Tuesday, October 14, 2014

Tech Tips and Troubleshooting for High Performance Transmissions: Under Pressure

BTE recommends that every racer monitor their transmission's line pressure and regard it as important as the oil pressure in their race engine. Automatic transmissions rely on the pressurization of their internal systems to operate properly in each gear range. Forward, reverse, and gear shift quality are largely dependent on the level of hydraulic pressure regulated by the transmission.
  • In a race-prepped powerglide transmission, BTE recommends at least 210 to 255 PSI in all gears. These circuits can be measured at the transmission servo port and the reverse port. The increased pressures can be achieved by installing a stronger spring in the valve body's pressure regulator or by installing a complete valve body kit, like BTE's Top Sportsman valve body. Higher pressure reduces shift lag and helps maintain friction clutch pack life.
    • The cooler circuit should also be measured. In a powerglide, most setups should see anywhere from 45 to 100 PSI. This will vary depending on the input shaft, pump, and converter combination.
  • Transmission line pressure testing is also a great way to diagnose the internal condition of a transmission. Inconsistent pressures or lower than expected pressures can indicate an internal leak or broken seal. If pressures are slow to build when the engine RPMs are increased, this may also indicate a worn or failing pump. We recommend using the BTE high volume pump for more consistent oil pressures. As pressure varies, the car's performance will be inconsistent.  For a bracket racer, this is an essential test to perform on an ongoing basis.
Consistent and high hydraulic pressure will keep your high performance racing automatic transmission going strong weekend after weekend. As always, contact us for specific recommendations for any custom racing transmission configuration.

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