Transmission Fluid.... Is it true???

I have always heard that if you havent changed your transmission fluid in say over 90k-100k miles that it would do more damage to change it at that point then to leave it alone. It is sayed that new fluid will damage the old seals. I cant see this being true...so i ask, Is it true?????

Its not true.....to a point. whats happened in the past is people would wait till the trans fluid was brown and burnt smelling and then did a change or flush and the damage to the trans was already done, then they wanted to blame the problem on a trans fluid change, not poor maintenance which was the real culprit.

a trans flush is never a good idea though.
a flush most likely will hurt your trans

ya know, with people coming behind you and posting nonsense like that, the hell with it, I have better places and better ways to spend my time.

ya know, with people coming behind you and posting nonsense like that, the hell with it, I have better places and better ways to spend my time.

Calm down man, he has a point to some degree. Transmission fluid change and trans fluid flush are two slightly differnet things. A fluid change is where you allow the trans fluid to drip out on its own and disconnect the lines to get it all out, then you put new fluid in and you're good. That NEVER is harmful to your transmission. The problem is when you do a flush on a really old transmission. Flushing is when you hook up the trans to machine that forces fluid into the trans while draining the old one out. In the process, you're dislodging sludge in the tranmission that could clog lines or valves. That could be harmful to your tranmission.

So let me get this straight, I work at the infamous Jiffy Lube and we offer a T-Tech service which basically is just a machine that will continuously allow new fluid in while capturing the old stuff, the cycle is powered solely by the trans in Park. I was talking to a mechanic (buying some parts) and he said that is the best thing you can do to a trans since it doesn't expose it to air and it's a full fluid exchange, better than a drain and fill.

so a t-tech is not a flush and is OK with all trannies? My "boss" (a :screwy: :licka: :popcorn: ) has declined doing the service ($99, high profit) on certain trannies because of high mileage. but generally I don't trust his judgement anyway.

oh yeah that's fine. That's not a flush, that's just fluid replacement. As long as it's not pumping fluid in. That's actually the best way to do it because you mix a bit of old fluid with new fluid, so you're not chaning the atmosphere in the trans too much.

Exposing a trans to air isn't harmful. Most trans fluids today have antioxidants so that no part in the trans gets rust. Electronic transmissions have vents apparantly. So your trans is already getting oxygen as it is.

sorry if that was confusing the way i wrote it.
a fluid change is never bad unless done inproperly.

a flush on the other hand can and usually does end up doing more harm than good due to the fact that when the fluid is forced out and stirred up inside the trans, very small metal shavings and such get stirred up from where they have settled and find their way into places where they can do some harm.

its more of a problem on older trannys, but i still wouldnt reccomend doing it.

ya know, with people coming behind you and posting nonsense like that, the hell with it, I have better places and better ways to spend my time. well nobody is forcing you to come to this forum.
believe what you want, but trans flushes can do harm, and i was informing the poster of that fact.


I was talking to a mechanic (buying some parts) and he said that is the best thing you can do to a trans since it doesn't expose it to air and it's a full fluid exchange, better than a drain and fill.
i'm not familiar with the T-tech process, but if its only powered by the normal flow of fluid, then it seems ok.

Thanks for the info guys. I understand why heavyJ was upset, thats the reason this question exsists, statements without explanation. GreyGoose006, i see you added in more info now, thanks.
I think im going to do a fluid change in both of mine,

99 Chevy Venture 111k miles fluid never changed,

94 Chevy C1500 195K most likely changed because it looks like the tranny was replaced.
Fingers crossed.

Make sure to reset the car's ECM so that you re-teach the transmission how to shift. THe new fluid surely changes things a bit.

Make sure to reset the car's ECM so that you re-teach the transmission how to shift. THe new fluid surely changes things a bit.
How would i do this. Would disconecting the battery then reconnecting it reset it?

Make sure to reset the car's ECM so that you re-teach the transmission how to shift. THe new fluid surely changes things a bit.
i've never heard of doing this.

Make sure to reset the car's ECM so that you re-teach the transmission how to shift. THe new fluid surely changes things a bit.

changing the fluid won't make a transmission "forget" how to shift.

that's like saying if you change the oil you have to re-teach an engine how to run.