5sp auto gearbox - does it have lockup?

[tpt]

Do the mb 5 sp auto gearboxes fitted to an 05 e220 cdi have the auto lockup feature? if so, how does this work? at what speed does it lock the drive to the engine?

 

[type49]

Yes it has a torque coverter lock up. It is solenoid activated from inside the box. Don't know at what speed you could get it to lock in. It has a lot to do with load as well as just speed. Why do you ask??

 

[tpt]

I ask becasue i saw something in another thread that a person was getting poor fuel economy and part of the reason was a lack of lock up. I've been trying to figure out how the gearbox works too (you know planetry gears and all that). I guess it has a significant bearing on fuel economy?

 

[television]

Very seldom does the 722.6 lock up all of the time, it is mainly used for engine braking and in 5th its a partial lock up

 

[tpt]

partial lock up? I thought it was binary - on or off? How would partial lock up work?

 

[tpt]

Also, the other day i was in a VW passat taxi which had the DSG box - it was truely weird in the way it worked. Clearly automatic, but the changes were instant. Loooking at the rev guage confirmed this - none of the usual slow and steady drop in the needle from one cog to the next; rather an instant (and it looked severe!) drop from say 5000 to 2500 - can this be good for the enging? when do MB bring their DSG box out?

 

[st13phil]

Very seldom does the 722.6 lock up all of the time, it is mainly used for engine braking and in 5th its a partial lock up

Hi Malcolm could you elaborate on this further, please? And am I correct in thinking that my 5-speed W204 has a 722.6 'box in it? It feels to me as though the torque convertor locks up in all 5 gears on that, but I could be wrong

 

[stumpy]

Also, the other day i was in a VW passat taxi which had the DSG box - it was truely weird in the way it worked. Clearly automatic, but the changes were instant. Loooking at the rev guage confirmed this - none of the usual slow and steady drop in the needle from one cog to the next; rather an instant (and it looked severe!) drop from say 5000 to 2500 - can this be good for the enging? when do MB bring their DSG box out?

I owned a DSG equiped car a little while ago and in some ways the box was amazing but in truth, a proper auto, or a proper manual is better. Mine was a Tdi and the initial pick-up from rest was a bit lazy when you needed a good dollop of acceleration. Also, the kickdown as you describe can drop half the rev range and 3 gears instantly. I think the engine could cope ok, but my neck couldn't. The resulting burst of acceleration can take you and your passengers by surprise. I also hear of quite a few reliability issues with VAG DSG.

 

[st13phil]

Also, the other day i was in a VW passat taxi which had the DSG box - it was truely weird in the way it worked. Clearly automatic, but the changes were instant.

I drove a SEAT Leon with a DSG box the other day and you're right - the gearchanges are a spooky sort of experience. There's a good explanation of how the DSG box works that I found here if you're interested. Basically the instant gearchanges are achieved by having two clutches, one engaged and one disengaged, connected to two concurrently engaged but different ratio drive paths through the gearbox. To change gear one clutch disengages and the other engages simultaneously which means that there's no loss of drive at the shift point. Clever stuff.

 

[television]

Hi Malcolm could you elaborate on this further, please? And am I correct in thinking that my 5-speed W204 has a 722.6 'box in it? It feels to me as though the torque convertor locks up in all 5 gears on that, but I could be wrong

Yes you have the 722.6 box it does not lock in top,,if you slightly press the throttle you will see the revs change with out the car speed changing.

I have a paper on this and I will try and find it

 

[st13phil]

Thanks Malcolm, I understand what you mean now: once in 5th then the tacho will rise / fall a total of about 50 - 100rpm between the overrun and light throttle which it doesn't do in any of the lower gears. I'd definitely be interested in any info you have that explains the why's and wherefore's.