Assuming I have measured the tranny level when hot and with engine running correctly. The level is at max mark. If I measure the level again when engine is cold and make a MARK on the dip stick ( it would be higher), can I use it as reference from now on to top up when cold? Any flaw in the concept?

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

One variable is “cold ATF” temperature. What is the variation in fluid level after a 60*F cold start vs a 30*F cold start? FWIW I’ve known GMs and Toyotas with cold ranges in the dipstick and no discussion in the owner manual as to what cold is.

Sixto
98 E320s sedan and wagon

I don't need to be precise as measuring it the 'right' way when hot is a pain. There is no perfect level so to speak. The tranny doesn't care if it is a tad over or under. Would this be a good enough method for a daily driver, not talking about space shuttle?

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Try driving up a steep hill with the fluid level "a tad" low and you will change your mind about that.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

The only flaw I can think of is if this worked why wouldn't all the
manufacturers recommend it? There must be a reason.

Maybe as an experiment you could check yours cold every day for a month or so and see if there is any variation day to day

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Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K

I would have problem if the level is a tad off the max mark??

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

The new, cold mark would be higher than the hot mark if: 1) converter drain-back volume exceeds the reduction in volume due to lower fluid temperature, and 2) cold checking is performed before engine start.

A potential flaw in the process would be introduced if converter drain-back volume is not consistent. A check of level shortly after a cold start would eliminate the drain-back question.

On the GM and Toyota samples mentioned, cold is cold running. I’m not aware of any relevant fluid measurement with the engine not running.

Sixto
98 E320s sedan and wagon

Because the fluid expands in proportion to temperature, you should measure it at a consistent temperature. If everything is at normal operating temp, then the temperature is regulated to a narrow range (the transmission 'cooler' is more accurately thought of as a 'regulator' which matches transmission temperature to coolant temperature). OTH, "cold" can be anything from ambient temperature to 185F, and the level would depend on the temperature of the fluid at any point in time.

The engine has to be running, because fluid becomes engaged in the valve body, clutches and converter while running, then some of that falls back into the pan when the the pumps stop and aren't maintaining pressure. So you can't judge running level when the engine is stopped.

To take the mystery out of it, they're just looking for a level that's a bit above the filter intake under all normal running conditions. If the level falls below the intake, pressure falls and the clutches try to disengage, then reengage as fluid falls back into the pan. Eventually the transmission will overheat. So the primary consideration is that there's always a supply available to the pump.

^Don't forget about that transmission cooler too.

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