I understand engine oil gets contaminated by fuel and air and combustion, etc. However, transmission fluids are sealed and can not get contaminated, right? Do they lose their viscosity or separate or have anything happen to them to cause their needing to be replaced? I have a V6, rarely pull a trailer, use 4wd each month for trails, and carry kayaks on the roof a lot. In my manual up to 120k miles it never states that I need to swap out the fluids. Does towing cause the fluids to overheat and 'wear out' or lose their effectiveness?
What actually happens to transmission fluid to cause it to need to be changed?
- Thread starter Metzbower
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00328
Senior Member
I'm certainly no expert, but the ATF does get dirty, mostly I think from the clutch plate material breaking down. Heat also causes it to lose some of its properties.
Toyota basically recommends a change at 100K mi or sooner if you tow. Personally, I think that some marketing guy came up with that figure to make buyers think they are getting a vehicle that needs less maintenance.
Don't believe everything you read or hear. I would do a change between 60 & 70K. Its cheap insurance. I have about 62K on mine and will be doing a change here in the next week or so.
I think over the years car manufacturers have done a really good job of making their engines pretty bullet proof, transmissions....not so much. Transmissions can still be a little fickle and manufacturers need to turn their attention toward making them more reliable. A little maintenance goes a long way.
Just my .02 cents.
Toyota basically recommends a change at 100K mi or sooner if you tow. Personally, I think that some marketing guy came up with that figure to make buyers think they are getting a vehicle that needs less maintenance.
Don't believe everything you read or hear. I would do a change between 60 & 70K. Its cheap insurance. I have about 62K on mine and will be doing a change here in the next week or so.
I think over the years car manufacturers have done a really good job of making their engines pretty bullet proof, transmissions....not so much. Transmissions can still be a little fickle and manufacturers need to turn their attention toward making them more reliable. A little maintenance goes a long way.
Just my .02 cents.
SkylineGTRracer
New member
Heat, wear and tear, age, usage. All these things affect the viscosity and the lubrication properties. Fluids like these wear out over time, no matter what Toyota or anyone else tells ya. I have had my fluid changed as its cheaper than buying or rebuilding a trans. It does state somewhere in the manual that if you tow with your truck you should have it changed. Why Toyota says its 'lifetime' I have no idea but its stupid.
klennop
New member
I have a 2008, there are a couple manuals that come with the truck. One of them is a Scheduled Maintenance Guide.
60K, Special Operating Instructions, Driving While Towing, "Replace Automatic Transmission Fluid. Under the normal operating you are supposed to inspect it.
90K Under the normal operating you are supposed to inspect it.
120K, Special Operating Instructions, Driving While Towing, "Replace Automatic Transmission Fluid. Under the normal operating you are supposed to inspect it.
Doesn't it seem odd that if you tow, you should change it 2 times up until 120K but if you don't do any towing, you just leave it be. I am sorry but I am not buying that at all. I saw how mine looked with no towing at 60K, was it really bad, no, but I know I wouldn't have let it go to even 100K. Plus how do you check it without draining some to look at it when it is a sealed unit?
I would suggest even if you don't tow to do at LEAST do a drain and fill at the 60 and 120K. I know I will change mine completely out at 120K even with the minor towing I will be doing. Just that piece of mind, it is a lot cheaper changing out the fluid vs a new tranny.
message
Member
Especially towing puts lots of strain on a trans as well as producing extra heat. Thus the trans cooler(s) to keep the fluid temp down and prevent it from burning.
I remember one of my summer jobs we had a dodge truck we used for towing far too heavy of loads with. One day we lost 1st and 2nd out of it. Back at our shop you could hardly touch the trans pan it was so hot. When we dropped the pan all the fluid was burned and let me tell you that is one the worst smells ever!!!
I remember one of my summer jobs we had a dodge truck we used for towing far too heavy of loads with. One day we lost 1st and 2nd out of it. Back at our shop you could hardly touch the trans pan it was so hot. When we dropped the pan all the fluid was burned and let me tell you that is one the worst smells ever!!!
fourwd1
Moderator
Ignore the manual, if you wait 120K miles to do any trans service, you have a real good possibility of it crapping out. And by then it's out of warranty and could cost a couple grand to fix. H'mm, could that be their plan??
I'd have it flushed at least every 50K, for a $100 or so it's cheap insurance.
And external cooler couldn't hurt.
I'd have it flushed at least every 50K, for a $100 or so it's cheap insurance.
And external cooler couldn't hurt.
004Gunner
New member
I disagree with transmissions being a weaker component. I think they're one of the best built features of modern vehicles and don't require much attention at all to get 150k-250k miles out of them. It's more likely that people ignore transmission maintenance, especially people who have grown up with manuals as opposed to automatics. But like you said, a little maintenance goes a long way and I think transmission maintenance best demonstrates that mentality.
To the OP, heat is the single greatest concern with transmission fluid and anything that generates excess heat can shorten the life of fluid. Examples are (some already mentioned): stop and go traffic (especially during summer months), frequent cycling of torque converter, long or hard climbs at low speeds (off-roading), and towing.
Hungryhawk
Member
Due to my 2017 tranny needing replacement @48,000 miles I highly endorse a tranny fluid change before your factory warranty expires (either basic powertrain or Gold , Silver, Platinum extended service agreement).
A Flexlock torque converter solenoid and valve inside the tranny valve body malfunctioned. Dealer was authorized to replace complete tranny. The TC affect on drivability was "shudder/chatter".
This was caused by the Torque Converter Flexlock failing to release and created momentary braking. This ground up the TC clutch plates and gave fluid a beige color. Look carefully at the fluid removed from your tranny-it may provide a clue to the internals.
A Flexlock torque converter solenoid and valve inside the tranny valve body malfunctioned. Dealer was authorized to replace complete tranny. The TC affect on drivability was "shudder/chatter".
This was caused by the Torque Converter Flexlock failing to release and created momentary braking. This ground up the TC clutch plates and gave fluid a beige color. Look carefully at the fluid removed from your tranny-it may provide a clue to the internals.
Retired1951
New member
297,000 Miles on mine and never touched the transmission. no problems still going
Hungryhawk
Member
The Toyota "Car care nut" did a video on this topic. Seems the gunk in your old fluid is helping the internals work properly.
One reason the approved drain and refill only gets a partial change out of tranny fluid is this same core issue.
Your tranny benefits from some of the old gunk.
So your decision-do a small drain & refill or leave it alone.
Perhaps a oil analysis would give you more facts to make your decision. Use a syringe type extractor to get a sample out of your FILL plug.
You can replace exact same amount with new fluid.
Or, you can overfill the fluid a little-then do the precise tranny fluid temperature level check by opening the special overflow drain. Extra fluid drains out to the precise amount tranny needs at the precise temperature.
Weird process with lots of posts on the topic for our 4runners and also Tacomas that share same tranny.
One reason the approved drain and refill only gets a partial change out of tranny fluid is this same core issue.
Your tranny benefits from some of the old gunk.
So your decision-do a small drain & refill or leave it alone.
Perhaps a oil analysis would give you more facts to make your decision. Use a syringe type extractor to get a sample out of your FILL plug.
You can replace exact same amount with new fluid.
Or, you can overfill the fluid a little-then do the precise tranny fluid temperature level check by opening the special overflow drain. Extra fluid drains out to the precise amount tranny needs at the precise temperature.
Weird process with lots of posts on the topic for our 4runners and also Tacomas that share same tranny.
RobStoration
Junior Member
I just did a complete flush at 220K. It needed it. Looked like a Merlot. Lol.
I had nothing to lose as I was getting the 20-30 shudder. After the flush and 1000 miles it's just about gone. I may add a friction modifier to see what happens. I am happy with it.
I made a video of the process and I'll be posting it soon.
I had nothing to lose as I was getting the 20-30 shudder. After the flush and 1000 miles it's just about gone. I may add a friction modifier to see what happens. I am happy with it.
I made a video of the process and I'll be posting it soon.
scd969
New member
Let’s see the video! Mine has 255k and don’t think it’s ever been done
You're right that transmission fluid is in a sealed system, so it doesn't get dirty like engine oil. But over time, heat and normal use still break it down. The fluid deals with high temperatures and moving parts inside the transmission, which can cause it to lose its ability to protect and lubricate. Even without towing much, carrying kayaks and using 4WD on trails can raise temps slightly and speed up wear on the fluid.
Most manuals don’t list fluid changes until 100k+ miles, but that’s based on perfect conditions. If you plan to keep your truck a long time, it’s a good idea to change the transmission fluid around 60k–90k miles. It helps avoid problems later and keeps everything running smooth.
-yzrmzi
My sisters husband is a retired Ford transmission engineer. He says trans fluid has chemicals in it that help the transmission work properly. The chemicals can lose their effectiveness at 75k miles. Had a car that was acting weird, oscillating on acceleration. replaced the fluid about 75k, it worked fine.
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