Automatic overdrives have been around for several years now--just a little longer than people have been trying to retro-fit them into older trucks. In these days of rising gas prices, it makes more sense now than ever to add one to your truck's drivetrain. The problem is that not everyone understands the way in which these transmissions function compared to the Turbo 350 and Turbo 400--which isn't really surprising as a lot of transmission shops still don't give the TV cable system the respect it deserves.
Chances are good that everyone reading this has either done it or knows someone that has installed a 700R4 or 200R4 into an older car or truck and has not been happy with the way it shifts. The most common complaints are that it shifts too hard, shifts too late, or won't downshift more than one gear. In a lot of cases, they were told to back the cable off to soften the shift, but then they would lose the multiple-gear downshift and cause the trans' pressures to drop--resulting in shortened trans life.
All these problems are the result of the TV cable not being set up properly. We cannot stress enough the importance of the relationship between the carburetor and the TV cable. Just simply bolting on a bracket that holds the cable is not enough.
Steve Holmes at Bow Tie Overdrives has spent a lot of time researching and developing a system to make it as easy as possible. The new TV Made EZ system is in its third incarnation and is about as easy as it can get. We took a trip out to Hesperia and had Steve walk us through an install on an intake system he had laying around. Stay tuned for more info on these GM overdrives next month as we explore some of the myths and misconceptions regarding their uses and installations.
The next piece to be installed was the back plate section of the linkage adapter. It should fit precisely around the linkage, and in order to get it in place, it must be tipped slightly at the top as it is placed in from the backside of the linkage. | 
The front faceplate of the linkage adapter was positioned over the linkage as shown. When correctly positioned, this faceplate will index over the extruded (raised area) hole on the linkage. | 
Once it was indexed over the extruded hole, Steve lined up the four bolt holes with the back plate section and secured it with the three small stainless steel panhead 6-32 screws and a 5/64-inch Allen wrench supplied in the kit--leaving the top bolt hole. After the vehicle is test driven and everything checks out okay, Steve recommends removing these screws one at a time and reinstalling them with a small amount of Loctite 242 (or similar product) to prevent them from vibrating loose. |
The cam, the piece that the TV cable actually rides in, was installed next. The cam has two pins that protrude from the backside, which must be indexed into the front faceplate. Once the cam was indexed correctly, the 8/32-inch cap screw was installed and tightened using the provided Allen wrench. | 
A factory TV cable was snapped into the carburetor plate and with a little slack on the cable end, Steve was able to easily connect the cable to the carb linkage. The cam has a groove machined into the lower edge that allows the cable to ride smoothly. | 
To set the TV cable length, simply push the lock to one side; fully open the throttle which will adjust the cable out and then close the throttle; and push the TV cable lock back--which secures the cable. |
Here's where the beauty of the system really comes out. By loosening the cam's attachment screw, you can rotate the cam within its arc and adjust the way the transmission shifts--smooth and early to firm and late--while still retaining the full movement of the transmission's throttle valve. | 
Steve also wanted to point out that not all TV cables are created equal. He recommends a factory one, or if you want braided steel, he offers one that has a spiral steel core (similar to a speedo cable). He doesn't recommend ones with nylon cores that are wrapped with braided steel because the engine heat will soften them enough to allow them to give slightly--resulting in a change in the amount of travel of the TV cable, thus changing the shift points and transmission pressures. | 
If you're using a used transmission, it's a very good idea to pull the valve body and remove the throttle valve assembly, and replace the springs and control valve with new ones from TransGo. Over time, the springs become weak and will not fully return the plunger to the closed position, which will result in higher trans pressures and harder shifts. |
Steve highly recommends installing a 0-300-psi pressure gauge in order to perform a pressure test of the transmission. The pressure gauge must be attached to the direct pump pressure port on the driver side of the transmission (above the manual shifter shaft approximately 3 1/2 inches). | 
Once the TV cable is adjusted correctly, you will need to bring the engine up to operating temperature, and then check the following pressure readings: pressure at idle with TV connected, pressure at idle with TV disconnected, and pressure at high idle with a full pull on TV cable. Bowtie Overdrives will provide you with the specifics of each test and walk you through them. If everything is working as it should, there will be an immediate pressure change with the slightest movement of the cable right off idle. | 
If you're dead set against checking the trans with a pressure gauge, you can get it close by pulling the trans pan and confirming that the plunger is fully seated at closed throttle, as pictured here. There should be six indented rings visible, and the push rod arm should be touching it. The plunger should start to move at the slightest pull of the cable. |
At wide-open throttle (engine off), the plunger should be fully depressed as shown here. | | |