|Throttle Valve (TV) Cable System|
Scott Simpson - Scott231@Juno.com
|Theory of Operation|
|The T.V. cable used on the 200-4R transmission controls line pressure, shift point, shift feel, part throttle downshifts and detent downshifts. The T.V. cable operates the throttle valve lever and bracket assembly inside the valve body.
The Throttle Valve Lever and Bracket Assembly serve two basic functions:
If the cable is not connected or broken, the T.V. lifter rod will not move from its normal position which holds the T.V. exhaust check ball off its seat. The T.V. lifter rod will drop down to allow the T.V. exhaust ball to seat only if the cable is broken, disconnected or out of adjustment. With the transmission pan removed, pull down on the T.V. exhaust valve lifter rod and the spring should return to rod to its normal up position. If the throttle valve lever and bracket assembly or lifter rod binds or sticks so that the T.V. lifter rod cannot lift the exhaust ball off its seat, high line pressures and delayed upshifts will result (Note that this is what we will try to accomplish, tighter shifts). The T.V. lifter rod must not be bent or it will not function correctly.
|On the driver's side of the intake plenum is a bracket holding 2 or 3 cables:the Accelerator cable, T.V. cable, and if you have Cruise, the cruise controlcable. The T.V. cable has "ridges" on the cable housing and routes behind and down the engine to the passenger side of the transmission. Note the metal Brass colored, "D-shaped" tab in the center of the bracket, this is the readjustment tab. Take note of the T.V. cable position (number of exposed ridges).
With the engine off, depress and hold in the readjustment tab. Pull the cable housing towards the firewall 3 or 4 clicks and release the readjustment tab. While you watch the cable housing travel, have someone push the accelerator pedal to WOT. (Yes you can rotate the throttle lever by hand but by using someone's foot you are duplicating the actual throttle movement achieved while driving the car.) The cable housing will "ratchet" forward towards the radiator. This is the "GM recommended" setting. If your T.V. cable was out of adjustment, the number of exposed ridges will have changed.
As a benefit to those desiring firmer shifts, you can attain higher shift points by moving the T.V. cable back towards the firewall one more "click". Try this and see if the cable housing will not ratchet back out when you press the accelerator to WOT. A worn out cable housing or adjustment mechanism may only let you go to the "GM recommended" setting. You should also know that by delaying shifts on a transmission whose clutches are already "shot", this will accelerate the deterioration of the transmission.