*Please Help* Gearbox slipping between 3-4th Gear. 722.9G PLUS

[Adam101]

Hi, I have a really annoying problem that I just cant seem to find the solution too. I have a 2013 Diesel C220 with a 7G Tronic plus gearbox.

When the car gets to operating temperature, there is a jump in RPM before engaging in 4th gear. Sort of like a slipping manual gearbox. Once it is in 4th Gear the RPM's start slightly bouncing especially when going uphill or light on the throttle.

Also in first gear, the RPM's do drop before then quickly rising and going into second.

All other gears work perfectly fine. I have had the TCU scanned using STAR no faults showing. Also changed the gearbox oil and filter. Still no luck.

Note this is much worse when the car is warm, when it is cold it isn't very noticeable.

Please could anyone help before I end up changing the whole box/

 

[ernie]

Hi, I have a really annoying problem that I just cant seem to find the solution too. I have a 2013 Diesel C220 with a 7G Tronic plus gearbox.

When the car gets to operating temperature, there is a jump in RPM before engaging in 4th gear. Sort of like a slipping manual gearbox. Once it is in 4th Gear the RPM's start slightly bouncing especially when going uphill or light on the throttle.

Also in first gear, the RPM's do drop before then quickly rising and going into second.

All other gears work perfectly fine. I have had the TCU scanned using STAR no faults showing. Also changed the gearbox oil and filter. Still no luck.

Note this is much worse when the car is warm, when it is cold it isn't very noticeable.

Please could anyone help before I end up changing the whole box/

I was hoping somebody with practical knowledge of these boxes would come on to help! However, from what you say, it seems that the box is 'flaring' between some of the gears when shifting. there are a number of potential causes of this but unless the box has done a huge mileage, I would get the car to a specialist to check out the problem; maybe a valve block is all it needs and not another box, which if second-hand, could be just as bad.

Ernie

 

[Adam101]

Hi, thanks for you reply.

 

[Adam101]

I was hoping somebody with practical knowledge of these boxes would come on to help! However, from what you say, it seems that the box is 'flaring' between some of the gears when shifting. there are a number of potential causes of this but unless the box has done a huge mileage, I would get the car to a specialist to check out the problem; maybe a valve block is all it needs and not another box, which if second-hand, could be just as bad.

Ernie

Hi, thanks for you reply. Mileage isn’t considerably high. It’s on about 90k, ive taken it to two gearbox specialists who tell me that the gearboxes on these never go wrong, usually only the TCU but they can refurbish it for nearly 2k :|

I could put in a used one and swap the TCU over for a third of the price, but again there’s always a risk with a used box.
Any chance it could be just the torque converter?

 

[geoffus]

Didnt we have someone here with a similar problem ?
After going through the normal procedures of changing ATF etc it was cured by resetting the gearbox adaptions.

Pre facelift E63 AMG 7g+ autobox issue. | AMG Lounge

I've only had my 2012 E63 AMG prefacelift a few months now, initially everything worked perfectly. The car has just over 50k with full Mercedes service history. I couldn't see anywhere that the gearbox had been serviced (oil & filter change) so I had this done at a local gearbox specialist do...

forums.mbclub.co.uk

 

[Adam101]

Didnt we have someone here with a similar problem ?
After going through the normal procedures of changing ATF etc it was cured by resetting the gearbox adaptions.

Pre facelift E63 AMG 7g+ autobox issue. | AMG Lounge

I've only had my 2012 E63 AMG prefacelift a few months now, initially everything worked perfectly. The car has just over 50k with full Mercedes service history. I couldn't see anywhere that the gearbox had been serviced (oil & filter change) so I had this done at a local gearbox specialist do...

forums.mbclub.co.uk

Gave that a try, still no luck I’m afraid. I’ve noticed there’s a slight whining noise coming from the gearbox when down and up shifting. Confused

 

[alexanderfoti]

Gave that a try, still no luck I’m afraid. I’ve noticed there’s a slight whining noise coming from the gearbox when down and up shifting. Confused

Either low fluid level, blocked oil filter/cooler or the pump is failing.

Does it take a long drive to go into d or r?

 

[Adam101]

Either low fluid level, blocked oil filter/cooler or the pump is failing.

Does it take a long drive to go into d or r?

No goes into D and R straight away. I’ve had the oil changed (was doing it before oil change too) made sure to change oil in the TC aswell also put in a new filter.

Which pump are you referring to sorry?

 

[alexanderfoti]

No goes into D and R straight away. I’ve had the oil changed (was doing it before oil change too) made sure to change oil in the TC aswell also put in a new filter.

Which pump are you referring to sorry?

The gearbox oil pump inside the box. Whining noises are never good though

 

[alexanderfoti]

What did the old oil and bottom of the sump look like.

 

[Adam101]

What did the old oil and bottom of the sump look like.

Old oil was quite dark to be fair, didn’t smell burnt though. Sump was clean, no metal shavings or metal pieces around bottom. I was fairly surprised. The TCU did have some pen marks on it, so I presume the previous owner has either had it repaired or changed.

I think I might just risk putting in a used box with a TC and just swap the TCU over. What do you reckon?

 

[alexanderfoti]

Old oil was quite dark to be fair, didn’t smell burnt though. Sump was clean, no metal shavings or metal pieces around bottom. I was fairly surprised. The TCU did have some pen marks on it, so I presume the previous owner has either had it repaired or changed.

I think I might just risk putting in a used box with a TC and just swap the TCU over. What do you reckon?

Probably not a bad idea. If you want to keep the car then might be an idea to get it rebuilt.

 

[Adam101]

Probably not a bad idea. If you want to keep the car then might be an idea to get it rebuilt.

Fair point.
Out of curiosity any chance of it being just the torque converter? What type of symptoms do they tend to show when failing?

 

[alexanderfoti]

As its only between 3rd and 4th it's unlikely to be the tc

 

[Adam101]

As its only between 3rd and 4th it's unlikely to be the tc

Ah I see, cheers for your help mate. I’m going to try seeing if I can source a low mileage box and most likely just pop that on.
I’ll keep the thread updated!

 

[Jobsworth]

A lot of what you describe gives me a sense of torque converter problems. If you haven’t already done it, drop the valve block and check the little thimble filter. Very few people are aware of this.

 

[Jobsworth]

Edit to say, I’ve put my glasses on now. Nothing is common to the 1-2 change AND the 3-4 change. The K2 clutch is engaged for the 3-4 change. Might be worth a look at the solenoid that controls that clutch. It could still be worn plates, but it’s a full strip to check.

 

[Jobsworth]

If you aren’t familiar with the powerflow diagram for the 722.9, there are always three items locked to engage a gear. Gearchanges, up or down, involve the release of one item and the locking of another. The diagram shows what’s locked for each gear. B’s are brakes, K’s are clutches.

 

[Adam101]

Edit to say, I’ve put my glasses on now. Nothing is common to the 1-2 change AND the 3-4 change. The K2 clutch is engaged for the 3-4 change. Might be worth a look at the solenoid that controls that clutch. It could still be worn plates, but it’s a full strip to check.

Ah, that makes sense. I think you might’ve cracked it. Must be something to do with that K3 either the solenoid or the clutch itself inside the box. I’ll try changing the solenoid first and I’ll check that small filter. If all fails then a new/used box it is. I’m just hoping it’s as simple as just swapping the TCUs over the need of extra coding etc

 

[Jobsworth]

If you do go the secondhand box route, the numbers must match exactly. The ratios differ a lot, and if they don’t match it’ll be in limp all the time