the ultimate failure.

OP: I'd just wait until the tranny dies, then do a drain and fill on the new-to-you junkyard tranny.

I think this^ is the key; a power flush / fill can be screwed up, apparently very easily.

What I didn't mention is that I need to change the axles, meaning I need to drain my tranny. :vash:

Should I save and reuse my old fluid?

IMO, it's the actual flush itself that can cause damage. Use fresh fluid, and don't think twice. You're not going to get much at all out, compared to the total volume in the trans, TC, and cooler. Also; Drain and fill is not flushing. I have no real issues with drain and fills, and if flushing with straight ATF, I'm still not that worried. It's mainly to "conditioners" and "sealers" that often get added that keep me up at night.



It's been a while since I pulled a honda axle, but I normally just put a drain pan under the axle port on the trans, pry it out, and shove the new one in. Top off if necessary.

wayy too many auto trannys do not have a drain plug, and wayy to many shops "flush" the tranny by vacuuming out the old fluid through the dipstick tube, then refilling with new fluid the same way. In order to refill such a transmission correctly, you must remove the pan from the bottom of the transmission, replace the filter inside of the transmission with a new OEM filter, then replace the pan and fill. Some transmissions may require turning the drive shaft and/or cranking the engine. After you fill the transmission, idle the engine for a few minutes then check fluid level again, add fluid if necessary. Then drive the car around the block and check fluid level again, add fluid if necessary. Then drive to work and check fluid level again, add fluid if necessary.

Scott is correct, correlation doesn't mean causation: consider the driver who decides to flush his transmission; why did he suddenly decided he needed to flush his transmission? Was it because his transmission was "showing signs of needing a fluid change"?

That's like saying "You'll live longer if you drink a glass of red wine every day". Complete garbage. The study correllates "drinking a glass of red wine every day" with "living longer", but it does not consider the complete lifestyles of people who can afford and choose to drink a glass of red wine every day.

In my limited experience, the most important part of the transmission "flush" is replacing the internal filter. No shops which upsells a "transmission flush" to their customers on top of an oil change for $59.99 is going to pull the transmission pan, change out the filter, re-seal and close the pan, wait an hour for the liquid gasket to dry, THEN refill the transmission.

Those shops are not also going to idle it, check the level, drive it through all gears, check the level again, and then hand you the keys.

The jiffy lube will tell you that the reason they empty the transmission through the dipstick tube is because the "stupid manufacturers don't add drain plugs to their transmissions anymore". What the dipshits at Jiffy Lube don't know is that the reason the "stupid manufacturers don't add drain plugs to their transmissions anymore" is because the manufacturer knows that if you drain and fill the transmission without changing the filter, you're going to kill the transmission. They don't add an external filter primarily for cost reasons. External filter means higher mfg cost means higher price tag means that the consumer is going to buy a different car. The manufacturer is also willing to bet that you won't need to change the fluid during the warrantee period anyways. Why add an external filter, pump, lines, accessories when the fluid might need changed....once?....during the lifetime of the car.

In my prelude, it started acting weird and we paid something like $150 to flush it. for reals, for reals (took over an hour, had it on a machine, and ran it through gears and crap).

maybe two years later the same thing started happened; it got really clunking into gears.

So I did a simple drain (honda trans had drain plug and fill port).

and like two days later the car could barely shift, failed to go into gear, and stranded my wife in the middle of DC in rush hour traffic. I'm a firm believer that if you don't do regular auto trans fluids, then leave it the fuck alone. I've heard plenty of similar stories; even teh guy who bought the car from me a few days later was like "you shouldn't have touched it"

My auto trans in my daily failed @ 80k and never had a change. I bought a used 40k trans and put fresh ATF in it at that time.

Seems to shift, and feel much better than the old one.

I think it can go either way. Auto's suck, i've never had good luck with them.

Mine was slipping on my F150, so I took it to a shop to have it looked at. They basically told me its on its way out, I had them put a new filter and fluid in it anyway (didn't have the money for a new transmission). Over a year later I still get an occasional slip, but it hasn't blown up yet.

I've always seen cars that get power flushed by the machine fail. The flush is too forceful or something. If you want to flush a tranny normally what you do is get 2 5 gallon buckets, and a couple gallons of fluid. Get the drive wheels off the ground. Disconnect the outlet of the trans cooler and stick that in one bucket, put a random hose on the outlet of the trans cooler and put that in the other bucket, then pour a gallon of the trans fluid into the first bucket and start the car. Someone needs to monitor the fluid level in the bucket and keep adding it and someone needs to go through all the gears at low rpm. And you keep going until new looking fluid comes into the waste bucket.

Bonus points for replacing the filter and refilling after.

Lots of good points.

I haven't seen a vacuum machine for the dip-stick, although it seems like an easy sell to shops; as anyone could use it. The big thing for me is checking on all-data or whatever, to see HOW to check the level. Some cars want the trans in park, running, some want them off.

My tranny flushes always just tap into tranny cooler lines, and feed in fresh fluid, while taking the nasty stuff that would normally go to the cooler. I like to use a lot of fluid too, like, up to 20 quarts. Basically, twice the total capacity of the trans alone, or when the fluid going into my waste tank is clean. Shift it a few times, check the color again, maybe add a tenth of a quart through the dip stick.



This is why I always test-drive. Any customer that comes in and mentions "my trans is acting weird", gets the number for the tranny shop. I don't play games with transmissions.


I'm not much for changing filters, as the trans pan often leaks afterwards. :dealwithit:


Long and short: I hate autos. PITA mainly. How much is a Power Steering flush on an R-Package? :giggle:

Interesting read guys. I had not even heard of this.

+1, i never would have imagined an auto trans failing because of putting new/fresh fluid in it. TIL.

Another reason why autos blow chunks and I will never own one.

My brake inner pad fell out tonight. lol. Brake went to the floor and after a few pumps it pressurized. Where was the brake screech warning? It went from braking fine to metal grating. Still my own fault...dumbass.

I was suppose to change this moronic Honda captive rotor bullshit over the weekend, but my thesis took precedence since my mentor has been pushing for it to be done.

School vs my life. Damn it would suck if I died after all this schooling. At least I wouldn't have to pay back $500k in loans.