Changing auto trans fluid myth?

[Ether-D]

I have a real hard time believing this, but I've heard on many occasions that if you wait too long to change your auto trans fluid, it will wreck the trans when you do change it. Supposedly, it's better to just leave the old muddy fluid in there. Has this actually happened to anyone?

I just did my Tbelt, and when i removed the trans lines from the radiator, the fluid that came out was naaaaaaaaaas-ty. I want to change it. I just bought this car, so I don't know how long it's been since it has had the trans fluid changed.

Bring on the input, and thanks in advanced.

[jlevie]

What can happen if fluid and filter changes have been deferred too long is that the fresh fluid (loaded with fresh detergents) can cause deposits to break free and clog valves.

What I would try, in an attempt to prolong the life of the transmission, would be to change the filter and mix about half of the old fluid with fresh. Drive the car for at least 500 miles and repeat several times until essentially all of the old fluid has been replaced. Hopefully the lower levels of fresh detergent and time will slowly dissolve the crud.

FYI: For best life, the filter and fluid should be changed every 50k.

[Ether-D]

Thanks so much. That makes sense.

So every 50k miles? That means it can only be 150k miles over at the most, great!

[pantelones]

Well it looks like I just (maybe) fucked up my transmission.

[Jaxx_]

The idea behind this is that the old fluid has enough particles that they act as a friction modifier and stop worn parts from slipping. I've never heard of it actually happening, and the only time I've heard it could be an issue is if you already have a lot of metal in the fluid.

in which case, it's probably time to look for a new transmission.

[TimKninja]

in which case, it's probably time to look for a 5 speed swap.

Fixed

I've heard this as well. Ive also heard automatics aren't really supposed to last over 150k Miles. I would change it anyways.

[Ether-D]

When I did the T-belt I lost about 2.5 quarts and added fresh back to it. I'll probably drive for a few weeks and then change it all. You can never really get it completely empty, right? So I'll change it, and put a fresh filter on and hope for the best. If she goes out, how much does a 5 speed swap run for the iXs? Just parts, I can do the labor...

[Jaxx_]

there's always going to be a lot in the torque converter, it's a matter of flushing it, it's difficult to replace all the fluid without a machine.

[z122643]

I've got a friend with an 89 iX auto. 225,XXX miles. Guy is seriously OCD! Bought car with ~60K has done fluid and filter changes on it every 50K never had any transmission problems.

I've done multiple fluid and filter changes on E30s. Here's four examples of changes WAY past 50K

1: 325is 88, fluid change by BMW at 60K then driven to 175,XXX. Did a full fluid and filter change. Car then driven 3K and repeated process. No issues.

2: 318i 90, fluid change by owner at 75K then driven to 150,XXX. Did a full fluid and filter change. Car made at less then 500 miles before failing to shift correctly. Did another fluid and filter change in which the filter (the new one I installed) was clogged. No issues after second change

3. 325i 90, fluid never changed to 160K. Decided after perviously car listed above to try the "50/50" approach. Changed filter and 50% of fluid. Drove it enough to cycle through gears, then did a complete fluid and filter change. Filter (the new one I installed) came out nearly clogged. No issues.

4. 325iX 89, fluid never changed to 135K. Did full fluid and filter change. Drove for ~4k then started experiencing shifting issues. In this car the valves became clogged and "professional" help was needed to service the transmission. (NIGHTMARE)

I would say that example #3 is how you should proceed with your transmission. A "50/50" to start then repeat the process with a full change.

*continuing to drive without any change WILL result in RIP transmission*

http://www.r3vlimited.com/board/images/smilies/blowingup.gif

Fixed

I've heard this as well. Ive also heard automatics aren't really supposed to last over 150k Miles. I would change it anyways.

[Ether-D]

Great advice, and thanks for the examples.

[Ryann]

2: 318i 90, fluid change by owner at 75K then driven to 150,XXX.

What.