rich.g.williams
Senior Member
- Joined
- Oct 25, 2009
- Messages
- 753
- Reaction score
- 186
- Location
- Cardiff, South Wales
- Your Mercedes
- C200 Kompressor Coupe 2003
The 722.6 transmission torque converter (TCC) is associated with several lockup clutch problems. Binding problems appear to cause a few different effects as follows:-
-RSN (rumble strip noise)
-bumpy engagement from N to D
-bumpy downshifts from 3rd to 2nd, 2nd to 1st
-lumpy feeling accelerating or climbing hill in lower gears
Invariably the issues are concerned with getting the TCC lockup clutch to fully disengage.
In another thread I mentioned the idea of a daisy chain, meaning that turning the lockup off relies on a lengthy sequence of events.
The daisy chain as follows, the ETC commands NO LOCKUP - current through the Lockup solenoid drops to zero - the Lockup solenoid blocks it's input pressure and vents it's output pressure to sump - it's output pressure drops to zero and turns the TCC Lockup control valve off - the control valve in off position vents Lockup Clutch Piston pressure to sump and it drops towards zero - this pressure is vented to sump fast enough to compensate for any leakage - the TCC working pressure is now higher than the Lockup Clutch Piston pressure so the differential pressure (between them both) fully returns the Lockup Clutch Piston - now the Lockup clutch rings are loose and free to disengage - finally if the Lockup clutch rings are not stuck together the clutch becomes disengaged.
In amongst all that the essential condition for disengagement is:-
TCC working pressure > Lockup Clutch Piston pressure
-RSN (rumble strip noise)
-bumpy engagement from N to D
-bumpy downshifts from 3rd to 2nd, 2nd to 1st
-lumpy feeling accelerating or climbing hill in lower gears
Invariably the issues are concerned with getting the TCC lockup clutch to fully disengage.
In another thread I mentioned the idea of a daisy chain, meaning that turning the lockup off relies on a lengthy sequence of events.
The daisy chain as follows, the ETC commands NO LOCKUP - current through the Lockup solenoid drops to zero - the Lockup solenoid blocks it's input pressure and vents it's output pressure to sump - it's output pressure drops to zero and turns the TCC Lockup control valve off - the control valve in off position vents Lockup Clutch Piston pressure to sump and it drops towards zero - this pressure is vented to sump fast enough to compensate for any leakage - the TCC working pressure is now higher than the Lockup Clutch Piston pressure so the differential pressure (between them both) fully returns the Lockup Clutch Piston - now the Lockup clutch rings are loose and free to disengage - finally if the Lockup clutch rings are not stuck together the clutch becomes disengaged.
In amongst all that the essential condition for disengagement is:-
TCC working pressure > Lockup Clutch Piston pressure
