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Old 05-14-2000, 10:41 AM
stevebfl stevebfl is offline
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844

"Flairing" is a form of "slipping",but totally different. During "Slipping" the drive member is rotating with respect to driven member. This occurs because the pressure pressing them together isn't holding either due to a lack of pressure (usually seal related) or lack of friction material (clutches/band wore out).

During "flairing" the transmission is actually in neatral for the briefest of moments and engages thoroughly once the event is over.

In the case above the second gear band is being released and the fourth gear clutch is engaged. During the event pressure builds against the 3-4 command valve and fills the chamber behind the 4th gear clutch pressure plate. As the fluid builds pressure the drum (pressure plate) starts applying and the piston starts moving. At a point just before clutch lock-up the piston moves against its spring and the pressure to the second gear band servo is dumped. At this moment the car is in neutral (no members engaged). Almost instanly the clutch engages and the event is over.

During normal activity there is overlap during this shift change. What has happened here is that there is no longer overlap actually a gap. This is called shift timing and is built into the hydraulic control system (valve body). The case mentioned above is special because the first models 722.3 transmission had built in deffects to this timing issue (read my first post above).

This condition is usually a precurser to slipping due to wear or lack of sealing of the clutch drum. What you have to remember is that fluid flow unlike electrical flow takes real time (electrical times aren't real {bg}). As the clutch seal wears more fluid pressure is necessary before the drum moves; thus the command valve moves earlier compared to the movement of the drum, the same occur if the clutches are set up too loose(one of this trannies original defects)or worn considerably. In these cases the drum has further to move to take up the play and delays that portion of the shift.

In reguard to M's car, unfortunately the proper next adjustments get complicated and are something akin to "playing music by ear" and I can't hear the tune from this distance. The next move is to get your shifts at a more significant throttle position (or have the vacuum system represent this). This requires making the tranny shift earlier - did you make the control pressure adjustment I talked about above - its just as important as the modulator.

The modulator and control pressure cable adjustments are reversable because the adjustments are quantified. The adjustments of and to the proportioning valve aren't so. I wouldn't try to advise on them without some vacuum values.

Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
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