Auto box filling accuracy

[james2747]

I have the W211 E270 Cdi.
I have just changed the transmission oil and filter.
As there was no dipstick (which is so annoying) I re-filled with exact same quantity that came out but as the new filter will soak up some ATF fluid I decided to add another pint (note I'm over 60 yrs old so imperial units for me).
Lots of articles say you must fill to the exact level ... WHY?
I can understand that too little oil could well cause oil to be 'overworked' and perhaps get too hot and degrade quickly ... but if I overfilled the level by say a full litre (or 1.75975 pints in my world) I can't see that being a problem. There are no moving parts like a crankshaft thrashing about in the 'excess' oil.
Does anyone know why there appears to be such an emphasis on the level of ATF being 'spot on'.
If it's so critical to get it correct, why 'O' why did MB not provide a means of checking the level.

 

[steveq]

The ATF provides more than lubrication. The auto box operation uses the ATF for gear changes and the torque converter uses the ATF as a critical part of its function. The level of fluid is therefore important.
Assuming you have a 722.6 gearbox (5 speed), you can purchase a dipstick to check the fluid level. The fluid level is checked with it up to full working temperature and with the engine running.

 

[thebiglad]

The problem with the MB autobox set-up and oil level checking is this :

Yes you can empty/measure and refill with the same quantity; or check with an aftermarket dipstick before emptying and after refilling BUT how do you know if the level was correct before emptying ??

 

[grober]

https://www.quora.com/What-are-some-symptoms-of-too-much-transmission-fluid

Too much fluid may put pressure on seals , in particular any seals involved with electrical connections to the box conductor plate. While there are no reciprocating parts in the box there are plenty rotating parts which can cause overfilled fluid foaming with all the problems that can generate. Its particularly important that gearbox levels are measured at specific temperatures and possibly with the engine running as per manufacturers recommendations.

 

[james2747]

The ATF provides more than lubrication. The auto box operation uses the ATF for gear changes and the torque converter uses the ATF as a critical part of its function. The level of fluid is therefore important.
Assuming you have a 722.6 gearbox (5 speed), you can purchase a dipstick to check the fluid level. The fluid level is checked with it up to full working temperature and with the engine running.

hi Steveq
Thanks for the reply … I did purchase a dip stick …. actually 2 dipsticks, as first one from ebay was no use at all. Even second one …. which cost me £15, wasn't any use as it didn't seem to have a positive 'stop', so you could push it in too far and therefore no accurate measure of oil level was possible.
I assume I'll need to buy a genuine MB dip stick … which will probably need a second mortgage to purchase!

 

[Trickythemerc]

I have the sealey dipstick and it works just fine. Cost me about £18.00 if memory serves.

 

[whitenemesis]

As long as it has the little diamond stop, should be fine. Many available from Amazon. As above Sealey do a reasonably priced example

 

[markmifsud]

I think part of the problem with overfilling is that there will be an element of frothing(mixing air and oil). As air is very compressible and oil is not, the valves/lockup clutch etc could end up disengaging without warning.