High Mileage ATF - how does it work?

[adreed24]

I recently read some information about "High Mileage ATF", particularly Dexron II / III type. Most of the major engine oil companies, like Valvoline, Castrol, Pennzoil, etc., make it.

I know that "high mileage ATF" has seal conditioners to help stop small leaks, but I also read that these fluids are somewhat thicker than regular ATF.

This "thickness" is supposed to help the gears grab each other better to reduce slippage. Also, this "thickness" is supposed to act as a "cushion" between parts to compensate for mechanical wear in an older transmission.

I'd like to know if this information about "high mileage ATF" is accurate.

Any ideas anyone?
Thanks in advance!

 

[Mickey_M]

quote:

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adreed24:
.... I know that "high mileage ATF" has seal conditioners to help stop small leaks, but I also read that these fluids are somewhat thicker than regular ATF.

This "thickness" is supposed to help the gears grab each other better to reduce slippage. Also, this "thickness" is supposed to act as a "cushion" between parts to compensate for mechanical wear in an older transmission.

I'd like to know if this information about "high mileage ATF" is accurate. ....

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The current crop of ATFs involve high-quality base stocks, generally PAOs and Group III mineral oils, generously fortified with antioxidants and friction modifiers. Some of the friction modifiers (e.g., esters) are also antioxidants.

The higher quality base stocks extend the life of the fluid, just as synthetic motor oils allow you to extend oil changes.

The antioxidants extend that life even further, protecting the base stocks from heat and degradation.

Since the fluids are semi-synthetic, they are thinner when cold and thicker when hot, which means less wear on the transmission and better shifting.

The friction modifiers, additives, and base stocks reduce wear but they also provide different engagement characterstics than previous ATFs - you get less "slam" and more gradual engagements.


.

 

[Russell]

How does Mobil 1 Dexron III synthetic atf fit in this picture?

I used in about 5,000 miles ago on my E34 95 BMW 525i. Seems to work fine. BTW, other BMW users seem to think that Mobil 1 ATF performs better in the GM transmissions used in these cars than "regular" atf in terms of longer life and shift quality.

 

[MolaKule]

quote:

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I know that "high mileage ATF" has seal conditioners to help stop small leaks, but I also read that these fluids are somewhat thicker than regular ATF.

This "thickness" is supposed to help the gears grab each other better to reduce slippage. Also, this "thickness" is supposed to act as a "cushion" between parts to compensate for mechanical wear in an older transmission.

I'd like to know if this information about "high mileage ATF" is accurate.

---

Your information is only partly correct. The HM ATF fluids do contain extra seal swell agents for tired seals that may be leaking.

The high mileage ATF fluids are a bit thicker at around 8.5 cSt verses the regular 7.5 cSt but only because they shear.

The viscosity has little to do with slippage or engagement, since the specialized friction modifier additives control slip and engagement.

In my view, you only need thicker fluids (9.0 cSt to 10 cSt) for racing in order to transfer a bit more HP in the torque converter. Otherwise, the thinner fluids at 7.0 to 7.5 cSt are best for daily drivers.

In the future, thinner ATF fluids will be the norm since they will increase slightly the mpg.

Please see these threads about more info on ATF:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=4;t=000315#000000

 

[adreed24]

Thanks for all the information. The reason I am interested in "high mileage ATF" is because I have a 1987 Jeep Cherokee with 220,000 miles on it. It has the original automatic transmission and it has developed a bit of slippage...I think.

When I start off and climb up a steep hill, the transmission will make a short, grinding sound, and there will be a quick pause in my forward motion, until things seem to "grab" and the Jeep moves forward, with no other problems.

Also, when I start off (on a level street) and press the gas too hard, the same noise and pause occurs, then everything is fine. There are no other problems while I am driving; the shifting seems to be smooth as always.

Is what I am experiencing...slippage? I don't know, because we have never had a car this long with this much mileage.

I don't have the transmission "power flushed" because I was told that it can loosen debris in an old transmission, causing more problems. I just drain the pan and replace the drained fluid with fresh. I was told this is best for my situation.

I have been using conventional Pennzoil Dexron II, then III, ATF in the transmission and transfer case, and conventional Pennzoil differential fluid in both differentials, since it was new.

I don't know what to do about the slippage problem. I know I should get it looked at, but when I do, the transmission will still have high mileage on it.

I spoke to a Pennzoil rep. and he told me to stay with the conventional ATF fluid, until the problem gets worse, then switch to "high mileage ATF".

I'm sorry this post is so long, but I figured I better include as much information as I could.

Does anyone have any opinions on whether I should try "high mileage ATF"; maybe try some type of additive like "Lucas ATF Stop Slip"; or should I just keep doing what I have been, regarding fluid type and changes?

Thanks in advance!

 

[Big Jim]

I don't think there is any fluid that will resolve your problem at this point. It won't hurt to try changing the fluid, but don't hold your breath. I think you are hoping to find a mechanic in a can.

 

[unDummy]

The best thing for you to do is drop/clean the ATF pan, replace the ATF filter, and refill with high mileage ATF.

If that doesn't help, safe your money for a rebuild. 220k miles is a good life for ANY transmission(especially the poorly maintained ones).