changing old trany oil?

[plusinfinit]

Hey i have heared that if u have an old car over 100K miles that has an automatic trany you are not allowed to change the oil from the trany. I heard that the gears slip ? What is the big deal about changing the trany oil? How could it damage the trany?

[Steeb]

you should change it regularly as well as a new magnetic drain plug if they offer one.

[guyaverage]

"Not allowed" to change the oil...?

The theory behind that is when the oil is that old, it contains enough particulates that it actually helps create friction in otherwise worn-out bands and clutch packs. Its a great theory, I dont buy it personally. Anything with that many particulates to create enough friction to help a tranny from slipping probably has enough to seriously gunk up the valve body, bearings, and everything else in its path in the process.

I owned a Honda that had over 170,000 miles on its original oil before I changed it for the first time (I was the only owner, bought it new). At 290,000 it was still going strong, slip free.

If you decide to follow the advice of not changing it, on a Mazda automatic you can rest assured that at 120,000 miles or so you will be looking at a $1500 rebuild. Otherwise, put on an aftermarket tranny oil cooler, change the oil at regular 10-20 thousand mile intervals, and you'll do fine.

[Andrew_Pakula]

I believe that theory is correct because it happened to me a few years ago with my automatic.

It started slipping a little and not changing gears fast enough. So they changed the fluid.

It ended up making it worse. With the new fluid it started shifting extremely hard and within a few days it was dead.

My current Auto tranny has lasted me over 3 years now, in that time I have only changed the tranny fluid once about a year and a half ago because the fluid was smelling a little burnt. Since then I have checked the fluid regularly and it appears to be ok. There is no real good reason to change it unless the fluid starts to smell burnt, thats when you should change it.

[mitmaks]

Originally posted by Andrew_Pakula:
I believe that theory is correct because it happened to me a few years ago with my automatic.

It started slipping a little and not changing gears fast enough. So they changed the fluid.

It ended up making it worse. With the new fluid it started shifting extremely hard and within a few days it was dead.

My current Auto tranny has lasted me over 3 years now, in that time I have only changed the tranny fluid once about a year and a half ago because the fluid was smelling a little burnt. Since then I have checked the fluid regularly and it appears to be ok. There is no real good reason to change it unless the fluid starts to smell burnt, thats when you should change it.

maybe they didnt put enough back in or didnt put plug back in? believe me it happens a lot at places like jiffy screwbe.

[masonholmes]

I believe the, careful when changing high milage ATF rumor, at least with these particular trannies. The more known problem creator, (did they do this in your case Andrew?), is flushing a high milage tranny. This is somewhat different than just changing the fluid. I myself have changed my ATF at the 120,000 mark, with absolutely no probs - but I was too scared to try and flush it at the same time. I put Mobil-1 synthetic fluid back in, and a B&M Supercooler tranny cooler on, (the one rated for 19k GVW), and it's been absolutely great ever since. I now change at the 25k interval, and check the status/level of it when I think of it. Many different places will say different things about changing fluid. Many say do not ever change it, some say chagne it every 10k.. IMO, changing it about every 30k is no biggie, and it can't hurt to have fresh fluid/filtering, so why not? My opinion, change it, (don't flush), and replace with synthetic. Also, if you do not already have one, install a cooler. These trannies NEED an aftermarket cooler to survive their heat buildup, and it's a pretty basic install proceedure.

[masonholmes]

oh yea.. a problem seen with FLUSHING a high milage tranny is that of washing out old partical buildup around seals and stuff. It is said that this buildup helps to keep things kinda tight, and working as they should. If you flush, you wash these particals out and thus, parts have more play etc, which in turn leads to major problems.

[yuuki]

hey Andrew_Pakula i'm a little curious.. how many KMs did you put on it the past 3 years with that tranny?

[lakersfan1]

If you do change your fluid, try some Dexron 5. I just used some on my other Mazda with an auto, and it really helped with more positive shifts. Mercon 5's seem to all be synthetic blends, so they are a little pricey. But they seem to be a little thicker than Mercon 3, and are supposed to be backwards compatible with Mercon 3.

[Andrew_Pakula]

Originally posted by yuuki:
hey Andrew_Pakula i'm a little curious.. how many KMs did you put on it the past 3 years with that tranny?

In the past 3 years with my current tranny I have put somewhere around, appoximately 60-70k and it is still going strong.

In this period I have only changed the fluid once about 1 1/2 years ago because it was smelling slightly burnt. Last time I checked the fluid was in late fall and it still seemed ok.