Hypothetical transmission question

[mdboulier]

If I never change the fluid in automatic transmission, what’s the probability that it’s ultimate death is attributed to a component that broke down or degraded due to a poor lubrication schedule?

On average how much longer would you expect a modern automatic transmission to last with a proper drain and fill with OEM fluid done every 30k? Assume no serviceable filter.

 

[demarpaint]

Tough call, you didn't describe how this hypothetical vehicle is driven. A lot of highway driving is going to positively impact how long the transmission lasts, making 30K services not as necessary as they would be in a car driven in pre-CV-19 NYC traffic.

 

[mdboulier]

Tough call, you didn't describe how this hypothetical vehicle is driven. A lot of highway driving is going to positively impact how long the transmission lasts, making 30K services not as necessary as they would be in a car driven in pre-CV-19 NYC traffic.

Good point. Maybe how much longer would it last in terms of percent, like 50% longer. My vehicle use is mostly suburban which is a nice mix of both. I drive like a grandma 98% of the time.

for others, just state any assumptions you make

 

[slacktide_bitog]

Most cars go to the junkyard (for reaosns unrelated to the transmission) on their factory fill ATF and never have it changed.

 

[SoNic67]

Did you do a survey?

 

[apham8]

I believe the specific answer you are looking for is in too broad of a question. Perhaps narrowing down what type of vehicle (make, model, year).

The specifics of driving in suburban city/hwy mix helps, as well as your driving style. But certain vehicles, such as Hondas of specific models/years, are notorious for having transmission go bad. And not necessarily because of ATF fluid changes.

Essentially, slacktide_bitog hit the nail on the head. Many vehicles, if not the vast majority, do not ever have their ATF changed yet they never have transmission issues. While other vehicles, perhaps a very particular few, can have regular ATF fluid exchanges and still have transmission failures before 200,000 miles.

 

[SZR48207]

My understanding is that all auto trannys have friction discs that eventually wear out which will cause slipping. No amount of religious fluid changing will prevent this. At some point in its life, a factory installed transmission will have to be removed and disassembled in order to be put back into service.

But my other understanding is that ATF has additives that protect from wear, so fresh fluid may at least prevent accelerated wear.

How does this all add up when you've got a car with 200K miles? No idea.

 

[MattPersman]

Add packs wear out, fluid wears out causes slippage earlier so new fluid should at least in theory give you the best possible chance of lubrication success

A hard part can fail randomly at anytime New fluid or not

 

[el Nuke]

Very difficult to answer with any certainty. Some transmissions will be more prone to failure without regular maintenance than others, and others will benefit much more from regular maintenance as opposed to none. Not to mention geographical location and its climate playing a key...

 

[SZR48207]

Here's something to throw into the mix as well. My old F150 with the V6 and 4R70W started slipping at around 120k miles despite me being very good about changing out the tranny fluid. I took it to a well respected tranny shop in my area and the owner said he was not surprised it was slipping since I had the V6. His reasoning was that this particular combination (V6 + Auto) put more stress on the transmission since the engine frequently needed to downshift to keep up, and that a V8 + Auto in the same truck tended to make the transmission last longer between rebuilds.

Still not sure what to think of that some 10 years later, although I can see where it's coming from.

 

[CharBaby]

In my experience with automatic trannies, it's a hit or miss. Those with known quality/longevity gave me issues even with good maintenance e.g., ATF & filter/screen changes. And those with known high failure rates gave me no problems even when not so well maintained.

 

[SoNic67]

Discs can slip (and get worn) when not enough pressure is delivered by the oil pump to allow correct functionality. Oil pressure can drop because of various restrictions in the hydraulic circuit, build up of varnishes for example. Changing oil per manufacturer recommendations eliminates that.
I have now 5 vehicles in my household that I maintain and 3 of them are almost 20 years old, with about 200k miles. Two are Ford, one Hyundai. Because I change the transmission fluid at about 40k miles they are still shifting perfectly. I know lots of people that sent their Taurus at junkyard, without having once do a transmission fluid replacement, and they didn't make it past 100-120k miles of heavy city traffic. They blame the manufacturer when is their fault of not maintaining the car.

Even manufacturers recognize that there are different regimes that cars are used in.
A car that is used mainly on highway, sitting mainly in the top transmission gear, will have the fluid last "lifetime".
A car that is used mainly in stop and go traffic (city/urban environment), at high ambient temperatures (Southern US), constantly shifting gears, will require more often fluid changes.
Traffic only got worse in the last decade. Summers seem to get hotter. I am curious what will be the live expectancy of newer cars with the mentality that "transmission fluid is lifetime".

My old F150 with the V6 and 4R70W started slipping at around 120k miles despite me being very good about changing out the tranny fluid.

I have a 2001 Ford Explorer with the V8 5.0L engine and the same 4R70W transmission. I do drain/refills at about 40-50K miles (added a pan with a drain bolt) and my transmission is fine at 190k miles. What is different from your V6 is that my Explorer came with "Towing Package" that includes an auxiliary transmission cooler. It also has an engine oil heat exchanger. I never towed anything, transmission temperatures are seldom past 175F (OBDII reader) - only when I am stuck in traffic in days that are 98F or higher. No air flow over the aux cooler when stopped.

I had also experienced transmission temperatures up to 220-225F in my Mercury Sable in the same conditions (very slow traffic, hot days). That was happening when I was trying to save gas by not using the A/C (open windows). Big mistake! Once I started the A/C, it automatically kicked in the fans, and transmission temperature dropped at about 190F. That car has about 200k miles now, same oil change regime (I have added a pan with drain plug on that too), use A/C in summer, even if is at the lowest fan speed.

 

[mdboulier]

My original curiosity was around the economics of transmission fluid maintenance. Seems like most of us DIYers find it easily justified to buy a few quarts of atf every so often. I’m not sure it’d be worth paying shop prices frequently.

Add onto that the complexity of, if a trans dies at 100k it’s unfortunate but usually economical to justify repair vs replacement of vehicle. But if one dies at 160k or 200k, the repair cost vs vehicle value may not be justified depending on the owners strategy.

The default economical recommendation for a DIYer seems to be doing the relatively inexpensive fluid changes to prolong trans life as long as possible. But perhaps someone paying $180 shop price for trans fluid drain/fill is wildly overpaying for this “insurance.”

what would you tend to recommend to people who don’t work on their own cars but want to drive them till the wheels fall off?

 

[SoNic67]

I don't know...
I am one of those guys that maintain their cars maybe too long. I always did a couple of drain and refills to refresh the oil, and at higher mileage even started to add Lubegard in it (only additive that I trust).

Now I have accumulated 5 functional cars in front of my house (3 drivers that mostly work from home now), and 3 of those cars are from 2000-2001 with close to 200k miles. On original engine and transmission. I can't sell them because people think they are "worth nothing" at that age and mileage. That is based on their assumption that no maintenance was done to them (like 90% of the cars on the road). Those cars have better shocks, tires, brakes, timing belts (where applicable), water pumps, tensioners, LCA's, motor mounts, spark plugs, injectors, fuel pumps than most of the 7-10 year old cars on the road because I replaced them. I see newer cars on road bouncing up-down with blown shocks every day, or with the engine blowing clouds of smoke when taking off (4 cyl cars usually), with serpentine belts squealing... people don't care.
I can't crush them because I have this stupid thing against destroying functional objects just because are old. I'm a hoarder?

Maybe in the end it doesn't matter. Maybe my approach is wrong, and cars should be treated as disposable items, three-five years and done. Maybe we should be forever in debt paying for the newest toys...

 

[demarpaint]

My understanding is that all auto trannys have friction discs that eventually wear out which will cause slipping. No amount of religious fluid changing will prevent this. At some point in its life, a factory installed transmission will have to be removed and disassembled in order to be put back into service.

But my other understanding is that ATF has additives that protect from wear, so fresh fluid may at least prevent accelerated wear.

How does this all add up when you've got a car with 200K miles? No idea.

True. It's still a good idea to get that fluid containing the wear metals out so it doesn't plug something up that aids in the shifting/operation of the transmission causing additional accelerated wear. Most transmission filters aren't very good at filtering, and the magnet/s only catch ferrous metals, there are other contaminants not filtered out or caught by the magnet/s that can cause damage. ATF also degrades from heat, and can cause varnish which eventually will mess with how the solenoids function. So imo servicing an automatic transmission is a good idea.

 

[mdboulier]

I agree there is something about scrapping a car that seems unnecessarily wasteful. Beyond the numbers of it.

I follow a few F.I.R.E. groups online and consume some podcasts like Choose FI (Financial Independce Retire Early). There definitely are people, a vast minority, who are not focused on consumerism and want to optimize their auto cost/mile.

In general, the advice among that crowd is to buy a 5-10 year old used Honda/Toyota and drive it till ya scrap it. But there’s a wide range of application/deviation based on personal preference and income. My brain was contemplating what maintenance best practices would you stack on top of that advice in order to further reduce costs and or avoid breakdowns.

learning how to have your trans fluid serviced (DIY or learn what to ask for and what to avoid) and learning how to change engine/cabin air filters struck me as things with high reward. With readily available cheap and instant engine oil changes that last 10,000 miles I wouldn’t recommend anyone start there unless they’re doing it for enjoyment which most of us are who choose to DIY.

 

[reddevil]

The nissan qashqai (rogue) was introduced to Australia from 2014. I got the 2015 model (2.0 FWD). It has the "lifetime" transmission fluid. It it one of the best selling SUV. I had a home made dipstick to check the fluid since it just had the fake transmission cap.

After 30K miles, the fluid is still new , almost transparent against white napkin. The car is mainly used for short distances, about 5 miles each way suburban driving, 4 days a week. So is this considered severe usage?

The models are all assembled in UK.
Also there are numerous articles about fitting aftermarket cooler but the models here comes with the 4 port cooler, i.e. it uses radiator water to cool the transmission fluid.

Similar to the one here:

New Upgraded 4 Port CVT Transmission Oil Cooler compatible for Nissan Rogue Juke 2011 - 2013

Buying for performance CVT Transmission Oil Cooler Kit Fix Upgrade compatible for Nissan Overheating 21606-1XF0A, welcome to choose auto parts in maxpeedingrods.com with best cheap price. Free shipping and Warranty.

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The cooler comes standard. NS-3 compatible fluid is hard to find. I guess maybe owners seldom change the fluid either by themselves or by independent workshop and the factory filled fluid is really "lifetime". I will continue to check every few months to see if fluid is getting dark before changing.

Btw for those nissan owners, "How to" remove the dipstick cap videos shown on youtube are wrong i.e. you do not insert screwdriver from the top to remove the cap.

 

[SoNic67]

I got my Kia Soul and Toyota RAV4 used, both with about 70k miles. Drained fluid was very dark. I don't know how they were used, but heavy traffic here means driving 30 miles in one hour, in ambient temperatures of 38C.
Those are both classical automatic transmissions (no CVT or dual-clutch).

 

[UnderDawgAl]

If I never change the fluid in automatic transmission, what’s the probability that it’s ultimate death is attributed to a component that broke down or degraded due to a poor lubrication schedule?

I don't know the exact value, but the probability is certainly much lower than if the engine oil weren't changed.

Modern cars are really technological wonders. How many Fords, Chevys, or Dodges from the 1970s lasted 200K miles? I remember my dad rebuilding the engine of our '77 Plymouth Volare station wagon (cursed wretch of a vehicle) when it had only 80K miles on it. Today, models from all makes routinely go 200K with minimal maintenance, and often with no major maintenance.