Don’t worry about the pressure at
idle: If the gauge shows an increase in pressure in reverse, then drops back to a lower value in park, it proves that the EPC boost valve, pressure regula- tor valve, and pump slide are moving freely. If you determine that the trans has
line boost at 1200 RPM in reverse, check for these conditions: • bad EPC solenoid • plugged EPC boost feed hole (figure 3)
• plugged EPC filters • actuator feed limit valve problem
Figure 3 If the line pressure doesn’t change
between park and reverse, check for these conditions: • stuck EPC boost valve • wrong size EPC boost valve and bushing combination
• stuck pressure regulator valve • stuck pump slide
Note: A leak in the reverse circuit
can create no boost or cause pressure loss in reverse.
Review and Diagnosis This 4L60E had reverse pressure
boost at 1200 RPM, so we know the pressure regulator valve, slide, and EPC boost valve were working prop- erly. It had no line boost in drive range, but PCS current was dropping properly. This leaves three possibilities:
1. a bad EPC solenoid 2. an EPC boost feed hole plugged or missing
3. an actuator feed limit valve prob- lem
The EPC boost feed hole was
plugged with dried soap from the water-based parts washer (figure 3). And once again, examining and evalu- ating the data provided a quick answer to a difficult situation. So remember: When you’re faced
with a transmission problem, think in terms of how it works, not parts replacement. And until next time, always keep your shifting business headed forward.
Since 1977, INA has been the trusted partner and supplier to vehicle manufacturers worldwide, producing over 50 million tensioners annually.
From Acura to Volvo, INA belt tensioners cover the most extensive range of European vehicles and a wide range of U.S. domestic applications. Our expanding coverage of Asian applications reinforces our commitment to providing a growing line of high quality products to the import specialist market.
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5370 Wegman Drive Valley City, OH 44280 Phone 800 274 5001 Fax 330 273 3522
www.Schaeffler-Aftermarket.us
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The best import tensioner program just got even better!
GEARS March 2012
27
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