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1955 Corvette: Service Bulletin: Upshift at Part Throttle

Subject:   Upshift at Part Throttle
Model and Year:   1955 6-Cylinder Powerglide
Source:  Chevrolet Technical Service Bulletin
Bulletin No:   DR - 192
Section:   VII
Date:    January 31, 1955

TO:  ALL CHEVROLET DEALERS

In cases where the 1955 6-Cylinder Powerglide Units upshift in the 25 - 28 MPH range on part throttle, and it is desirable to have the upshift at 12 - 18 MPH for best fuel economy, particularly in Metropolitan areas, a new Throttle Valve Control Outer Lever and Control Rod should be installed and linkage readjusted.

The new Control Rod and Outer Lever went into production at assembly plants during week of 1-10-55.

PARTS

Description New Part No. Old Part No.
Throttle Valve Control Outer Lever 3720325 (Change in angle) 3710634
Control Rod 3715711 (Shortened) 3710632

THROTTLE VALVE LINKAGE ADJUSTMENT

  • Set engine idle at 425 RP.M. in drive range.
  • Remove old and install new Control Outer Lever and Rod leaving rod loose at lever end and lever adjusting bolt slightly loose for adjustment.
  • Remove top bolt on rear edge of low and drive valve body.
  • Rotate the Throttle Valve Control Lever on the transmission counter clockwise to the open throttle position which is a definite stop.  Hold the lever in this position to the open throttle position which is a definite stop.  Hold the lever in this position and with the Throttle Valve Outer Lever Positioning Gauge J-5906 set to 6", clamp the outer lever so that the pins on the gauge will enter the upper bolt hole on the rear edge of the low and drive valve body and the rod hole in the control outer lever.
  • Connect rod to control outer lever.
  • Disconnect the carburetor throttle valve lever rod at the carburetor and the rod running from the dash bell crank to the bell crank at the cylinder block at the block end.
  • Adjust the carburetor throttle valve lever rod for free entry into the swivel pin in the carburetor throttle valve lever with the throttle valve in the wide open position.
  • Then, with the carburetor throttle valve held in the wide open position and the accelerator fully depressed, adjust the remaining rod at the bell crank on the cylinder block for free entry.
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