GMC - CHEVY TRANSMISSION ISSUES - REPAIRS - REPLACEMENT INFORMATION
YUKON - TAHOE - TRAILBLAZER
Over 90% of all Chevy and GMC cars, trucks, and vans made in the last 15 years utilize a 4L60-E transmission. The trucks include the Yukon, Tahoe, Denali, Suburban, Astro, Silverado, Escalade, and Avalanche. The cars include the Camaro, Firebird, Impala, and Corvette. A heavier-duty transmission, the 4L80-E, is primarily found on 2500 and 3500 series trucks and vans.
The 4L60-E has 2 very common problems and a number of less common ones. The common problems are (1) A broken Sun Gear Shell, which will cause a loss of Reverse, 2nd and 4th gear, and (2) A Torque Converter Clutch (TCC) malfunction, which will cause a code P1870 and sometimes a harsh shift from 1st to 2nd gear.
Broken Sun Gear Shell Causes No Reverse
The Sun Gear Shell on these transmissions breaks due to a weakening of the steel during the manufacturing process, causing no reverse. It also causes the loss of second and fourth gear, which is sometimes not noticed by the customer. The Shell is formed by being pressed (literally smashed) into shape by a machine. Small stress fractures occur at an area of the Shell where sharp bends occur. During transmission operation, these fractures have the potential to grow, which can lead to breakage. Since the cracks are microscopic, there is no way to predict the breakage before it happens. The most common vehicles for this problem are the Denali, GMC Yukon, Chevy Tahoe, Chevrolet Suburban, Cadillac Escalade, and Chevy Avalanche. The new aftermarket shell that we install during a transmission overhaul is much heavier and stronger than the original GM part. This new design prevents breakage, but it is not available from General Motors and is not found in GM remanufactured transmissions. This is the reason Suburban can offer a longer warranty with our overhauls.
Torque Converter Clutch Codes P1870
The Torque Converter Clutch (TCC) malfunction is caused by excessive valve wear occurring inside control mechanisms within the transmission and usually is presented as a code P1870. When rebuilding the transmission, we upgrade both of the valves responsible for Torque Converter Clutch operation with newly redesigned valves, manufactured by Sonnax. These new valves prevent failure and ensure proper operation at all times. One of the TCC valves is located within the valve body, while the other is located in the transmission pump. The valve in the pump has a special Teflon seal that compensates for wear that may occur throughout the lifespan of the transmission.
Another concern is the use of plastic accumulator pistons. These pistons are used in many vehicles such as the Tahoe, Denali, Cadillac Escalade and Chevy Avalanche, as well as 2 wheel drive vehicles such as the Astro and Express vans. These newer pistons are inferior in durability to the aluminum pistons that were used in earlier 4L60-E models. Because these Pistons are prone to cracking during usage, we install only aluminum pistons in every transmission overhaul or rebuilt transmission.
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