How often to change ATF.....why?

[Donald]

Originally Posted By: ahoier
What gets me....on the topic of ATF and, the inherent "filter" change(s)......is how some of these quick lubes (Midas, Meineke, [censored] even Tire Kingdom....) offer "Transmission Flush" services.....they claim their machine can clean the gunk out/off of the filter.....now tell me how that works, without dropping the pan

I'm really curious....I understand the concept of "replenishing" the fluid, it basically slurps out the old fluid, and pumps in new fluid, until you got the proper concentration of "new" ATF.....but still, no filter change...? That just don't seem right I'd think the metals that were in there, are STILL in there, clinging for dear life onto that magnetic transmission filter.....correct..?


Basically they lie. But if you are the type of person to go to a place like that you would not know better. If you had some "goo" that was oil/grease based in the filter, the cleaner they add before the flush might clean it somewhat. But any particles will still be in the filter as they cannot be dissolved. Before there were flush machines, the quick oil change places would suck the old ATF via the dipstick, refill, add some conditioner and call it a day, never telling you they did not siphon out even half the ATF.

Another problem with the "use" of a flush machine is that the new ATF they put back in via the machine maybe some generic ATF that they add an additive to, to make it just right for your vehicle. I guess if I believe the flush machine cleans the filter I might believe their song & dance about using generic ATF and adding a special additive. Not to be confused with somewhat universal ATFs from Amsoil, etc).

 

[fpracha]

Originally Posted By: Zako2
One theory I have heard is that it's not that the fluid becomes bad after a certain period. The problem is that it becomes saturated with particles as a result of transmission wear that you don't want to have in the fluid. If that's the case, you need to change not only the fluid but also the fluid filter.

How frequently to change the transmission fluid depends on the car. I know that the Ford Taurus online community and others that use Ford's AX4N/AZ4S transmissions follow the manufacturer's fluid change recommendations religiously (flush everything and change the filter every 30,000 miles). These transmissions are relatively sensitive to neglect and have earned a bad reputation for being prone to failure and then an expensive rebuild. Part of the reason for this is the owners who never bother to change the fluid.


Is there also a time limit to the ATF fluid life or change interval other than the 30k miles number ?

 

[zeezee]

Originally Posted By: fpracha

Is there also a time limit to the ATF fluid life or change interval other than the 30k miles number ?


Depends on the car and transmission, and how it is driven. I change mine at 50-60k in one of my cars and it still looks new, but as mentioned previously there are wear metals on the pan magnet. It is probable that you can run them longer. My service manual implies that it isn't a critical thing for a vehicle that gets a lot of highway miles but is rather do it anyway since it is such a simple maintenance item.

And manual transaxles... Those can have a much longer fluid life if the manufacturer is to be believed.

 

[RF Overlord]

Originally Posted By: Donald
ATF wears out from heat, contaminants and shearing.
Short, sweet, and to the point. There's your answer.
Quote:
The major car companies wanted a competitive advantage over the others and used high quality ATF and said it never needed to be changed. Sounds good. It will get you to 100K with no change but its not the best for that expensive transmission.
Agreed 100%.

The manufacturer bases transmission "life" on their internal reports of in-warranty failure. To this end, any car that makes it past that point is no longer their responsibility. They are not concerned about the second or third owner, which is where many neglect-related problems show up. From a purely business standpoint, this is not wrong, and as an owner should I be concerned about what happens to the car after I sell it?

When I bought my second Marauder, I was the third owner and had only the maintenance history from the second owner. Because of this, I changed every fluid in the car as soon as I got it home. That was at 87,000 miles and she now has over 155,000. Would the transmission still be working perfectly if the fluid had never been changed? Maybe, but the $100 I've spent on periodic drain & fills since then is probably less than having the thing rebuilt....

 

[MuzzleFlash40]

My Mercury Grand Marquis's manual says to change it at 100k under normal conditions. NEVER, I really don't care if some says they do it without problems, I will never do that. Same as my rear diff, manual says it is "lifetime" fluid. Agian NEVER, lol.
I stick to these intervals.
OCI 5-6k
Trans pan dump once a year.
Coolant flush every other year.
Rear diff every 50k or so.
Powersteering fluid once a year.

Some may say I overdue it but I don't care it gives me piece of mind.

 

[BMWTurboDzl]

I follow the recommendation of the transmission manufacturer not the manufacturer of the vehicle. Case in point is ZF and my BMW. BMW has a 100k change interval however it is based on ideal driving conditions (BMW knows this I believe because they are known to provide a 'good will' replacement of out of warranty transmissions which have < 100k miles).

ZF has a severe service maintenance interval (~60k miles) but you'd never know it unless you visited their site.

Also todays transmissions with their mechtronics actually compensate shift times as the fluid ages. The real issue it seems is how well the electronics age and not the fluid. (Per my discussion with ZF rep)

 

[pbm]

I would change the ATF in a new car at 25 or 30K and then every 30 to 50K depending if I used synthetic or regular ATF. I would do it even more frequently if I towed or had a known weak A/T (like my old 2001 Accord BAXA).
A/Ts need all the help they can get to fight heat and regular fluid changes, Lubegard Red and even a transmission cooler can only help, IMO.

 

[Jim Allen]

ATF OCIs should be based on these factors:

1) Use, which encompasses driving cycles, load and conditions. Basically the amount of time it's at a temp over 200F and how many "cycles" it undergoes (shifts). A city driven car will have many more cycles than a highway car but one that tows or hauls may suffer from increase oxidation due to prolonged high temps.

2) Whether or not it has improved filtration. One of the primary reasons for an oil change is contamination. The first change is the most important, since the trans will generate 75 percent of its lifetime total of contaminants in the first 5-10K miles (a combo of break-in and the built-in grunge from manufacturing).


IMO, without being able to look at trans temps, I would use the following as a guideline. This assumes a good quality fluid. If you are starting used, then simply eliminate the first part and pick up an OCI according to the other factors.

NEW VEHICLE, NO EXTERNAL FILTRATION ADDED:

5-10K- A full oil change, with pan drop and filter change

30K interval thereafter, in heavy use or lots of high cycle, in in-town short trips: full fluid change pan drop and internal filter change.

or- 60K interval thereafter in moderate use, with balance of city and highway driving: full fluid change pan drop and internal filter change.

or- 100K interval with mostly highway and no hard use: full fluid change pan drop and internal filter change


NEW VEHICLE, EXTERNAL FILTRATION ADDED IMMEDIATELY:

30K- A full oil change, with pan drop and filter change, with external filter change

30K interval thereafter, heavy use or lots of high cycle, in-town short trips: full fluid change but no pan drop or internal filter, to include external filter change.

100K interval thereafter in moderate use and balance of city and highway driving: full fluid change, pan drop and internal filter change, with an external filter change.

150K interval with mostly highway and no hard use: full fluid change, pan drop and internal filter change, with an external filter change.

 

[Capa]

Great info as usual, Jim!

 

[Capa]

Quick question Jim Allen: I noticed that you didn't mention a flush but rather a fluid drain with filter change. Is there a specific reason why? When I went to my Dodge dealership 2 years ago they did a fluid drain with a filter change. I called recently to check their prices and they were pushing the flush, which doesn't include a filter change. The vehicle is a 2006 Grand Caravan 3.8. I was thinking of alternating between a flush and then a drain/filter change every 30,000 miles. Or is it better to just stick to drain and filter changes very 30,000 miles?

 

[tommygunn]

The reason he recommends just that is because its what the vehicle manufacturer recommends.

Flushes aren't necessary unless you let your transmission fluid get heinously bad. Flushing just sells better. Plus if they don't change the filter whats the point.

Its a dealership, what do you expect?

 

[Jim Allen]

Capa & tommygunn: I say "full fluid change" because I don't like the term "flush." A "flush" could be on of those nasty backflush things that often does more harm than good. Better terminology is "fluid exhange." What I mean is a complete change of the old oil, however that is accomplished. Without a torque converter drain plug, that would probably be via the cooler lines, either with a machine or the way I and many others do it at home. I believe it's important to change that pan filter (and clean the magnet is so equipped) for what I think are obvious reasons, unless the trans has an external filter. Dropping the pan also allows you to do a more complete fluid change. After that first change and pan drop, it's not as vital (IMO)

Capa: I don't have a problem with your method. It's a lot better service that most transmissions get!

 

[fpracha]

Originally Posted By: MuzzleFlash40
My Mercury Grand Marquis's manual says to change it at 100k under normal conditions. NEVER, I really don't care if some says they do it without problems, I will never do that. Same as my rear diff, manual says it is "lifetime" fluid. Agian NEVER, lol.
I stick to these intervals.
OCI 5-6k
Trans pan dump once a year.
Coolant flush every other year.
Rear diff every 50k or so.
Powersteering fluid once a year.

Some may say I overdue it but I don't care it gives me piece of mind.

>Trans pan dump once a year.
Are you driving >60k miles in a year ?
If not, then even if one is driving only 15k miles in a year (for a low usage vehicle), Do You still follow the 1 year interval for the ATF ?

 

[fpracha]

Originally Posted By: Jim Allen
ATF OCIs should be based on these factors:

1) Use, which encompasses driving cycles, load and conditions. Basically the amount of time it's at a temp over 200F and how many "cycles" it undergoes (shifts). A city driven car will have many more cycles than a highway car but one that tows or hauls may suffer from increase oxidation due to prolonged high temps.

2) Whether or not it has improved filtration. One of the primary reasons for an oil change is contamination. The first change is the most important, since the trans will generate 75 percent of its lifetime total of contaminants in the first 5-10K miles (a combo of break-in and the built-in grunge from manufacturing).

Hi Jim, really thanks for the great detail & guidelines!
My remaining questions are, for a new car:
(a) does the 1st 10-15k miles also have a minimum & maximum time limits (like just for example, say minimum 1-year & maximum 5-years to complete the 1st 10-15k miles) ?
(b) after the 1st ATF oil change, again are there any time restrictions or shoudl the ATF oil changes be just based on the xxk miles as you have stated in the details ?
(c) does the transmission temperature exceed 200F more in in-town driving or more in highway driving ?

 

[Jim Allen]

Originally Posted By: fpracha

Hi Jim, really thanks for the great detail & guidelines!
My remaining questions are, for a new car:
(a) does the 1st 10-15k miles also have a minimum & maximum time limits (like just for example, say minimum 1-year & maximum 5-years to complete the 1st 10-15k miles) ?
(b) after the 1st ATF oil change, again are there any time restrictions or shoudl the ATF oil changes be just based on the xxk miles as you have stated in the details ?
(c) does the transmission temperature exceed 200F more in in-town driving or more in highway driving ?


a) No time limit. Oil can't tell time so, within reasonable periods, time is not an issue. Also, the first interval is 5-10K, not 10-15K. As I said, the first change is the most important because the trans generates 75% of it's lifetime of contaminants in that first interval and it needs to be dumped or filtered. I didn't pull that number from my heinie. It comes from a pair of engineers, Eleftherakis & Khalil, that started doing studies on trans contamination in the '80s and are doing it still. The short version is that after analyzing thousands of trans samples, they revealed a lot of information (including the stat above) on transmission fluid and as a direct result, the OEMs have improved drastically their assembly processes and filtration.

b) Again, no time restrictions within reason.

c) That depends on the car/truck. Every vehicle has different operating temps and I only know a very narrow range of vehicles. In general, without a heavy load, cruising down the highway with the torque converter locked, temps are low... usually well below 200F (150-160 is "ideal."). In town, with the converter unlocked and the trans shifting often, they are higher but it takes a while to get them up from a cold start, so if you commute is under 10 miles, you may not be seeing 200F for very long. It's time at temperature that counts. ... hours and hours at 200F, not a slow buildup then five minutes or so at a higher temp. Also, 200F isn't a dreadedly high number but it's the point at which oxidation has increased significantly, so preferably, you keep fluid temps below that or be faced with more frequent oil changes. Again, better fluid resists oxidation better, so there is a wide range of OCIs based on the actual oil. Those ATF life charts you see are based on oxidation rates at the various temps.

 

[fpracha]

Originally Posted By: Jim Allen
Originally Posted By: fpracha
(c) does the transmission temperature exceed 200F more in in-town driving or more in highway driving ?
c)... It's time at temperature that counts.
... Again, better fluid resists oxidation better, so there is a wide range of OCIs based on the actual oil. Those ATF life charts you see are based on oxidation rates at the various temps.
but regardless of the actual oil, the 1st change of ATF is to be at 5-10k miles, correct ?

 

[Jim Allen]

Originally Posted By: fpracha
but regardless of the actual oil, the 1st change of ATF is to be at 5-10k miles, correct ?


In my opinion, yes. I spoke with Abe Khalil, one of the two engineers I mentioned and he told me the first thing he does with a new car is drive it home and change the transmission oil. When I pressed him a little on the somewhat pedantic sound of that, he said that 5K is OK but no more than 10. Basically as early as possible.

Caveat: Some of the info I got from him, and other sources, later indicate that the OEM have really cleaned up their act and import carmakers were always a bit better at clean assembly than the Americans. This might indicate that today there is a bit of fudge factor.

 

[KrisZ]

I did the first ATF exchange at about 15k, and then at 60k. I think I did two drain and fills in between. I still have the original ATF filter and I don't think I will be changing it any time soon.

 

[Ken2]

Quote:
Well, as for the 'vette, I have the original owner's manual in front of me. "sealed lifetime maintenance free". Is that a lie?

Absolutely true. The fluid is good for the life of the transmission. The funny thing is that if the fluid is changed periodically, the transmission seems to live longer....

As stated above, the additives in the fluid do deteriorate with service, and the oil can oxidize. Even GM was saying with the introduction of their recent Dexron-VI that it was their first ATF good for 100,000 miles.

 

[Donald]

While the new synthetic ATFs may last longer under the best conditions, the contaminants are floating around your transmission for that long. So one either needs to install an inline filter like the Magnefine or swap some fluid out (that still might be OK) in an effort to get rid of contaminants.