Mercedes 7G auto transmission failure

[JOEPRO]

Friday was an interesting day for me! Drove my w221 S320 CDI 722.9 auto transmission to a site 40 miles from home. All fine.

Then on leaving the carkpark to head to the office I noticed it a bit sluggish to change gears and within 3 mile it suddenly lost gear (quiet, no noises or grinding etc at all)

I coasted it off the road safely and got a friend to recover it to my house. I have MB star diagnostic laptop and there are no new trouble codes. I say no new ones as it always had these codes which never caused it an issue:



On the dash it goes into drive & reverse etc OK. Revs up but will not move at all. Zero movement car just sits there.

Reset codes and same.

I reckon she has had some sort of complete and sudden oil pump failure. The live data doesn't let me see the oil pressure values but I'll loosen a cooler hose and see does it have pressure - I'd guess no as that is really the only thing that would cause it to have no drive at all.

Shame as I was thinking of changing this car which is my daily driver. It has full factory amg kit etc and is in very good condition. 133k miles full service history. Had it 3.5 years, great car.

So looks like I'm in for alot of work! I can rebuild my own auto transmissions, have done successfully before. Ideally I'll get away with pump replacement in this one if it hasn't shed metal in the oil.

The trans was only serviced 4 months ago by me with all genuine parts so that's why I believe there is fluid in there and correct level as no signs of sudden oil loss. So that £120 oil fill will be needed again. Car isn't worth very much but I have no energy to break it for parts and don't want it lying here either. So repair it is. Darn it! Aw well

Going to look at a replacement car tomorrow- a w205 c220 2017 year. As I said I was going to replace this car just didn't plan on it being this sudden.

 

[Pigeon_Droppings2]

The trans was only serviced 4 months ago by me with all genuine parts

I had big troubles with my Volvo auto box after I changed the fluid.

The new fluid had detergents that cleaned the box...all the crud stopped the solenoids working.

 

[Ubique]

Oddly enough, we had a Merc. with the same transmission in last week, oil pump failed - you could see the mounting bolts 'bleeding' through the bellhousing lower bung. - 'sparkles' in the oil sample so £5k for a replacement transmission or £2.5k for a refurb sourced locally.

 

[Morrisman]

I’d start with checking the fluid level, if such a thing can be done? You could have a hole in a pipe or the cooler, and left several litres of fluid on the road.

 

[Ubique]

I had big troubles with my Volvo auto box after I changed the fluid.

The new fluid had detergents that cleaned the box...all the crud stopped the solenoids working.

Probably well overdue then.

 

[Pigeon_Droppings2]

Probably well overdue then.

Volvo reckon the oil is good for the life of the box .

There's a recommendation of just changing 1l at a time...which is what I did but it didn't help.

 

[JOEPRO]

Oddly enough, we had a Merc. with the same transmission in last week, oil pump failed - you could see the mounting bolts 'bleeding' through the bellhousing lower bung. - 'sparkles' in the oil sample so £5k for a replacement transmission or £2.5k for a refurb sourced locally.

£5k being the supply cost of new genuine MB trans?

£2.5k was that labour included?

I will repair this one myself so no labour cost or worst case spend about £300 on a used transmission if the original unit is too far gone.

I also advertised the car as spares or repair so who knows it may end up selling if someone else wants to take it on

 

[JOEPRO]

PS in many cases transmission refurbs are a bit of a joke!

People assume that they are not serviceable at all by a decent mechanic. And that when you pay for a "full refurb" you will be getting all new frictions and wear parts. Sometimes they do replace all but I'd say that's very rare. In most cases the issue is isolated to a particular area and all original frictions that are serviceable go back in.

Indeed on Mercedes 722.6 transmissions I rebuilt all they needed was the frictions re - shimmed as they were still within new spec. (There are different thickness snap rings available to set the gap)

All new aftermarket frictions for a 722.6 are thinner than the genuine ones. So if they replaced all of them they could reduce the life of the transmission!! Anyway rant over, I think transmission rebuilds are overrated and overpriced and I am glad I have the manuals and specialist tools to do my own rebuilds on Mercedes boxes.

 

[roofman]

I had big troubles with my Volvo auto box after I changed the fluid.

The new fluid had detergents that cleaned the box...all the crud stopped the solenoids working.

Same thing happens to the E60 535 BMW when you change the oil for life.

 

[Ubique]

£5k being the supply cost of new genuine MB trans?

£2.5k was that labour included?

I will repair this one myself so no labour cost or worst case spend about £300 on a used transmission if the original unit is too far gone.

I also advertised the car as spares or repair so who knows it may end up selling if someone else wants to take it on

£5k (in rough numbers) is a M-B replacement only, labour is likely to be 2.5 hours inc. coding - it'll be DAS3 so you'll need the 'blue key'. Obviously the labour will be the same for either option, bear in mind the M-B unit is supplied 'wet' whereas a refurb may not be.

 

[Ubique]

Volvo reckon the oil is good for the life of the box .

Well they were correct.

 

[JOEPRO]

Mine could have done something like this if the pump has indeed went out. I will only really get looking at it next Saturday when I'll likely remove the trans after checking if it has no oil pressure and if there is oil in there.

722.9 Pump Failure - Transmission Digest

A common and well-known failure with the 722.9 transmission is the way the pump bushing seizes to the converter neck (Figure 1).

www.transmissiondigest.com

 

[Ubique]

Annoyingly, unlike other manufacturers I can't find a 'safe from' date or VIN, possibly on VeDoc, I'll have a look during the week

 

[JOEPRO]

I pull trans parts and pumps at breakers yards. They sell perfect used pumps to me for pennies! So I believe I already have a couple of the new style roller type oil pump for these transmissions on the shelf.

And a mild steel repair plate insert takes care of the belhousing damage. So alot of assumptions here but if this is what happened my only real parts issue would be a torque converter if the nose of mine is damaged.

 

[JOEPRO]

Yep - here are 3x spare suitable pumps perfect used on my shelf. Bushing style but will be fine. I have roller types around too somewhere.



I have around 15 spare transmissions too. Some very rare and very low miles ones too. But no 722.9

3 of the spares as example, they are tucked in everywhere!



I also have about 6 spare engines and 44 headlamps maybe? And hundreds of other parts maybe biggest private MB parts collection in UK. (Yes I have issues but it pays off when crap hits the fan I have the parts I need sitting here)

 

[Blobber]

You have me worried now
Whats should the boxes do mileage wise?

 

[JOEPRO]

You have me worried now
Whats should the boxes do mileage wise?

If mine does turn out to be what I think it is, failed oil pump then that is really quite rare IMO. I have had 722.6 MB auto boxes with 250k miles on them in my ownership and still going strong no issues before I sold on and the car likely still going.

So don't worry about MB auto transmissions for the most part they are very reliable. Water contamination kills some of them from faulty radiators some years back. And other failures are rare overall they take alot of abuse and keep going usually.

I don't class conductor plate replacement as a major issue fwiw so I am referring to major issues above.

 

[Turbo]

You do realise this is your fault. You are now spending all your free time rebuilding stihls so the mercs are feeling neglected.
They decided the best way to get your attention was to hobble the daily driver.
It's just as well you have a fleet of cars to pick a replacement from!

 

[JOEPRO]

You do realise this is your fault. You are now spending all your free time rebuilding stihls so the mercs are feeling neglected.
They decided the best way to get your attention was to hobble the daily driver.
It's just as well you have a fleet of cars to pick a replacement from!

I was thinking if strapping a BR800 to either side of it and drive around town shouting "I don't need no transmission" but maybe better just fix it properly

 

[Ubique]

722.9 (01) part numbers changed in Feb 2016, I can't see the full supercession as my D5 had been deactivated and I'm now slumming it with a C5....