Transmission fluid change

adsm08 said:

Jukkak is spot on. The relationship between flush and destruction is a case of mistaken causality.

A lot of techs who don't know much about transmissions (I am included in this group) will get handed work orders for poor shifting, or some other fairly minor issue, recommend flushing the trans because new fluid cleans and lubricates better, and often poor shifting is a sign of something getting stuck in the valve body. The customer approves the flush thinking it is a fix-all kind of thing, rather than a "Well let's start by getting your basic maintenance up to date" thing. Then because the issue was more serious it actually breaks a little while later, after it seemed good. They then assume, because all customers think this way, that the flush must have damaged something inside the trans. So they go tell their idiot brother in law, who tells his idiot co-workers, and pretty soon the whole world thinks that regular maintenance, especially if it was overdue, is going to break their car.


The truth of the matter is if you change your fluid and the trans breaks right away it was on borrowed time already because the dirt was all that was holding the guts together.

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This is very true. Many think changing the fluid/filter is what kills the older transmissions that have been neglected. Usually if the transmission is in good working order, changing the fluid and filter isn't going to be a problem. Its those old neglected questionable transmissions that have shifting issues already that will most likely suffer a failure due to changing fluids. The fluid picks up debris from the transmission over time and changing that fluid can cause the transmission to start slipping and not shifting because the new fluid is more slippery so parts start slipping rather than working as they should...worse is doing a flush because that will usually break up stuff and send it throughout the transmission causing further problems...its just best to leave a questionable transmission alone.

In a transmission that is functioning properly that you don't have a record of service on I'd do just a fluid and filter change and let it be. Far less failure problems from changing fluid and filter compared to flushing from what I've gathered over the years.

If its working now a simple fluid and filter change should be just fine.

As someone who ran a chain of 13 transmission shops for 7 years for three different companies, I feel qualified to chime in.

Some of what is above in previous posts is correct. My guess is that it has been changed before. 177k on stock fluid would be black sludge and I doubt you would be driving as it would have failed years ago.

The whole changing fluid making things worse is not a myth, however its not because the fluid makes things worse, it just reveals otherwise masked problems. Put it this way... if you change your fluid and it suddenly dies, it would have died next month anyway. The real reason is because ATF dissolves things. It is a common misconception that ATF has more detergents than motor oil, but that isn't always the case. It actually has less detergent and a higher solubility. Think of it this way. Let's say you have a pint of salt in a bowl and add a quart of water. The water will dissolve some of the salt but become saturated before it dissolves it all. Now pour off half of the water and refill with fresh. It will dissolve some more of the salt. When you do the same thing with ATF, it will wash some of the carbon in the clutches that has been burnished into it over the years. If the clutches are fine, you have no worries. If they are down to their last legs, you might have slipping.... but they were on their last legs anyway and it would have died soon regardless.

Where you get into trouble is if you go too long between fluid changes, the reduced lubricity makes temps higher which converts more of the clutch material to crispy bits and therefore more gets washed away at the next fluid change. The secret is more frequent changes which prevents clutch crispyness.

Here is what I always recommend. Pan and filter. This will replace about 1/3 of the fluid, give you an opportunity to see what debris is in the pan, and give it a fresh filter. In the 2500+ transmissions my shops did this way, exactly one (a Toyota A340)displayed problems with slipping afterward. Upon tearing it apart, most of the friction material was completely missing from the 1st and 2nd clutch packs. It was near dead anyway.

Do a pan and filter, you'll be fine. I recommend against a full flush in almost every case. It is overkill. Just do a pan and filter every 60k or so. I had a 4R100 that went 357k that way and still shifted great the day I sold it the truck.

Shran said:

Using this logic, I will never again change my engine oil, coolant, brake fluid, or power steering fluid.

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whatever...

91stranger said:

whatever...

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Take that!

I changed the oil and filter for Powershift transmission that had about 80k miles on it, the used oil was dark coloured and I believe it was the first oil change for that transmission. The oil change interval for that transmission is 38k miles here in Finland. This was about six months ago, the car hasn't returned to the shop at least yet.

91stranger said:

whatever...

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Burn!!!!

No one burned me. If you all think I'm gonna get burned by someone on a forum then you are wrong. I've got 4 kids, wife, full time job, a million side projects outside of car maintenance.

Whoosh.

Didn't think you had car maintenance. Well as far as the fluids anyways.

I agree with Curtis,clean fluid never hurt a transmission any more than clean oil hurt an engine.I was the trans tech at a dealer for years,have had 80 plus vehicles and 1 transmission failure caused by my 17 year old driving habits.

I hate this topic. I've done a full tranny fluid swap on at least 25 high mileage cars. Every time I swear I heard the tranny say "thank you Woody, I needed that". Never had an issue. I call this the "My 1967 Powsrslide blew up after a tranny fluid swap urban legend"

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With high miles if it hasn't been flushed or changed, it's best to drop the pan and change the filter but a flush is a bad idea because that can break some stuff loose and the tranny will go out in short order. Had it happen on a Lincoln I used to own even though the fluid had been flushed somewhat regularly (my dad bought the car new). You could install a drain plug in the pan while it's out and drain and refill it once a year.

JohnnyO said:

With high miles if it hasn't been flushed or changed, it's best to drop the pan and change the filter but a flush is a bad idea because that can break some stuff loose and the tranny will go out in short order. Had it happen on a Lincoln I used to own even though the fluid had been flushed somewhat regularly (my dad bought the car new). You could install a drain plug in the pan while it's out and drain and refill it once a year.

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The punctuation alone is reason enough to follow this advice.

FWIW, I just changed my fluid on my '03 Ranger Edge 4x4 with 233,000 miles on it. Our company bought this truck with only 20,000 miles on it many years ago. It's been put through hell and I don't think it's ever had it's trans. fluid changed. It didn't look horrible but definitely not pretty and it smelled like old trans fluid. 4th has been a little finicky sometimes shifting in a little hard. I know I am destined for a factory remanufactured trans at some point but I figured this would help. I popped the pan off and was surprised to only find very tiny almost microscopic metal on the magnet, there was a fair amount built up over the years but none of the deposits were actual fragments just a descent build up of tiny tiny metallic powder. I replaced the filter with a WIX filter.

When I put the fluid back in, I added a bottle of Lucas Trans. Fix along with the correct fluid. I also changed the transfer case fluid and diff fluids at the same time and the truck drives just fine and shifts smoother. 4th still feels a little weird every now and then but it gets up and goes just fine. I'm not a fan of DIY flushes but fluid changes on everything are fine by me.