A/T - New Transmission Calibrations

File In Section: 7 - Transmission

Bulletin No.: 87-71-69

Date: July, 1998

INFORMATION

Subject:
New Transmission Calibrations

Models:
1998 Chevrolet Camaro
1998 Pontiac Firebird
1998 Chevrolet and GMC G-Van, C/K, M/L, S/T Models
1998 Oldsmobile Bravada
with HYDRA-MATIC 4L60-E Transmission (RPO M30)

All 1998 light duty trucks and V-6 F-cars equipped with 4L60-E received a new transmission calibration called Electronically Controlled Capacity Clutch, commonly referred to as "EC-cubed." This revised calibration will partially apply the torque converter clutch (TCC) at a lower vehicle speed than past calibrations and at a controlled slip rate. This revised calibration is intended to increase fuel economy and reduce NVH (Noise Vibration Harshness).

One feature of EC-cubed that customers are most likely to notice is increased engine braking on a closed throttle decel while in 4th gear. Prior to EC-cubed, the TCC was released whenever the throttle went to zero so in 4th gear the vehicle had very little engine braking. On an EC-cubed vehicle, the TCC will stay locked at zero throttle until the brake is applied and 4th gear engine braking will be noted. EC-cubed is applied when engine torque is below 200 foot pounds, above 200 foot pounds TCC is locked-up.

The amount of engine braking will vary depending on engine and vehicle speed and generally is less than that experienced on a comparable vehicle equipped with a manual transmission. Also, little or no engine braking will occur until the engine goes into Decel Fuel Cutoff. The amount of time needed to enter Decel Fuel Cutoff will depend on engine operating parameters and calibration.