when/if to change trans fluid? miles or years?

[columnshift]

I have to be honest, prior to reading on this board i'd generally not even been aware that transmission fluid in an automatic would need changing... but then thats a habit inhereted from a father and cars didn't last as long in his day. So just like this site has opened my eyes about synthetics and better coolants and stuff, what is the distilled wisdom of changing transmission fluid in vehicles where it WASNT mentioned in the manual or even something to be aware of at the time? I'm wondering if all those things I heard about engine oil, especially 'clouding points' in cold climates and similar if it applies the same to/degrades transmission fluid in similar fashion... possibly meaning different recommendations for yearly freezing climates vs warmer ones too.

Like i've got two old Chevy vehicles (a caprice and a pickup, tho very few miles on the pickup) 1990 and 1991 with the same TH700R4 in them. I'm not even sure if either were made to have fluid changed, and I wouldn't be surprised if the original 27 year old now fluid is still in each - i'm 95% sure it is because it hasn't leaked.

I'm wondering whether driving with that fluid is in any way 'bad' or if it's definately worth the effort to drop a pan and mess about with it - and how much of a priority that should be. (since i'm trying to just get either of the vehicles up and running again, after multiple years of unfortunate sitting due to a TBI fuel problem in each, and i've spent my discretionary income on a car I screwed up meant to be a daily driver so it's down to emergency cash only until I can work it off in 6 months) Like could it wait until spring if it should be done, or does it need to be done at all, or am I damaging the vehicle slowly with every drive like a fool if I dont...


Yet i'm more curious on just what are the generally recommended principles? The above are just examples... instead of asking for every other car in the future, i'm curious what Best Practices should be for vehicles with no recommended interval, or for whom changing it might even be a PITA/not designed for by factory to do.

 

[SubieRubyRoo]

First off, I would NEVER force-flush a transmission... fluid exchanges are plenty. Drain & Fill, drop the pan & change the filter, etc... those are OK.

Changing time limits? My personal limits would be 3 years or 50k; this is likely a little overkill, but have you checked rebuild prices lately on transmissions?

If the trans isn't already slipping, a little longer is not likely to cause any "damage". Change the fluid (and filter if you can drop the pan), and if it's an electronic transmission be sure to disconnect both terminals of the battery to force the TCM/PCM to relearn the shifts after the fluid is done. Once you clear 100k total miles, if you have a notoriously picky transmission (especially if fluid changes are easy), I would up this to 30k fluid changes. My Odyssey is one such beast with tons of trans issues, so every other oil change (around 20k or so) I drain what comes out and refill with fresh fluid; about 3.9 quarts. This still works out to an entire fluid exchange roughly every 50k miles, and has kept my tranny going strong long after the typical Odyssey experience. $17/gal every 20k for Maxlife ATF is super cheap compared to $4k for a new tranny!!

 

[Kawiguy454]

pull the dipstick an look/feel/smell the fluid. Bright cherry red is good brown dark and burnt is bad. drop pan and change fluid and filter and don't worry bout it. I used M1 fluid in my 02 F150 and it is still humming along over 200k miles with my kid driving it.

 

[CT8]

With their age I wouldn't worry about it save the $$$ for new vehicles.

 

[working_title]

I typically don't buy cars that have less than 50,000 miles on them, and I have always drained/refilled the fluid and replaced the filter when I got the car. I've never had a transmission problem either, but that isn't saying anything.

Even on cars with low (50-60k) miles, every single pan I've dropped has had magnets completely covered in fine metallic particles. I do it for peace of mind, but in your case I'd definitely swap the fluid due to age.

In all of the older cars with higher mileage and old fluid I've noticed a dramatic improvement in shifting once the fluid is swapped. A 1994 Camry with 318k when I bought it shifted much better, and a friends 91 Civic (which was abused) also shifted considerably better after a drain and fill this past year.

 

[CKN]

Originally Posted by SubieRubyRoo
First off, I would NEVER force-flush a transmission... fluid exchanges are plenty. Drain & Fill, drop the pan & change the filter, etc... those are OK.

Changing time limits? My personal limits would be 3 years or 50k; this is likely a little overkill, but have you checked rebuild prices lately on transmissions?

If the trans isn't already slipping, a little longer is not likely to cause any "damage". Change the fluid (and filter if you can drop the pan), and if it's an electronic transmission be sure to disconnect both terminals of the battery to force the TCM/PCM to relearn the shifts after the fluid is done. Once you clear 100k total miles, if you have a notoriously picky transmission (especially if fluid changes are easy), I would up this to 30k fluid changes. My Odyssey is one such beast with tons of trans issues, so every other oil change (around 20k or so) I drain what comes out and refill with fresh fluid; about 3.9 quarts. This still works out to an entire fluid exchange roughly every 50k miles, and has kept my tranny going strong long after the typical Odyssey experience. $17/gal every 20k for Maxlife ATF is super cheap compared to $4k for a new tranny!!


This (force flushing) continues to perpetuate a "Internet term" that is incorrect as to how a so called "flush" works. As a matter of fact-just google how a modern "fluid exchange works' since you really don't know. I'm tired of explaining it.

 

[Linctex]

I have never, ever, ever ever in my life changed transmission fluid due to "age".

I have no reason to think ATF fluid "ages".........

I have always done "the look & the smell" test - and I've never gone wrong with that.

 

[HangFire]

In general, I guess the correct answer to this "when" question involves some formula of:
1. sustained temperatures
2. peak temperature
3. particle loading

People that tow (race, climb mountains, etc.) should replace ATF more often due to high ATF temps.

Some transmissions (I'm looking at you, Honda) require frequent ATF changes due to their design.

For the old but low mileage truck I would start an ATF change regimen, but I would start small, like a quart at a time, use a vacuum pump down the fill/check tube if necessary. Run it a while between changes. After several, drop the pan and change the filter.

For a high mileage vehicle, the transmission may die soon whether you service it or not. Many a transmission has died right after a big ATF change... I had it happen to me, back in the day... did the ATF change cause it? Who knows. Your best answer might come from a specialist who deeply understands that particular transmission.

 

[DONWATERS]

Those both take cheap dex 3. When I buy a used car, I always change the trans filter, clean the pan, and weld in a drain plug and then change it every 20k miles. Dex 3 is cheap. Not a full flush and clean, I think they cause more harm then good. Just the 4 or 5 quarts that come out, that way its gradual. A jug of walmart dex 3 is only $12.

The manual or guide probably says change every 100k unless used for towing, in a dirty dusty area or police taxi then every 20k?

 

[grampi]

For vehicles without lifetime fluid, I would recommend a drain, drop the pan and change the filter, and refill. If you have a newer vehicle with lifetime fluid that's under warranty, don't touch it. If you do and something happens to the tranny, it will void your warranty. If you have lifetime fluid and the vehicle is out of warranty, some say change it, some say don't. It's up to you...My wife's 2015 Sienna has a lifetime warranty on the drivetrain, so if anything happens to the tranny as long as we own it, the fix is on their dime, unless of course I change out the fluid and void the warranty...I'm not touching it...

 

[JeffKeryk]

Maybe 25K to 35K. That's what I do.
I can't hang with "lifetime fluids".
But that's just me.

 

[Lubener]

I have a Sunday driver that I changed last year. The fluid was last changed 25 years ago/ 40k miles. The drained fluid looked great and the filter was clean too.

 

[columnshift]

Originally Posted by Linctex
I have never, ever, ever ever in my life changed transmission fluid due to "age".

I have no reason to think ATF fluid "ages".........

I have always done "the look & the smell" test - and I've never gone wrong with that.


Bingo... yet we've got some great contrary reports here too. I agree with preventative maintenance and being safe, but with my nightmare trying to do a simple fluid change on my Accord where I think I just killed the car trying to extend it's life, it makes me re-consider whats worth it or not. Risk and cost isn't zero and now i'm literally living on credit cards for probably 2 months until I can save back the difference getting something with better MPG fixed and on the road again like my Saturn.

One thing that made me wonder was like for engine oil here in cold temperatures the talk about cloud points, being something that even makes "new old stock" ENGINE oil bad if it sits through a winter. (I still have CASES of 5w-30 inherited from a mechanic father that's been stacked up for over 15 years found behind stuff in the shed) So I wondered about the trans fluid. Or other fluids. (got 15 year old 'new old stock' coolant too, same story, "oh THATS where all dads mechanic fluids went to after the move!")

So I have a 29 year old truck with 21k miles on the vehicle, my dad garaged it and drove it generally only to church, but the last few it's mostly been parked and was barely driven even after I got it 5 years back cuz I didn't need it's 11mpg around town and right when I parked it it had had a running problem I couldn't diagnose that turned out to be fuel pump and idler something.. but now i'm driving it again since every other vehicle I have is broke. Fluid is nice pink, trans shifts as fine as any rough shifting truck of the era shifts. It's just 29 years old - i'm sure dad never changed it cuz of so few miles, but he never changed engine oil due to age either. I've also got a 28 mile old Caprice with more like 160k, that one's not driving right now (still trying to fix that as a 2nd vehicle is needed, i'm not the only one in the house needing a vehicle and sharing is hard) but when I parked THAT a few years ago, it was shifting fine too with it's 23 year old fluid.


I mean... I feel like I WANNA change both of them. Maybe next summer, when it's warm. AFTER I have my Saturn and at least one other car running again. So if I somehow recreate the nightmare of the Accord I just essentially killed trying to change it's fluid, so if I screw up again I haven't shot myself in the foot. (i'm aware that's a mistake i'm unlikely to ever make again, i'm just explaining why i'm gun shy rushing into more car work right now)

So it's more of a question I guess.. of what kind of increased wear might I be causing with 29 year old fluid if I drive it another 2000mi or 12,000mi or 22,000mi until then??

 

[grampi]

Originally Posted by JeffKeryk
Maybe 25K to 35K. That's what I do.
I can't hang with "lifetime fluids".
But that's just me.


I don't believe fluids are "lifetime" either, but hey, what am I supposed to do? My wife's Sienna has a lifetime drivetrain warranty (dealer provided) and the owner's manual shows no change interval for the tranny fluid. I'm sure changing the fluid would void the warranty, so I'm not changing it. If the tranny goes out while we own the vehicle, the dealer will have to repair/replace the tranny on their dime...

 

[wiswind]

grampi,
If you REALLY wanted to change the transmission fluid, having the dealer do it would most likely keep you in line as far as the extended warranty is concerned.
As you stated, it is not called for in your owner's manual....But, if you are doing some towing or other stressful operation, or just get a bug about changing it out, this is an option.

I have a 2016 Camry and just had the dealer do a transmission fluid "flush", which contrary to some statements is just a fluid exchange that gets closer to all the fluid changed as compared to a "drain & fill".
The fluid exchange cost $199 using their Toyota "WS" fluid. Paperwork said 8 quarts new fluid used. With past transmissions, a pan drop got around 4 quarts.
I'm at just under 50K miles and, like your Sienna, my manual does not call for a fluid change at all.....just a "check" at 100K miles.
In the past, I did fluid changes myself, including on my 2003 Sienna.
However, this newer transmission does not have a dip stick and the process for getting the fluid level CORRECT is involved.....so I had it done at the dealership.
I expect that I will be MUCH easier on the transmission with a car vs minivan (they tend to use the same transmissions) and no towing with my car, like I did with the minivan.