Tranny overfill - just a little.

So, I changed the fluid in both diffs, transfer case, motor oil and flushed the tranny, replaced the filter and adjusted the bands.
I was doing that ever-so-scientific method of topping off the tranny
(neutral, hot on a level surface) . The level was just below the hash marks. Based on how slowly it was going trying to get the right amount in, I made the judgement that I need exactly half a quart to hit it right in the middle of the hash marks.
Goddamnit, I put in half a quart and now the level is about an 1/8" above the hash marks on the "M" of the word "Max".
Do I need to drain some off, or is there a little fudge room?
2004 Ram 2500, CRD, 48RE.
Thanks, Craig C.
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You'll be fine.
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On May 20, 10:23 pm, "Tom Lawrence"

Thanks. I figured there was some room for error.
Question: why is the top off when the truck/tranny is hot? Why can't the engineers come up with a method of measuring the proper amount of fluid when cold?
Craig C.
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wrote:

Perhaps folks add cold fluid to hot. Few people totally change all their fluid. I don't know just guessing.
Roy

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Because of the amount of expansion ATF undergoes as it changes temperature, it's hard to be completely accurate. Yes, they could easily mark the dipstick for a cold check, but since the fluid has to be checked with the engine running and in neutral (to make sure fluid is circulating throughout the transmission, since fluid isn't pumped in Park), the temperature of the fluid could vary greatly depending on how it's checked (remember that the fluid will be heated by the radiator's 'cooler', if the engine coolant is above ambient temps).
To illustrate just how much ATF expands, consider that the proper level on the dipstick for a 'cold' vehicle is about halfway between the end of the dipstick and the 'M' in 'MIN', whereas the same fluid level at full operating temperature (195F) is at the top of the 'OK' range.
The issue here is, if you fill the tranny completely full while cold (up to 'MAX'), when it heats up, it will expand enough to where it could come into contact with the rotating assembly, and foam up. The pump then sucks in the foamy fluid, you get pump cavitation, loss of hydraulic pressure, and just general badness.
You want enough fluid in the pan so that the pickup screen is always immersed in fluid, even during hard cornering (or as hard as a 7,000+ truck can corner :) If you consider that the pickup is pretty low in the pan, and the dipstick barely extended below the level of the valve body, you can see that you have a good deal of 'fudge factor' when it comes to the fluid level.
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On Mon, 21 May 2007 16:22:35 GMT, "Tom Lawrence"

Not really, it is quite predictable. The problem would be what is considered cold (70 degrees or zero) and this would effect reading. I have seen some trannies that have hot and cold full marks on sticks. If you overfill by 1 pint on a tranny that hold 8 quarts or more in total capacity, you are not going to break the bank and it is no cause for concern. If they were as sensitive to fluid level overfill that some seem to think they are, there would be a lot more tranny problems out there. When I used to do hard core off roads long ago (before it was even the craze it is today) I used to overfill my engine and tranies a bit to maintain better chance of fluid flow through pump at extreme angles of operation. Never had any problems from it. I also have a 50 year old JD utility tractor that I use to bush hog some pretty nasty side hills and slopes with extra counter weights on uphill side (170 lbs a piece) and I overfill it by 1 quart so that it always maintains engine oil pressure. Been doing that for almost 20 years now and it has not leaked or failed yet. Generally with a engine you have to get in the 25 to 50% overfill range before you can maybe start to have problems. ----------------- TheSnoMan.com
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Tom Lawrence wrote:

Okay, makes sense. I knew that there was a fudge factor on the low side. In fact, much to my surprise, when I started this project yesterday, my tranny was 1 quart low. I guess last time I did this I didn't get the level correct. But I didn't have any trouble in 25000 miles. I was just a bit freaked out because it says "DO NOT OVERFILL" on the dipstick.
Thanks, Craig C.
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