I'm changing out my trans oil and I went to drain the torque converter, but can't seem to find the drain plug. Looking just in front of the transmission pan, I see a plastic plug in a hole in the housing. After removing it, I rotated the crankshaft hoping to see a drain plug, but I saw nothing.

What am I doing wrong?

Bob

 

Are you sure your model has a plug. I think not.
Stuart.

 

722.6 got some modified torque converter without drain plug anymore.

 

Then Stuart and Sleepwalker, the question really is how is a complete flush/refill of a 722.6 accomplished? I've read elsewhere that there is a TSB floating around that contradicts the notion that these trans are 'lifetime maintenance free' and that a flush/refill is now 'recommended at the 60K service. Do you know if any of this is true?

Bob

 

Hi Bob,
Would like to see this alledged TSB.
No drain plug will mean that you will not get 100% refill.
Stuart

 

Re: the TSB, you and me both! Another forum is 'flying in tight circles' over this one.

But enough so that I'm going to flush/filter/fill my 722.6 at the 60K service. If there truly is no drain for the torque coverter on this trans, then the only way that I can see getting all the fluid out is via the new 'special pump' that the dealers have for use with the 722.9's. I know they have to make a profit on services, but a trans flush/filter/fill is being reported to be around $400....a tad on the pricey side I believe.

Bob

 

I think it's a moot point. This 500SL has a 722.353 tranny. It was designed before most dealers had the special extraction pump in place. I checked all the service bulletins and MB still recommends a 30,000 fluid/filter change for this vehicle. I'll see if I can get a picture of my setup and post it.

 

,,,,and MB still recommends a 30,000 fluid/filter change for this vehicle,
Would like to see a copy of this PLEASE!
Stuart

 

Well the 500SL DOES have a torque converter drain plug (5mm hex T-wrench or a 5mm hex socket with a 45 degree extension, same as the transmission pan plug) except it's partial obstructed by the exhaust pipe that crosses over at that point. I was able to use a 27mm hex on a long ratchet to rotate the crankshaft and get the torque converter drain plug to line up from under the car. It's easier to get to with the transmission pan off and you won't see it at all unless your head is directly under the pan and your looking somewhat toward the front of the vehicle through the space between the exhaust pipe and the transmission pan. The tricky part was getting the torque converter drain plug back in. Fortunately, the Craftsman T-wrench I had accomodated about 20 degrees of off-center play, but it still took a few tries.

BTW, I checked the Bentley Bible and it says to change the A/T fluid and filter every 30,000 (15K miles in extreme conditions). As a reliability and maintainability engineer for a helicopter manufacturer, I can promise you that it's a sound practice. This nonsense about a sealed transmission is ridculous. A/T fluid MUST be changed...period. This kind of preventive maintenance will save lots of headaches downstream.

 

Bob,
Thanks for this post on how you accomplished finding the torque converter drain plug and R&R steps. Most valuable to the uninitiated!

Bob J-