Carb with a 200r4
04-11-2019, 05:07 AM
#1
Instructor
Thread Starter
Carb with a 200r4
I bought a 77 corvette that had an EFI set up but couldnt get the thing tuned and couldnt find anyone in my area to help, so I went back to the old carburetor set up.The car shifted in OD fine when I had the computer set up but now that I went old school it no longer does. I searched the internet and (go figure) found conflicting responses. I thought OD was operated via TV cable and lockup was a different function.Do I need a lockup kit? If so, external only, seeing that it went into OD before? I had the TV cable set by a transmission shop so im pretty sure its right. Any ideas?
04-11-2019, 03:13 PM
#2
Melting Slicks
I bought a 77 corvette that had an EFI set up but couldnt get the thing tuned and couldnt find anyone in my area to help, so I went back to the old carburetor set up.The car shifted in OD fine when I had the computer set up but now that I went old school it no longer does. I searched the internet and (go figure) found conflicting responses. I thought OD was operated via TV cable and lockup was a different function.Do I need a lockup kit? If so, external only, seeing that it went into OD before? I had the TV cable set by a transmission shop so im pretty sure its right. Any ideas?
If the transmission is not upshifting into 4th speed (OD) and it did before I would suspect the cable setup. make sure there is no slack in the cable at idle, then at full throttle position it should be fully extended. If you unhook the TV cable from the carb and pull on it you can feel the point where it starts to move the valve in the transmission, compare this to where its fitting on the carb is at idle. Cable set up is very important because the throttle position affects the transmission shifting behaviour as well as the oil pressure used in the transmission to hold the clutches. Slack cable can lead to transmission clutch damage from slipping.
Was the EFI unit controlling lock function of the torque converter? If it was you are going to have to add a lock up kit to enable this function again.
OD function is indeed controlled by the TV cable, and the torque converter lock function is electrically controlled separately. Generally when the lock function is computer controlled the pressure switch used inside the transmission is a normally closed (remove power to close switch) unit if my memory serves me correctly. This has to be changed to a normally open unit for non computer applications so you will need to investigate this as well. A 2004r transmission often came with two pressure switches fitted that enabled locking of the TC both in 3rd or 4th speed. I believe most here, me included only use the lock function on 4th speed (OD).
