Re: [A/S] Tranny lock-up kit and exhaust brake

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

Spencer,
 The Torque Converter amounts to a special oil pump that has a fair
amount of internal leakage. When a hydraulic system pumps its own fluid
over and over, the oil gets HOT. To alleviate this (and make the vehicle
much more fuel-efficient), today's automatic transmissions have a clutch
in the torque converter (TCC) that "locks up" when the vehicle achieves
a certain speed in the higher gears. If you have a tachometer, it's very
easy to 'see' the operation of the TCC. Usually, removing your foot from
the throttle will cause the TCC to unlock.

Of course, when going downhill, the TCC unlocks, but is trying to pass
torque from the driveshaft to the engine (engine braking). This causes
heat (see above). Forcing the TCC to remain locked until the vehicle is
at a very slow speed (below 25 MPH) will eliminate the heat buildup and
give much better engine braking.

The term "shear" in this context refers to that internal pumping
referred to above.

                                         <<Jim>>