Oftentimes, all that is required is a little more TV-cable travel to make everything work. This spring-loaded trick is available from most transmission shops. It pulls the cable outward slightly at just off-idle and then when approaching wide-open throttle, the spring collapses and allows the throttle to fully open.
Watching TV
Jim MacCallum, via CarCraft.com: To replace my '78 Monte Carlo, which had finally deteriorated beyond being easy to repair, I acquired an '85 Monte Carlo SS. The powertrain is a 305, which came attached to a 200-4R, Chevy's early four-speed automatic overdrive. These have something called a TV cable. When I first drove the car, the First-to-Second shift point occurred around 3,000 rpm at about 30 mph and was such a hard shift that I was concerned it would tear up the trans. Second-to-Third would not occur until I hit 35 mph or better, and if I got the shift and then tried to slow down, it would pop back into Second and wind up the mill like crazy. Upon discovering that the resident carb was a Quadra-bog and not the original one at that (I found its corpse in the trunk), I decided to swap it out for a Holley 650 Spreadbore I had and knew would fit the existing manifold. At the same time, I pulled the tranny pan and dumped the old oil and changed the filter. The filter was about history and the oil was about at the point of turning brown but did not smell burnt, and there was no significant debris in the bottom of the pan beyond the normal amount of black goo that accumulates there due to wear and tear.
This maintenance did not solve the shift issue, so after doing some reading, I concluded that the TV cable was the culprit and that it had to be reset to work correctly with the Holley. Using the factory manual as a guide, I reset the cable and the shift points dropped dramatically, but now the tranny shifts like Second and Third are slipping and the next solid gear seems to be either Third or Fourth. Moreover, unless I pedal the throttle, any kind of hard acceleration causes the TV cable to try to reset itself back to the old high-rpm shift points. My questions at this point are: Do I need to return the TV cable setting? Is there a happy medium? Is the cable damaged and needs to be replaced? I have a Turbo 350 along with the correct crossmember and driveshaft that I salvaged from my old ride. Would it be cheaper to yank the 200-4R and plug in the 350? Would a 700-R4 drop in, and what would I have to do to make it work besides needing a stand-alone computer?
Jeff Smith: Just for the record, many knowledgeable transmission people we have interviewed think the 200-4R is an exceptionally durable trans and many recommend this trans over a 700-R4. Jim, you are suffering from the same kind of problems that afflict most owners of modified cars who attempt to use either the 200-4R or the 700-R4 transmissions that employ a TV- or throttle- valve cable. The TV cable replaced the older transmission-control style that sensed load with a vacuum-modulator valve. While that worked, GM engineers decided to substitute the TV cable, which would indicate both throttle position and load. I think where you have slid into trouble is with the nonstock carburetors. The placement of the pickup point for the TV cable on the carburetor linkage is critical and this location changes with each vehicle application. Our suggestion would be to reference the original Q-jet carb TV-cable pickup point on the linkage. If you look at the original Q-jet throttle linkage, the TV cable connection will be located roughly 111/42 inches lower and slightly rearward from the centerline of the primary throttle shaft. You may have to make some kind of bracket that will place this same TV-cable connection point on your new Holley carb. Adjust the TV cable so that it is guitar-string-tight at wide-open throttle
If this doesn't help, it could be that the position of the throttle valve in the valvebody is incorrect. There are ways to check for the correct placement of the valve based on transmission pressure. The best way to do this is by getting help from a local transmission shop that has experience with these overdrive transmissions. The basic procedure will check the transmission line pressure at idle and how much the pressure changes as the cable is extended, as if the throttle was being opened while the engine was running. The key is to add just enough line pressure to increase the shift rpm based on engine speed and load. As you can imagine, this is a real can of worms. If you'd like additional tech help, Art Carr's California Performance Transmission should be able to help you out. It specializes in the 200-4R. CPT's Web site also has some technical data on positioning the TV-cable pickup on the throttle linkage and also diagnostic information that you should read and follow first to see if this will solve your problem. CPT also sells linkage adapter kits that will properly position the pickup point on your Holley carb if you don't want to make the bracket. For a Holley, it's PN 15999 for $37.99. CPT makes similar brackets for Dominators, Q-jets, and the Edelbrock carburetor.
It's much more of a hassle to replace the 200-4R with a 700-R4, and you will still be dealing with tuning the TV cable, so our recommendation is to get your existing trans dialed in and you'll be much happier. There are also several parts available for the 200-4R that both strengthen and increase its durability.
More Info
Art Carr's California Performance Transmission; Huntington Beach, CA; 800/278-2277; cpttransmission.com