anyone flushed their tranny?

[Jeg Norge]

so bmw says tranny fluid is life time. i dunno, how would u feel if bmw starts to say engine oil is life time? or brake fluid?

to flush or not to flush? also i heard that some people say the dealer actually doesn't flush all the fluid. just 50% or something like that. hmmm... a flush job is $500 so i wonder if i should do it or not. my 09 30i has 60,000kms.

[Quicksilver]

Try the search button. Tons of responses for this subject.

[soldmystang]

planning to do mine. 70K miles so i need to get at it. seems you can't really get all of the fluid out. the sheet is like $60 a quart and it takes something like a bazillion quarts to fill.

way too expensive but cheaper than a new transmission.

[ard]

I am a huge proponent of changing your ATF. A 100% fluid exchange.

I would be cautious of any old "flush'.... the only flush I'd consider is one that uses the pumps in the tranny (ie natural flow) to pull in fresh and drain the old.


Or do 3 or 4 repetiive partial drains and fills, to get to the 95+% range.

Lots of posts in E53 I am guessing

A

[JCL]

Originally Posted by Jeg Norge

So BMW says transmission fluid is life time. I dunno, how would you feel if BMW starts to say engine oil is life time? Or brake fluid?

To flush or not to flush? Also I heard that some people say the dealer actually doesn't flush all the fluid, just 50% or something like that. hmmm... a flush job is $500 so I wonder if I should do it or not. my 09 30i has 60,000kms.

Transmission fluid is not engine oil or brake fluid. The applications are completely different. Engine oil gets contaminated by byproducts of combustion. There is no combustion in your transmission; if there is, you have bigger problems. Brake fluid is hygroscopic, it attracts water. It doesn't stop being non-compressible, it just gets water in it. No water in your transmission.

Not sure if you really mean flush (ie with a flushing machine) or just drain and fill. Completely different. I wouldn't use a flushing machine. If you drain it, 50% stays in the torque converter. Agree with Ard that 3 or 4 changes will get most of the old fluid out. Gets expensive, though.

There is nothing wrong with clean fluid. However, you are assuming that the fluid in your transmission will contribute to a potential failure. Your transmission could fail for many reasons (sensors, wiring, actuators, seals) that have nothing to do with the fluid.

Lots of seemingly endless debates on here about the pros and cons. I wouldn't do it, personally.

[ard]

I'll add to JCLs comments.

Other than "combustion byproducts" there are multiple other factors that break down oil or ATF: mechanical stress shears the molecules, and heat directly leads to breakdown.

The argument..er discussion...typically them turns to "so you say don't do it?"...."ever?"... "so, 200,000 miles? Never?"... "oh, Ok then sometime before then?"...

But then the response is "why bother changing the fluid, the ATF will fail for some other reason anyway"

(Did I capture that discussion right? )

A

PS Even worse is the whole "Don't need to do it, BMW doesn't recommend it" argument you get from BMW dealerships at 50, 80k miles...then at 105k they say "well, there's a lot of miles on that thing, we'd be concerned that a change at this late stage could stir up issues"...catch 22

[JCL]

Yes, that's pretty close, I'd say.

Agree that shear lowers the viscosity of the oil over time, but friction materials increase it. And the transmission is designed to adapt to changing viscosity. My main point with the combustion byproducts is that this isn't an engine application, that is a flawed analogy. It is primarily a hydraulic fluid application, with a low grade lubrication requirement.

[Jeg Norge]

btw what makes ATF fluid so much more expensive? does it have gold molecules inside? lol

[Lubehead]

Actually, I don't think there's anything low grade about modern automatic transmission fluids. In fact they are amongst the most complex fluids available. Automatic transmission fluids typically contain antioxidants, antifoam agents, viscosity modifiers, antiwear additives, friction modifiers, and seal swell modifiers.

Formulations vary from manufacturer to manufacturer with sometimes subtle differences in friction modifier chemistry. The oxidation resistance of these fluids is especially high, allowing the long service life now generally reccommended by most OEM's.

In addition to acting as a hydraulic fluid, these products also lubricate gears and bearings, and must be able to withstand severely low start up temperatures as well as extremely high bulk oil temperatures particularly in severe service like towing.

The high temperatures ultimately take a toll on the fluids life as byproducts of oxidation accumulate in the form of depleted antioxidant inhibitors and contaminants from the clutch plates, as well as oxidized base oil.

Changing the fluid in a timely fashion cannot help but provide extended component life. Keeping the fluid relatively clean and fresh enables it to effectively deal with preventing the inevitable results that would occur if it was not changed. Reduced wear, reduced deposit formation and superior performance in both cold and hot temperatures is ensured by a proactive approach to fluid maintenance.

[ard]

Originally Posted by Lubehead

Changing the fluid in a timely fashion cannot help but provide extended component life. Keeping the fluid relatively clean and fresh enables it to effectively deal with preventing the inevitable results that would occur if it was not changed. Reduced wear, reduced deposit formation and superior performance in both cold and hot temperatures is ensured by a proactive approach to fluid maintenance.

So what, every 100,000 miles as the engineers at BMW have carefully determined?