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2001 deville shifting problems

23374 Views 15 Replies 7 Participants Last post by  wyomingcowboy
Well i noticed my deville has been starting in 1st gear and skipping 2nd gear and shifts striaght into 3rd. If I step on the gas hard to make it down shift it over revs the engine like it was in nuetral, then it finally grabs 3rd again if i leave off the gas pedal. So i have no 2nd gear and no 4th gear I took a fuse out for the transmission and it defaulted it to 1st gear. I think I need a new tranny any thoughts?:helpless:
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The 2001 drivetrain uses a GM 4T80E transmission - if the car is a Base or DHS it uses an economy final drive of 3.11:1 and that's the transmission that must be duplicated. The unit uses a pair of 1-2 and 2-3 shift solenoids with line pressure control engaging 4th (overdrive at 0.681) gear. The solenoid of which you speak - highway loads - is the TCC system - Tprque Converter Clutch. At road load speeds above about 43 mph the TCC engages a viscous clutch in the torque converter to remove most of the last 300 or so rpm of slip between the stator and rotor.

To test the TCC, moderately accelerate through the 4 gears, to about 50 mph....... as you ease off the gas to maintain cruise speed you should hear/feel/see the rpm drop slightly. OK ?? If so, maintain speed with your right foot and touch the brake pedal with your left foot - the brake switch affects TCC and Cruise Control engagement....... as you touch the brake pedal you should hear/feel/see the rpm rise a few hundred rpm. OK ?? release the brake pedal and TCC should engage again. it should take only moderate GAS pedal pressure, for acceleration or passing, to also drop out TCC during the period of power demand.

The car has its own built-in diagnostic code scanner/memory. Study the proper year/model group in the "How to pull codes" sticky just above. P 1860 (either Current or History) is the TCC operating solenoid. IF the car is not subject to emissions you can live with the extra 300 rpm and loss of about 1.5 mpg highway....... but the TCC is an emissions system and the car must pass federal emissions to be sold legally.

To reiterate: You should feel 3 very distinct gear changes during acceleration with a gentle rpm decrease above 43 mph as you ease off to cruise gas pedal.

Heres's a table of car speeds vs. rpm with TCC engaged. (Remember - the base Devilles are speed limited to 112 mph, so disregard the 3.11 graph above that speed)
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