The Story Behind The Breakthrough TCI Constant Pressure Valve Body That Removes The Fear From Automatic Transmission TV Cable Adjustment
Let’s face it: Even the most hardcore car guys often admit to avoiding anything to do with automatic transmissions. That’s because they can be frustrating, and when not installed right, the automatic transmission can turn your hot ride into a big piece of metallic frustration. Properly installing an automatic isn’t too difficult but getting it properly adjusted can be. The throttle valve (TV) cable controls both the line pressure inside the transmission and the shift points, and it must be correctly adjusted the first time it’s installed. If it isn’t adjusted correctly, the transmission might shift gears without adequate line pressure, which will burn up the clutches inside the transmission within a few 100 miles.
TCI Automotive, however, says it has removed that headache from the equation with its new Constant Pressure Valve Body. For more information on exactly what that means we spent a little time with TCI Product Manager Stanley Poff. Here’s what he had to say about how TCI made working with an automatic transmission a whole lot easier:
Q: First of all, what does the valve body in an automatic transmission do? A: The valve body is like the brains of the transmission. It tells the transmission what gear to go into by controlling the fluid line pressure. But traditionally, in order for the valve body to work properly, it must work as part of a team with the governor, the TV cable and the vacuum of the engine. If the valve body and governor aren’t working correctly with the given amount of engine vacuum, then you will have shift problems.
Q: Why is a valve body that provides constant pressure a good thing? A: Traditional throttle bodies depend on the TV cable to control the amount of pressure and when to shift. As you depress the accelerator pedal, the TV cable is extended and pressure inside the transmission rises from approximately 80 to 90 psi to 200 to 230 psi at full throttle.
When people install an automatic transmission in their car, or install an engine in their car, and have to hook up the TV cable, it can be difficult adjusting the TV cable correctly. Several different things cause this. The biggest problem is that the TV cable from the factory is designed to work with the factory setup. If you change anything with the throttle, it can change the setup. For example, say you are switching out the factory carburetor for a higher performance carb as part of an engine upgrade. It can be a Holley, or a Barry Grant, an Edelbrock or a number of other options. Those carbs weren’t designed to work with every TV cable system. Those manufacturers had to make a bracket to mount the cable and a connector to go wherever you are hooking it to. And while they can get it close, those manufacturers cannot guarantee it’s going to be perfect because they don’t know what the rest of your car is like. So the more things you have going on like that, the more compounded the problem becomes, making it even more difficult to adjust the TV cable properly.
All kinds of companies are attacking this problem by developing different kinds of TV cable systems. But what we decided to do is eliminate the TV cable, as far as controlling pressure is concerned. That’s why we developed the Constant Pressure Valve Body. It maintains a constant 200 psi as soon as you crack open the throttle. In other words, at idle the pressure might be 100 to 120 psi, but as soon as you touch the throttle it goes to 200 psi. Now when the transmission shifts, it will always have plenty of pressure to make a good, firm shift. Before, if the TV cable wasn’t hooked up properly, the transmission would try to shift with too little line pressure which burned up the clutches. This isn’t a concern with the Constant Pressure Valve Body.
Q: Then is the TV cable necessary at all? A: Yes, it is still used to control your shift points. A perfect example happened recently when a magazine writer we were working with installed a Constant Pressure Valve Body in a project he was doing. When he finished the project, he hooked the TV cable to the carburetor but forgot to hook it back up to the transmission. He drove with it like that for 600 miles before figuring out the problem. Because the TV cable wasn’t hooked up, it was shifting way too early, but the Constant Pressure Valve Body was preventing the transmission from getting torn up. So once he hooked the TV cable to the transmission, everything was fine. If that had happened without the Constant Pressure Valve Body, he would have ruined that transmission in way less than 600 miles.
Q: Why 200 psi? A: The actual pressure number isn’t critical. Having enough pressure to get the transmission to make good, firm shifts is more important. We could have gone with 250 psi, or even 300, but our engineers felt that 200 psi was plenty to get the job done right. We didn’t want to have the pressure so high that it knocked the dash out every time the transmission shifted gears. There is no reason to go overboard with it.
We are trying to make the transmission foolproof. The Constant Pressure Valve Body acts as a failsafe. This protects the customer if he doesn’t get the TV cable hooked up properly, or just plain forgets, then this valve body is going to protect him until he gets everything adjusted the right way.
Q: What will the Constant Pressure Valve Body work with? A: The original TCI Constant Pressure Valve Body was designed to work with the GM 700R4 transmissions produced from 1982 through 1986. Recently TCI released a new Constant Pressure Valve Body that works with the 1987 through 1992 700R4 transmissions as well as for Ford AOD transmissions produced from 1980 through 1993. Last is the GM 2004R transmission, which gives us the lion’s share of the automatic transmission market. We believe the Constant Pressure Valve Body is pretty revolutionary, and it has allowed us to rethink the way we do transmissions. We will probably carry this through to all the transmissions we develop in the future. Right now all of our Street- Fighter and Super StreetFighter Transmissions will have Constant Pressure Valve Bodies in them. We’ve raised the bar and our competitors aren’t going to like it, but it is easy to see how this technology will be beneficial to the end user.
Q: How hard is it to install? A: Installing a Constant Pressure Valve Body isn’t really difficult at all. It is probably a two to three-hour operation if you take your time and do it right. You’ve got to drain the transmission fluid, drop the pan, unbolt the valve body, bolt the new one up along with new screens, and that type of thing, and then reinstall the pan and add new fluid. Installing it isn’t a big deal. You can do it in your driveway with a set of jack stands and general hand tools. It’s just a matter of ordering up the right valve body and getting down to business.
Q: If I don’t change anything else, will the Constant Pressure Valve Body benefit me? A: You mean, assuming you already have the TV cable properly adjusted? Yes, it will still benefit you. The Constant Pressure Valve Body is like our other valve modification kits. It creates a firmer shift and a quicker shift. Those will equal better performance. There isn’t a delay between shifts with this valve body; it is almost immediate. With this valve body, we’ve taken some of the technology from our previous performance valve bodies and incorporated that as well. So it definitely improves performance over stock.
Q: When installing the Constant Pressure Valve Body in an otherwise stock transmission, are other upgrades required? Will the higher line pressures create heat and require a trans cooler?
A: No, the Constant Pressure Valve Body does not require anything else. In fact, it might lower your transmission temperatures because the higher pressures keep things locked up. Since there is no slippage between the clutch packs, both temperature and wear should be reduced. Still, it is always a good idea to run a transmission oil cooler in any automatic transmission application. It helps durability. Also, since you will have to add automatic transmission fluid, it is a good time to make sure you are using good fluid. I like our oils and use them in all my vehicles. We have a mineral-based Max Shift oil that’s good for the street and racing. We also have synthetic oil that has a lot of proprietary additives that really increase both performance and longevity.
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