Change transmission fluid, it will harm it

[marioc89]

I seriously need input on this. I went to the dealer today to inquire about getting my transmission fluid changed. The guy asked me my mileage, told him, he said he wouldn't recommend changing it because it will cause my transmission to fail. He said it's best to leave it if it's not giving me any problems. Anyone agree with him and how true is it he's saying?

[barnaclebob]

I had mine changed at 60k, maybe 90k?, 140k, and no problems since, currently only at 146k though. To my knowledge the pan has never been dropped and filter screen replaced. What is your year, mileage, how long has it been, and does the transmission have any problems right now?

The thought behind this myth is that a flush will disrupt a bunch of sediment or metal bits that will then cause a lot of wear or fluid channels to clog. However if your transmission already has metal bits big enough to cause issues in the fluid then its already on its last legs.

I don't think there should be any issues doing a drain and fill. If the drain plug is magnetic and it only has a metallic sludge (no chunks or shavings) then you are fine.

[atraudes]

barnaclebob nailed it. I'll just supplement that with the recommendation that you install a Magnefine filter. Installing it and running it for a while before you do a flush/drain will greatly reduce the quantity of particulates floating around the transmission that could cause a problem when you exchange fluid. They're an excellent idea, regardless.

[marioc89]

Ok. Great ideas. I have a 2000 with 244,XXX on it. I inherited from my sister. Before that she bought it second hand as well. I'm not sure if it has been changed, I just wanted to do it to cross it off my to do list with it. The transmission is fine other than when its cold it takes a second to go into drive but once warmed, it'll go in. I was gonna change the fluid and add some Lucas oil to it to give it longevity. But I'm not having any slipping issues or what not.

[marioc89]

And I was looking to buy that filter but don't see where to purchase it.

[atraudes]

I bought mine on Amazon, but I think most auto parts stores carry them. Just be warned that I bought one with 3/8" size fittings on it and they were too big for the hoses I had. I ended up getting one with 5/16" connectors and it fit perfectly.

[marioc89]

Ok. Cool! And the name of them are called a magnefine filter? If I get it out the parts store, will the clerk know what I'm saying with that name?

[atraudes]

Exactly, they should know what it is. Here's the product link.

[Buzzman]

This is just me, but every vehicle that I did a fluid replacement or flush on, the trany failed soon after.
It has put me off changing the fluid in my 2002.
It still runs and shifts perfectly, even with 300,000 kms. on it. I'm leaving it alone.

[barnaclebob]

This is just me, but every vehicle that I did a fluid replacement or flush on, the trany failed soon after.
It has put me off changing the fluid in my 2002.
It still runs and shifts perfectly, even with 300,000 kms. on it. I'm leaving it alone.

Why did you do the flushes at the time you did them and how many cars are we talking? Were the cars due and still shifting perfectly or did you notice something weird and decide to flush the fluid to see if it helped?

[Buzzman]

Why did you do the flushes at the time you did them and how many cars are we talking? Were the cars due and still shifting perfectly or did you notice something weird and decide to flush the fluid to see if it helped?

3 different cars were affected.
This goes back a little while, so maybe things are different now, but at the time, I was pretty peeved off.
The first one was a Dodge Grand Caravan.
I know now that the transmissions on these things have a bad history, but at the time I did the fluid change, I thought it would be a good idea, as a preventative maintenance thing. Would the transmission have blown anyway? I'll never know.
It was a catastrophic failure. Driving down the highway when it let go. I had my foot on the gas, and the engine over revved before I knew what happened.
The resulting high revs with no load blew out my block heater plug, and blew out all the antifreeze in about 3 seconds. Huge ball of steam. Scary stuff.
End of transmission. Engine was OK. I shut it down right away.
The second car was a Ford Escort. A month after fluid change, I lost all gears except first. Transmission was repairable, but I got rid of it after I fixed it.
Third vehicle was a Ford Windstar mini van.
Got talked into doing a transmission flush at a quick lube station. Will I ever learn??
Transmission started acting up within a week, slipping gears, slow shifting, or no shifting.
Took it to a specialty shop and they told me it was shot.
I wanted to get rid of this POS anyway (I hated that van), so I took it to my Nissan dealer and traded it in on a 2002 Pathfinder.
I never fixed the transmission, and on a quick 10 minute test drive by the dealership, it didn't slip. Whew.
Got the trade in value I was looking for, and thanked my lucky stars. I never looked back.
Still driving the Pathy.

[barnaclebob]

Hmm hard to tell if it was just crappy domestic transmissions or related to the fluid...

[cr4west]

Perhaps there are two paths here:
1. regular maintenance meaning around every 75,000 transmission fluid change with a new OEM transmission filter. Did not flush with any weird fluids, only changed the transmission oil.
-OR-
2. Zero or spotty maintenance service history unknown, lost.

For what it is worth I changed transmission fluid every 75k and now have 206,000 miles on the QX4 with the original jatco transmission. In addition we towed a 19' Searay I/O boat with it. I DO use additional external coolers, ford plate type. Heat kills these transmissions if you plan to tow anything.

Changing transmission fluid late in the game (125-150k miles) it may be a gamble. Almost ready to die transmissions often exhibit dark thick fluid contaminated with friction material from the steel disks and bands. This thick fluid may be what keeps it functioning because the accumulation of foreign material makes up for very worn tolerances. On the flip side thick fluid does not go through a blocked filter very well causing slow shifts or oil starvation.
So look at the fluid and see how burned or contaminated it is. Dipstick and while piece of paper works, look for black particles.

[marioc89]

So I see the next best thing to do is to install an in line filter and that's it huh? Wow.