YACT: Changing transmission fluid

[flot]

Ok, yet another car thread. This one is just hypothetical though, and I bring it from another car forum. (which is riddled with misinformation)

Anyway, the gist of the thread was: some guy took his truck to a transmission shop (dead transmission after he had it serviced recently) and they told him this:

If your transmission is old (say over 60K miles) and you have not replaced the fluid every year like you are supposed to. (ie you skipped a few years) then you should probably NOT change it now.

I replied that while this may not be bad anecdotal advice, it was complete nonsense in general. How do you gearheads feel about this statement? I understand that changing the tranny fluid can and will change the system, and that those changes could be for the worse (dislodging debris, etc) but I don't think it's a fair statement, because the guy at the transmission shop is looking at the problem from the wrong end... (since his job is rebuliding shot transmissions)

 

[Scootin159]

I'd say change it NOW, and put a new filter in it. I'd even consider changing it again soon (as no doubt the new fluid will dislodge debris & fill the filter pretty darn quick.)

Only downside I could see to changing it is if dislodging gunk clogs something up....but I'm kinda doubting that. Also dislodging gunk may cause it to leak....but that's no reason not to change it, just a reason to change a gasket or seal.

Even if you have to change it every week for a month to clean it out...it's worth it. Transmission fluid is dirt cheep compared to a new transmission or a rebuild.

 

[JC]

Yeah, should be changed anyway.

Problem is, most torque converters don't have drain plugs....and the converter holds about 80% of that nasty fluid. Changing it several times (as Scootin159 said) may help dilute the old fluid somewhat.

Heck, 60k miles isn't old....most trans service intervals are every 30k, so that's only missing one service


JC

 

[Scootin159]

Originally posted by: JC
Heck, 60k miles isn't old....most trans service intervals are every 30k, so that's only missing one service
JC

Guess it depends on how you look at it. I see that as being 2x over the suggested limit.

Anyways, just to throw a twist in here....my winter beater I'm driving right now I got for $50 because it had a 'blown trasmission'. Turns out that the owners NEVER changed the tranny fluid in 130k miles!. The transmission was so dry, the torque converter couldn't do anything, so the car was essentially stuck in neutral. I just added (and changed out some very black fluid 2000 miles later), and have been good for the last 10k miles.

 

[StageLeft]

I've read that before, but I think most gearheads would probably not agree with it.

 

[Pacfanweb]

All you need to do is have it flushed. That gets all of the old fluid out, whether the converter has a drain plug or not.
And at 60k, it needs to be flushed NOW.

Now if it had 160k and had never been flushed, that's a different story. But 60k isn't a big deal.....some manufacturers don't even recommend the first one until 50k, so 60k isn't that bad.

 

[optoman]

My VW Jetta should be flushed at 100K or so says the manufacturer.

 

[Quixfire]

I'm not a gearhead in real life, but play one on ATOT and I would recommend changing the fluid as long as it's not black with debris in it. Once a transmission gets to the point where the fluid looks like dirty motor oil nothing you do to it, short of replacing it, can save the transmission.

 

[Pliablemoose]

Originally posted by: optoman
My VW Jetta should be flushed at 100K or so says the manufacturer.

If you want to see a puzzled look, go into one of those oil change places & ask them to change your tranny fluid, they'll scratch their head after looking in their database.

The only non-VW tranny fluid that meets specs is a synthetic Amzoil tranny fluid, & no one stocks it.

 

[C'DaleRider]

The mechanic may be right in some terms. While 60K may not be too bad, my brother, a 25-year mechanic with lots of various experience (was a Mercedes, Audi, BMW, Porsche cert'd. dealer mech for years until the dealership sold out to Penske, and is ASE cert'd in almost all the systems on vehicles).......

John says he's seen more than one auto tranny with over 100K essentially grenade after the fluid was flushed for the first time at that mileage. Seems the tranny fluid gradually loses its lubricating properties at that high mileage (obviously) and the tranny wears out/into what the fluid is doing. Putting brand new, really slippery fluid in makes the tranny give up the ghost......bad or no shifting....lose some gears or not get out of park. Says it's a crap shoot......some high mileage vehicles stand up to it, some don't. But his shop won't flush high mileage cars that have never been flushed before, esp. if the fluid is jet black.

 

[tnitsuj]

Originally posted by: C'DaleRider
The mechanic may be right in some terms. While 60K may not be too bad, my brother, a 25-year mechanic with lots of various experience (was a Mercedes, Audi, BMW, Porsche cert'd. dealer mech for years until the dealership sold out to Penske, and is ASE cert'd in almost all the systems on vehicles).......

John says he's seen more than one auto tranny with over 100K essentially grenade after the fluid was flushed for the first time at that mileage. Seems the tranny fluid gradually loses its lubricating properties at that high mileage (obviously) and the tranny wears out/into what the fluid is doing. Putting brand new, really slippery fluid in makes the tranny give up the ghost......bad or no shifting....lose some gears or not get out of park. Says it's a crap shoot......some high mileage vehicles stand up to it, some don't. But his shop won't flush high mileage cars that have never been flushed before, esp. if the fluid is jet black.

I have heard both Pat Goss and the Car Talk guys say that changing tranny fluid after about 100k when it has never been changed before has caused many a transmission to die in thier experience. Take that for what it's worth.

 

[TubStain]

My roomate changed his transmission fluid after about 115,000 miles in his pontiac. He got his car used and didnt know when the last one was done or if ever done. His transmission died promptly and he needed a $1000 rebuild. Seems some metal got stuck somewhere.

 

I agree with that statement that you should not change the tranny fluid if it has not been changed and there are a lot of miles on it (60,000 I do not agree on), let me explain why.

Once a auto tranny has burned it's fluid and has not been changed, the tranny fluid has changed not only it's frictional properties but has also lost all it's additives (anti foaming, anti sludging, viscosity additives) along with the fact that the internals have varnished accumulations, changing the tranny filter and fluid at this point will increase system pressures, clean the varnish off the bands and can possibly destroy the transmission.
I have first hand experience with this phenomenon especially with the weaker Japanese trannies and Chrysler overdrive trannies.

You also have to consider all the band material stuck on the inside of the torque convertor, this will dislodge itself once the new fluid hits it, this by itself will quickly plug up internal passages thus causing a loss of system pressure and eventual tranny destruction.

This is not to say that you should not change the filter and fluid, this must be decided by the tech working on the vehicle because it is different from case to case depending on the amount of burning and contamination, mileage and condition of said tranny.