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View Full Version : Checking Transmission Fluid Level After Full Service ==> Why?


ducsingle
03-09-2009, 03:54 AM
I've surfed through numerous posts on the issues surrounding accurately checking the transmission fluid level.

My question is why is this even necessary after a full fluid drain and filter change? Shouldn't all of the transmissions be dimensionally the same (within reasonable tolerances) such that after a full service, you add X liters of fluid and button it up?

autostaretx
03-09-2009, 04:57 AM
For starters, how does the random transmission-filling mechanic do it?

Does he have a central pumping system (think gas pump) and metered nozzle?
Does he open quart/liter cans/bottles and -guess- that final fractional bit?
Does he do an -accurate- conversion from quarts to liters (or back) before filling it?
(in the US, oil comes in quarts, in Canada the same bottle holds a liter).

How "drained" did he do? Did he turn the propellor shaft to get those last bits out?
Were all drain and air vents opened? (did he bother to clean the magnetic grit-catcher, if it exists?)
Is your tranny the 3.72, 4.11, 5.something gear ratio? Did he correct for the differing volume of the gears?

Personally, i'd trust the wet dipstick in the engine...

Yes, "mass production" -should- create a repeatable situation where draining (or suctioning) then filling with the -known- amount should do the job. (i happily pour 9.5 quarts of oil into my 2005 Sprinter -before- checking).
But it does not hurt to double-check with the dipstick, and it certainly -can- hurt not to.

--dick

rlent
03-09-2009, 05:15 AM
Is your tranny the 3.72, 4.11, 5.something gear ratio? Did he correct for the differing volume of the gears?
Dick, the above ratio numbers refer to the rear-end (differential) and should not have anything to do with the transmission - the transmission should be the same regardless of what rear-end gearing is being used (assuming same tranny model used - which in the Sprinter it apparently always is - at least so far)

rlent
03-09-2009, 05:17 AM
My question is why is this even necessary after a full fluid drain and filter change? Shouldn't all of the transmissions be dimensionally the same (within reasonable tolerances) such that after a full service, you add X liters of fluid and button it up?
What if your transmission has an auxiliary cooler fitted into the system ?

Direct observation is always far superior to an assumption.

ducsingle
03-09-2009, 05:34 AM
Ah, good point on the transmission oil cooler. That could vary oil volume quite a bit depending on line length, cooler volume, etc. And different draining techniques could result in some variation of residual fluid in the transmission. As far as measuring what goes in, I would think a mechanic could count the number of empty bottles on the workbench and do a little math!

Surfing through various posts, it sounds like some folks have difficulties using the factory dipstick tool, resulting in inconsistent measurement results?

Then there were numerous posts about the need to measure the temperature of the transmission fluid as indicated by a voltage output accessible by removing the driver's seat. How many folks are actually doing this? Or do most folks just go for a drive under reasonable load and check?

All of this sounds like a total PITA for what should be a simple service routine - - - definitely not something I would trust an average diesel tech to do. Is the transmission really that sensitive to the fluid volume?

autostaretx
03-09-2009, 05:48 AM
...the above ratio numbers refer to the rear-end (differential) and should not have anything to do with the transmission -

...sigh.. too many years as an old air-cooled VW mechanic and front-wheel drive systems...
their trannys and diffs all shared the same oil

Another reason to use the dipstick...

--dick

rlent
03-09-2009, 05:56 AM
Ah, good point on the transmission oil cooler. That could vary oil volume quite a bit depending on line length, cooler volume, etc. And different draining techniques could result in some variation of residual fluid in the transmission.
The disclaimer notation for the transmission fill capacities from the '06 service manual in the Lubrication section:

"Dry fill capacity. Depending on type and size of internal cooler, length and inside diameter of cooler lines,
or use of an auxiliary cooler, these figures may vary. (Refer to appropriate 21 - TRANSMISSION/AUTOMATIC/FLUID - STANDARD PROCEDURE)."

Surfing through various posts, it sounds like some folks have difficulties using the factory dipstick tool, resulting in inconsistent measurement results?
Ones gets the hang of it after doing it a few times - I drive alot of miles (relatively speaking) - I may check it as much as several times per week.

Then there were numerous posts about the need to measure the temperature of the transmission fluid as indicated by a voltage output accessible by removing the driver's seat. How many folks are actually doing this?
I do not (at least electronically) - I do have a gauge that measures the temp from the output line from the transmission to the cooler. The temperature is rarely, if ever, exactly at either of the two temps marked on the dipstick - I try to err a bit on the high side, rather than low.

All of this sounds like a total PITA for what should be a simple service routine - - - definitely not something I would trust an average diesel tech to do.
It's not that big of a deal - providing you are familiar with doing it. If it's something you do rarely, well ......

Is the transmission really that sensitive to the fluid volume?
My guess on slightly overfilled - probably not so much. Grossly overfilled would be another matter (because the gears will foam the fluid, which will cause overheating)

On the low side - probably the kiss of death, if run for any length of time significantly low. Low enough, and it will slip - you will know it.