As a fulltime RVer, I came up with the following method for changing my ATF at RV parks. After every 3K engine oil change, I use two empty 1 gal oil jugs to sneak under truck and drain ATF from pan. After a full service 18 qt change and new pan filter 45K ago, all I've done since then is to R&R the 6 qts from the pan.

After doing an analysis to estimate the "freshness" of my ATF changing it this way versus a full 18 qt every 30K, I've tentatively decided to stick with my approach indefinitely unless I hear reasons why I shouldn't.

I attached a pic of my spreadsheet analysis, where I used the metric (qt-mi) in a manner analogous to (man-hrs) for estimating how hard the ATF has been worked at each 3K increment as mileage increases. At each 3K, 1/3 of the ATF is replaced so that 2/3 of the old mix remains. If read along a diagonal, the #'s in the matrix give the # qts remaining in the mix at each successive change. As an example, for the change I just finished (#15 @45K) there was only 0.06 qts of the original 18 qts still in the mix.

The column on far right is the "freshness index" for a complete 18 qt change every 30K and the column to the left of that is for 6 qts every 3K. As you can see, the 6-qt strategy approaches a constant ~162 qt-mi whereas the 30K approach varies linearly from 54 to 540 qt-mi.

I appears to me, that continuing my 6-qt every 3K method indefinitely provides a constant freshness that is better than the average one provided by the 18-qt every 30K standard. Of course, instead of using just 18 qts every 30K, my method uses 42 more qts, but at Wal-Mart prices this is only about 85$ which is much less than I paid at Ford for my last full ATF service.

 

That will definitely keep it fresh, have you looked at it only doing it every other OCI should still keep you ahead of the game and save a little $$

 

Your wish is my command! With my bad back and watching golf, I don't have anything better to do anyway. I went back and ran the analysis for your suggestion of starting with 18 qts fresh, and then R&R 6 qts every 6K. I posted pic if you're interested in details.

The asymptote is now double (324) the previous (162), as one might of guessed, and is now higher than the average (270) for the standard 30K method. Also, there's a much larger difference in the amount of old ATF remaining in the mix. For example at 30K, there's only 0.47 qts of original ATF using 3K changes, but 3.56 using 6K changes. In any case, I've got to get under truck after having oil changed to check things out.

 

You lost me a little, but it looks good. I think Kwik once said the drained the pan every other change on his last truck Auto w/460 and never had a problem.

 

Yes I did and it was for an E4OD. It always smelled nice and sweet coming out. Never a burned smell. But it only had to pull a 4500 lb trailer. That truck only pulled my Cedar Creek for one trip and it was sold. Any hill was a nightmare going up or coming down with that one.

 

Since you did offer in another thread, I'd be interested to see your attachments. Have you figured how many miles it would take to actually get all (well at least most) the original fluid out of the truck by following this method? Changing 33% of the oil each time would mean you're also draining 33% of the new oil each time also.

 

The chart below is for starting out with a full 18 qt fill and then replacing 6 qts every 3K miles. The yellow cells give the # of qts of the initial 18 qt fill that remain versus miles. As you can see at change #8 which is 24K miles there's only 1 qt of the original fluid remaining.

The 3 columns on the far right side give the qt-mile comparison between replacing 6 qts every 3K miles versus replacing the full 18 qt fill every 30K miles. For example at change #3 you've got 3K on 6 qts, 6K on 4 qts, and 9K on 8 qts for a total of 114 qt-mi versus 9K on 18 qts for 162 qt-mi.



The chart below is for starting out with a full 18 qt fill and then replacing 6 qts every 6K miles. The yellow cells give the # of qts of the initial 18 qt fill that remain versus miles.

The 3 columns on the far right side give the qt-mile comparison between replacing 6 qts every 6K miles versus replacing the full 18 qt fill every 30K miles.

 

Thanks for posting this again. The downside I see to this method is simply the cost. Wouldn't it have been cheaper to just pay someone to change the fluid every 30k than buy 6 qts every 3,000 miles?

 

I never let anyone work on my truck when it's out of my sight! As a fulltime RVer I can't drain all 18 qts at an RV park without attracting too much attention! At 30K (2001) a very nice Ford dealer gave me a new TC because of the TSB for spring rattle on my early 99, I got all new fluid then, and even got to watch. From then on I'd pull into a Jiffy lube to change oil and have 6 qts drained then. Then they striped my tranny drain plug and I needed a new pan. From then on I just snuck under my truck at dusk in the RV park and did both oil and tranny at the same time. As I recall 6 qts of ATF at Wal-Mart was less than $12 and the average ATF freshness my way is much better than changing 18 qts every 30K!

As you can read here...

Freightliner Recall Notice!
Freightliner Recall Notice! - TheDieselGarage.com

...I was required to have this work done out of my sight and of course that lead to my concern regarding the correct adjustment of the axle stop bolt!

 

Thats pretty close to what I do except I drain the pan every other oil change. Then top it back off with good ol Mercon ATF. I drop the pan and change the filter every ~25k. But I also have an inline Magnefine filter that I change at ~15k intervals. My fluid is always pink and smells normal.

 

Since you're under the rig with two gallon jugs, what would the math look like if you drained all EIGHT quarts each time (instead of just six), and did it every-other-lube-oil change?

Pop

 

I've been told by several "experts?" that you only need to drop the pan every 100K to change that filter! I used to change my Magnefine every third 3K oil change and both fuel filters as well.

I also installed a Magnefine in the power steering system and at every 3K oil change I'd suck as much as I could out of the power steering reservoir with a hand pump. Every 3 years I used a hand pump to empty the master cylinder and then kept topping it off as I had someone help me bleed the brakes.

 

On my early 99 6 qts is all that would drain from the pan. The other 12 qts stays in the TC, and trying to drain the TC is a messy PIA! Besides once I was under the truck anyway I'd first drain the tranny until the first tranny jug was nearly full then stick the 2nd jug under the tranny and concentrate on not spilling any engine oil and I didn't have to worry about over flowing the second tranny jug.

 

What up Eugene! Glad to see you still lurk about!

 

And here all this time I thought you were talking about applying this method to the Freightliner.

Guess I should have noticed the date of Post #1 above. I did look, but it was at Post #7.

Details, details.........

Pop