Service trans, no TC drain plug
 

Happy Easter everyone.
Does anyone know of a way to do a complete transmission service when the torque converter does not have a drain plug. The transmission was rebuilt about a year ago and the torque converter was replaced, but no drain plug.
I want to change it over to synthetic ATF so I need to get as much out as possible.

Thanks in advance.

PaulM

At our shop we have a transmission flush machine. Its the best option on cars without a torque converter drain.

No drain plug? Blinking heck that's gonna mess up your plans...

...what a pain. I have to ask the obvious => are you sure there isn't a plug?

Not a pain, What year car and model?

You can do a fluid exchange.

Martin

what car...

Sorry, this is my 84 500SEL 722.3XX

PaulM

Stretch, a couple of weeks ago I was doing valve guide seals and saw the mark I had put on the front pulley marking where to set the engine so the plug would be at the right place for servicing the trans. I checked and of course the plug wasn't there. So before I put the rockers and plugs back in I looked for the plug by bumping the engine over with a remote start button. I could have missed it but that is the way I found it before. Keep in mind, I was outside on a gravel driveway and had NO helper.
When I do the service I will look for the plug again. If I can't find it I want to be prepared to do it another way if possible.
Is it possible to add a drain plug without removing the trans?
Thanks again for any help.

PaulM

The pulley mark you made prior to having the transmission reworked would no longer work as the converter is now phased at some different teeth engaging on the input shaft meaning even if you removed the converter and then did the rotate slightly and wait for 3 bumps to seat technique - the converter will not be in phase with the engine anymore.

Bumping with the starter will spin it too fast and you may not be able to catch the drain, you will need to spin the engine very slowly to see the drain.

For some reason if you dont find it then you can do a cooler line flush, The cooler line is the exhaust port of the torque converter, use the transmissions own pump to do the job for you. I do that on nearly all cars with a painful drain procedure

infact my own E320 does not have it and the only way for a full ATF change is the cooler line drain out.

If possible remove the spark plugs and then turn the crank by hand to check - if the drain is there it will save a whole lot of trouble.

I was thinking about drilling and tapping a hole in the converter as a possible solution if indeed it did not have drain plug. I guess that could work. Minimal swarf would end up inside the converter during the first drilling operation as loads of fluid will piss out... tapping the hole might leave some swarf on the inside though. There is a potential out of balance problem in fitting a new drain plug though - keep this to a minimum by fitting a small short bolt and a thin washer.

Zulfiqar, could you elaborate on using the cooler lines to drain the converter. I think I understand that you disconnect the line from the transmission at the radiator, start the engine, and the fluid will be pumped out of the converter. If this is correct, do you do this with the pan and filter removed? Do you do this while going through the gears or in park?
I have been working on cars most of my life (now 72) but have never done this procedure so any hints will help.

Thanks again to all.

PaulM

This is how I do the fluid Exchange method for the W210 and W140 which out of the 722.6 transmission the exit line is on the driver side, and the return on the passenger side.

On the older tranny's they both come out of one side..

The process is the same?

See post 11 for the W210

Will Vin# reveal Torque Converter Drain Plug - Mercedes-Benz Forum

See Post 6 For W140

What is my transmission? Fluid? - Mercedes-Benz Forum

For others with a first generation 722.6's (All mid to late 90's cars). I'd suggest you do not do this as you can wipe-clean the K2 bushing bearing clean of lubricant, and you may get K2 bearing failure. Second Generation 722.6's are okay(+2000)

Hope it helps,

Martin

the way I do it on my 2000 E320 (drain on transmission pan but no drain on torque converter) is

empty the pan from the drain plug - remove pan and install new filter, install back.

fill new ATF in whatever quantity you drained out from the pan.

undo the return line at the radiator cooler and put it in a bucket or jug marked in qts (slip some hose on it to guide it)

start engine and let it pump out 2 qts - shut off engine, fill 2 qts fresh ATF in transmission, start engine, drain 2 qts, stop engine, fill 2 qts fresh ATF and you will be done. You will see fresh ATF at the cooler line.

Couple the cooler line back to the radiator.


Whilst servicing GM, Ford, etc with no drain bolt on pan I undo the return line at the transmission or the radiator and start the engine to drain about a gallon or abt 5 qts of ATF and shut off the engine.

now when the pan is removed I only get a small amount of ATF to handle in the pan whilst under the car, I do my filter change or work, button it back up fill it up with fresh ATF, do the cooler drain once again till I see fresh ATF being pumped out. For vertical split cases and no sump (Honda etc) I dont even bother to undo the drain - I do the cooler line drain and refill


however I still advise to check the torque converter for the drain, you will need to rotate the engine very very slowly to see the bolt, bumping the starter spins the engine very quickly for finding the bolt through the little 1 inch window in the transmission bellhousing.

the person has an old 722.3xx transmission and he cannot locate the drain plug on the converter.

but - good advice for the early 722.6

Yea, the process is similar for ANY transmission on any make or model. Torque converter drain plug or not?

except some..

e.g. toyotas new CVT which is in the Scion iQ. The cooling circuit for that transmission is that coolant goes into the transmission heat exchanger which is inside the transmission rather than the ATF being pumped to the ATF cooler which should be in the radiator

and then is the level check, no dipstick, no hole to feel or dribble, to do that the drain bolt has a funnel inside to determine level but that can only be determined correctly when the fluid is between 30-41 degrees celcius precisely.


sorry about the rant....

had the misfortune of working on one recently.