Originally Posted by ChevroletSS
So are you sayin the none computer trans 4L60 has two cables hooked to the throttle body.
The 700R4/4L60 will have a mechanical cable connection from the throttle bell crank that runs down to the transmission. This is the modulator that controls shift points and kick down in relation to throttle position.
The 4L60E will not have this feature connected to the throttle; it gets modulation as digital data from the computer which gets it data from the throttle position sensor mounted on the TBI body and is connected to the computer through the electrical wire harness.
If you have a 4L60E this is the program to follow for the lowest cost solution:
- The existing computer needs the Coolant Temperature Signal (CTS), Throttle Position Signal (TPS), Vehicle Speed Signal (VSS), and the RPM (tach) signal in order to operate the transmission.
- While you can fabricate brackets and a connection to the throttle shaft for your existing TPS, Holley sells a kit that makes this way simpler but it needs to be a Holley with an electric choke. >>> Holley Performance Products Throttle Position Kit for Electric Choke Carburetors*534-202
- The VSS signal comes from the tranny, there is some variation in frequency year to year so keeping your tranny and computer together for your year of truck keeps the speedo tracking with reality and the tranny shifting correctly including the TSS converter lock up.
- The Coolant Temp Signal (CTS) is not the same as what drives the engine temp gauge on the panel, you'll need to use an intake manifold that provides space for two temp sensors unless you move the gauge sender to the cylinder head fitting. This mostly controls TSS converter lock up and prevents 4th overdrive if the engine is running hot and working hard, this protects the tranny from going up in smoke and trust me it will if overloaded in TSS and or 4th gear.
- Since going to a carb would indicate perhaps a performance application then you should also use a stand alone distributor so the computer isn't running the engine on its emissions profile, so an earlier model HEI is needed. Connect its tach lead to the purple and white wire that goes into the old distributor connector of the TBI distributor.
- The tach signal is used for shift points which are modualted by the TPS, it also contributes to converter lock up TSS and 4th gear application.
- Follow what I said for an adjustable fuel pressure regulator with a return. The return is needed to keep the pump from dead heading which will cause it to overheat.
Keep in mind that none of this is legal to do.