Trimatic Oper Traps
Originally submitted by T:
The Engine Speed and Road Speed Are Not Directly Related:
Drivers who are new to automatics are often accustomed to the engine speed and the road speed being directly related.
Because an automatic can increase its road speed while the engine RPM remains relatively constant, this can mislead Manual Driver's into thinking that the car has not accelerated or is travelling slower than their perceptions tell them.
As a consequence a driver in this position tends to be all over the power, then all over the brakes.
An automatic only requires the throttle to be opened to about a third, then held there. The gearbox and engine will do all the rest of the work.
The Engine Will Only Crank in Neutral or Park:
The gear lever must be placed in Neutral or Park before the starter will crank the engine.
The Gearbox Dies With The Engine:
When the engine stops all the function of every gear disappears except for Park. Once the engine is stopped the oil pressure in the gearbox stops with it resulting in the gearbox going into Neutral.
The Park position is the only position that works reliably when the engine has been shut off. The vehicle should placed in Park any time the vehicle will be left unattended.
Unfortunately there have been instances where people who are new to Trimatics assume that Reverse will stop the car rolling on a hill and the vehicle has rolled into other vehicles and property.
- Danger - You Can Engage Any Gear Any Time:
Note that a Trimatic can be dangerous because it can be forced into any gear at anytime.
If the engine RPM is high enough at the time of shift a Trimatic can be placed into Reverse when the vehicle is at high speed. A loss of control of the vehicle is assured.
If the RPM is too low for the roadspeed, the Engine will eventually stall, the Oil Pressure will fall to 0 and all the Clutch Packs and the Band will release putting the car into Neutral. Heavy braking from the rear wheels is assured with an associated loss of control.
Similarly, the Park position should only be engaged when the vehicle is motionless otherwise the park ratchet and pawl will be destroyed along with locked up rear wheels and a loss of control of the vehicle.
After Being Left Standing For Long Periods:
If a Trimatic has been left standing unused for more than about a week some strange symptoms can occur.
After making the first start, since the long unused period, upon engaging Drive the vehicle will not move at all.
The Trimatic will then make some groaning and wheezing noises as the car slowly gets moving. Within some tens of seconds the gearbox will begin to behave normally.
The reason for all this is that the oil has drained out of the Oil Pump, the Torque-Converter, the Galleries and anywhere else it could.
The wheezing is the Oil-Pump Primer Valve expelling air from itself and the delay is the Torque-Converter and Galleries being purged of air and finally engaging the single Band and Clutch packs.
All of this is normal behaviour. Just don't let yourself get bitten by being dependant on the gearbox to engage in an instant if you have parked it on a hill or tried to pull into fast moving traffic.
Better to let the gearbox purge itself for a few minutes before staking your life on it.