Allison Transmission Fluid Capacity

[tennsmith]

I have a MD3000MH transmission in my Horizon and drained it via drain plug and removed the filters to replace them.  I caught all the old fluid and it looked like a lot, so i measured it to see how much and it was damned close to 19 quarts, the listed "capacity" of this transmission.  HOWEVER, when I read the Owner's manual and other tech information on the internet, they all say that only about 10.5 quarts will drain during a filter change and that the rest of it is trapped in the valve body and torque converter.  So I'm asking...is the 10.5 qt the correct value for the shallow (2") pan?  All I can figure is that the PO filled it to capacity, not knowing any different.

The transmission has been working OK, AFAIK, but I have no reference as to proper/improper operation as this is my first experience with an Allison transmission in a big truck chassis.  The fluid was pure with no contaminants and smelled like transmission fluid with no burned smell.

I am tempted to replace only 10.5-11 quarts and see what the onboard fluid level measuring system indicates, but the transmission has to be up to operating temperature to make this measurement and if 11 qts is NOT enough, then I fear I may damage the transmission if I run it too low on fluid warming it up.  Hindsight being 20/20, I should have checked it via the onboard system BEFORE draining, but I did not.  Any advice as to how to proceed?

 

[Ned]

Is that on a Freightliner chassis?  If so, call them (1-800-FTL-HELP) with your VIN number and they can tell you what the capacity of your transmission is and how much fluid you should add on a filter change.

 

[Gary RV_Wizard]

Maybe the drain plug you removed was on the torque converter?

You should have a real dipstick as well as the electronic level check. See if any oil shows on the dipstick after putting in 10.5 qt.

Allison has a Tech Assistance hotline too. See
http://www.allisontransmission.com/service/faq/index.jsp?CategoryID=6

 

[tennsmith]

Thanks Ned and Gary, those are good ideas.  Gary I do have a transmission dipstick and hadn't thought about using that.  The drain plug I removed was not on the torque converter and was located in the transmission cast aluminum pan.  Most of the Allison literature indicates the onboard system is far more accurate than the dipstick, but the dipstick would give an "estimate" of fluid content.  I'll try that and give Freightliner a call also.

 

[Terry A. Brewer]

Bob

>>Any advice as to how to proceed?<<

The Allison shops put transmission in gear with foot on brake & rev engine....transmission heats up in a few seconds.

 

[tennsmith]

Well, the excitement is not over yet.  Replaced the filters, replaced 10 qts of fluid and it appeared that there was fluid on the dipstick so I decided to take her out for a test drive.  Drove about 8 miles to a nearby Lowes where there was a nice level parking lot and pulled up and went into the electronic oil level check mode and the indicator, after a period of "settling" time, said that I was 4 quarts low.  I figured that it would be "easy" for me to be 1-2 quarts low, so I emptied the remainder (2 qts) of a partial gallon into the transmission which now makes 12 quarts total, expecting the sensor now to indicate 2 quarts low.  I tried it in the parking lot before I left, but adding the 2 qt of "cold" oil to the transmission cooled the fluid below the point where the auto level check will work, so I decided to drive back home which involves about a 3 mile uphill grade, knowing that would heat it up to the proper temp.

After arriving home, I checked it again and it still shows 4 quarts low!  So my question, at the moment, is....is 4 quarts the maximum "low" quantity that the transmission check will register?  Based on what I drained out, I'm still 6 quarts below what I drained.  Or, is there something kaput with my oil level sensor?  Headed out now to see if I have an auxillary transmission cooler, as the oil in that plus the to/from lines is not included in the Allison 10.5 qt "refill" numbers.

Allisonman?....are you out there?

 

[Gary RV_Wizard]

I think I would replace what I took out and be done with it.

Maybe the 10.5 qt number applied ONLY to a filter change. You drained fluid as well and that is not necessary as part of just a filter change alone.

 

[BernieD1]

Bob

The electronic dipstick maxes out at 4 qts. You should use the dipstick, there is a cold setting, to make sure you don't have too little oil and, when that shows the level to at least the bottom of the add mark, then you can try driving to warm up the oil.

 

[tennsmith]

Gary, you hit the nail on the head and it is good information for others who might attempt servicing their own transmission.  I received a reply to a personal message I sent to Allisonman and he responded that the two filter cavities are isolated from the main sump and if you only replace the filters without draining the sump, the 10.5 quart value is close to being correct.    However, if you drain the sump, additional fluid is required approaching 19 or so quarts, so the situation has been demystified.  The Allison Owner's manual is not really clear on this point.  Thanks to all and thank you BernieD for the 4 quart limit information, that almost had to be the answer, based on what I was seeing.

 

[Gary RV_Wizard]

Glad that one is solved. Now if only I could figure out why I drain 5.5 gallons of oil from my ISL engine, but have to put almost 7 gals back in to read "full". The filter holds about 1.2 quarts, so where did the rest go? Is the dipstick wrong and the engine simply throws it out or burns it? But if so, why does the dipstick continue to show full after driving many, many miles?  I've decided this is one of life's mysteries that I will never come to know, so as long as the engine is happy I buy the 7 gals of 15W40 and a new filter every year and pour myself an adult libation to celebrate when I'm done.