MB World members,

I am hoping to solicit some advice from those who've walked this path already. I recently stumbled across the subject of (select) 722.9XX transmissions with compromised pumps - that generate a whining/whirring sound. My 2009 W221 S63 has had a mild whining/whirring sound since I purchased it a year ago (34K miles then, 55K now). It's not terribly noticeable, in fact, many who ride in the car say they can't even hear what i'm talking about. But I hear it, and that's all that matters! Previous attempts to pinpoint the sound have gone without success. I purchased a mechanic's stethoscope and listened to every auxiliary on the front belt (power steering, water pump, alternator, belt tensioner, and AC pump) - nothing. I listened to the cam covers all the way from front to back on both banks (M156), nothing. I listened to the fan motor, nothing there either.

The noise is only present when the car gets up to full working temperature, but isn't of the same magnitude at all times when it does. It seems to be worse when commuting home in the afternoon heat (Houston, TX) than in the pre-dawn early morning drive towards work (~40 miles away). The sound is engine speed dependent - not vehicle speed dependent. The noise is exhibited in all driving modes (C, M, and S), and only does it when moving (the sound is NOT replicated in neutral.) On a scale of severity I would put the sound at a 3.5/10, and from what I can tell, is getting no better or worse as I continue to add miles to the vehicle.

Some forum members have written this noise off and claim it is just a 'normal' sound from this engine/transmission combo. Some have described the sound being much louder and eventually leading to pump failure as the bushing becomes bound to the shaft and scores the face of the pump housing. Others have REALLY bad whining noises, especially on start-up (Glen pegged this one from one members post and matched it to a youtube post of the EXACT same sound) but this is NOT the sound mine is making.

So all this said - could anyone suggest a diagnostic method that would prove/disprove whether this issue is indeed most likely the transmission pump?

If it is the transmission pump I would like to get one step ahead by buying a used 722.9 unit and rebuilding it, to keep as a a shelf spare. My questions from there are:

- will any 722.9 unit work as a donor or do I need to find a 722.907 (a VIN report suggests this is the unit I have in my car a 722.907 02 082833 (VIN#WDDNG77X99A273786)

- Is it true that MB redesigned the transmission pump in the 722.9? If so, does anyone know when this was done, and if my vehicle was pre/post the switch?

- Is there an official part number for a full 722.9 rebuild kit? Surprisingly, there seem to be very few 'complete' rebuild kids available - mostly on Ebay

- If there isn't, could anyone recommend a respected manufacturer/retailer of master rebuild kits (seals, clutch plates, steels, pump, gaskets, etc.....)

- If I do buy and rebuild a used transmission, will it plug and play into my car or will I need to flash it to match my own, or could I change my existing one out onto the rebuilt unit

Lots of questions but i'm trying to stay out of the wrong rabbit holes! Any advice would be much appreciated, thanks in advance.

Simon

 

So your transmission 722.9 (7 forward gears, 2 reverse) is coded to your car. If you buy a used one, someone with Star or obviously the stealership has to recode to your car.

I have a 2006 R class with the transmission literally apart on my work bench right now. The transmission pump failed. It's the pump with the bushing (old pump) and it's gouged/totally worn. The other obvious indicator it's broken is the 2 inside teeth are sheared off. The two teeth fit into the Torque Converter so the TC can drive the pump. I did not have any crazy noises, but as you've probably noticed from people's experiences, it can vary.

How will you know for sure? Pull the tranny and inspect the pump - that's the only sure fire way. Some get broken gears or just the worn bushing or combinations. My pump gear teeth were fine, no cracks, but it can happen.

I've heard some say you can have your old pump machined to accept the needle bearing that's in the improved pump. Since the 2 key teeth in mine were toast, I ordered a new one from FCP euro and they confirmed they carry the updated part that has the needle bearing instead of the bushing.

Oh and sorry I don't know the exact year they switched the pump from bushing to bearing - but it's going to depend on model anyway. Hopefully someone with your exact year and model can chime in.

Good luck man.

 

Hey Simon,
It seems I am having the exact same issue as you, on my 2008 S63.
Were you able to resolve it? Please let me know, thank you!

 

Sorry for the slow response. YES! It turned out to be nothing more than the transmission mount (rear motor mount, as it's sometimes referred to). Bought an OE one (Cortico brand, link below) from FCP Euro and it took care of it instantly. All done for under $100 on my driveway. As the mount gets older/used the the weight and progressive torque effects cause the rubber section to compress and it creates a minor deflection in the engine/transmission and prop shaft alignment. Simple hand tools, a jack and jack stands are all that's needed - or in my case at least.

Transmission Mount

PN# 2212400918

Best of luck,

Simon