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700R4 - TH-2004R - TH-350 - 4L80E - High Performance Transmission Products

Welcome to the Frequently Asked Questions (FAQ page). 
Below, we have tried to answer the most common questions visitors
may have.
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Transmission Gear Ratios

This information should only be used as a guide. Other variations in Transmission dimensions and ratios may be possible.

Popular Automotive Math Formulas and Conversions

RPM = mph X gear ratio X 336 divided by tire diameter.

To convert from:

Miles to Kilometers, Multiply by 1.609344
Liters to Cubic Inches, Multiply by 61.023744
Inches to Millimeters, Multiply by 54.4
millimeters to Inches, Multiply by .0393701

No, the 700R4 and 2004R only need voltage to control the torque converter clutch solenoid, all the shifts are performed hydraulically. We wire our transmissions up internally so all you need to do is attach a 12 volt source to the supplied pigtail and the trans will do the rest.

What is “Lock-Up”?

The term “Lock-Up” refers to a clutch inside the torque converter that , when applied, locks the internal components of the converter together to achieve zero slippage in the converter. These type converters are found almost exclusively in overdrive transmissions but were also incorporated into some 3speed automatics with electronic control.

Why do I need a “Lock-Up” torque converter?

The greatest source of heat in an automatic transmission is the torque converter. This is because there is a constant source of friction within a converter and as we know, friction creates heat. Even the most efficient low stall torque converter will never stop slipping so you will always have that source of heat generation in a non locking converter. When you add stall speed to a converter you are raising the RPM that the converter must attain before it transmits full engine power back to the transmission. While this is great for performance, it creates an even greater heat and efficiency 
problem. To make matters worse, in an overdrive transmission, even with steep gears, the engine rpm’s at cruise may be substantially less than the stall speed of the converter, a recipe for disaster. By applying a Converter Clutch you eliminate this slippage and heat source, allowing you to have the benefits of a performance oriented stall speed, plus economy, efficiency and lower operating temperature.

What do you mean by stall speed?

Think of a torque converter as two fans facing each other. The first fan is attached to the engine and as it spins moves air to the second fan which causes it to spin as well. This second fan is attached to the transmission. As the speed of the first fan increases it pushes greater amounts of air to the point where the second fan is turning at nearly the same speed. This would be considered stall speed. In the torque converter these “fans “ are moving oil instead of air and by manipulating the angle of the fins, size of the converter and internal oil flow we can alter the speed at which the converter passes engine speed back to the transmission.

There are a couple of ways converter stall speed is rated, “brake stall” and “flash stall”. Naturally a converter slips the most at idle by design, so when you are stopped at a light it doesn’t drag the engine down like releasing a standard clutch. When the light changes and you ease on the throttle the converter begins passing engine torque to the vehicle gradually as rpm increases giving you a smooth ramp up to acceleration. This holds true for both stock and modified torque converters. If you were to hold the brake on and apply throttle till the engine stopped making rpm this would be “brake stall” speed. This is hard to measure because most performance vehicles will overpower the brakes and begin spinning the wheels before the stall point is reached. If you were to observe
the tachometer as you made a full throttle launch with little or no wheel slip the tach would swing up quickly then stop and rise more slowly as the car accelerated down the track. The point to which the tach would quickly swing to would be the “flash stall” speed. You can also measure flash stall by having your transmission in top gear with the kickdown linkage disconnected and floorboarding the throttle, at approximately 45 mph. this will indicate flash stall as well.

There are a great many variables used in rating a converters stall speed including, cam size, engine torque, vehicle weight and gearing to name a few. An 1800lb. t-bucket with a mild small block can use the exact same converter to achieve 2000rpm stall speed as a 3800lb. Chevelle with a warmed up big block would use to obtain a 3000 rpm stall speed. The difference is in the torque converters ability to transfer engine power back to the trans. A heavier vehicle with more torque will need a higher rpm to achieve this transfer. That is why it is important that your converter builder have as much information as possible about your engine and vehicle combination so that he may design a converter to best get the power your engine makes transferred to the trans and rear wheels in the most efficient way possible.

What is COMPUSHIFT?®

COMPUSHIFT® is a revolutionary, state of the art product designed by HGM Automotive Electronics Inc. The COMPUSHIFT Transmission Control System (TCS) operates automatic  shifting and converter clutch lock up for the 4L80E, 4L60E, AODE and 4R70W transmissions. COMPUSHIFT® is fully programmable and user friendly. Adding an electronically controlled transmission into a street rod, truck, RV or vehicle was never so easy.

The Skinny on TV cable Adjustment

First a bit of history, the Throttle Valve  or TV system for transmission pressure control has been around since GM introduced the Hydramatic transmission before World War II nearly 70 years ago. These early systems used a collection of rods and clevises to connect the accelerator linkage to the transmission and required skill, and patience to adjust as well as some special tools. GM continued to use this type of system as did both Ford and Chrysler until the 1970’s when a cable system was adopted. The more “modern” variants of this system have been in place since the 1976 introduction of the TH-200 transmission. Mercifully, GM did away with the complex linkage and provided us with a simple cable system which stayed in use till 1993 when the General phased out tv controls all together for fully computerized transmissions. 

Understanding TV operation:  

  Basically, the TV system provides the transmission with pressure increase proportionate to throttle opening. Why is this important you ask? Well, when you are cruising around slowly or gently accelerating you want the transmission to shift smoothly and keep the engine at a practical and efficient rpm. But, when you want to accelerate quickly you want the transmission to keep the engine in a higher rpm range where it makes more power. Under this scenario the transmission needs increased pressure to apply the bands and clutches and keep them from slipping under the demands of increased power and acceleration. A modern TV system uses a cable which runs from the accelerator linkage to an internal transmission linkage that depresses a plunger in the valve body to regulate tv pressure so that transmission line pressure matches acceleration demand. 

Cable setting basics: 

All GM transmission requiring a tv cable use the same basic range of adjustment. From idle to wide open throttle , about 1 1/8 inches of cable are pulled, and at wide open throttle the cable is as tight as it can be without limiting throttle travel. The cable is pulled in a straight line from idle to wide open throttle to correctly keep transmission line pressure rise in harmony with throttle opening insuring accurate shift points, shift firmness and kickdown response. No matter what kind of cable system you are using, you should always verify that you have the correct range of throttle cable travel and that it is as tight as it can be at wide open throttle. If you have these two parameters in place then you will have successfully adjusted your cable and your transmission will operate as designed.

 Due to the very wide variety of carburetor and fuel injection systems it is impossible to design a cable that will work with every model and application. However, if you follow the principles set forth in the previous paragraph then it is possible to simply and correctly adjust a tv cable for any application. If you are using a Chevrolet style Quadra jet these have the ideal ratio already designed into the linkage. In fact, nearly any Chevy carb used on a small block application from the late 60’s on up to the late 80’s will have the correct linkage. In these instances, you can use the factory style tv cable and bracketry to install and adjust your cable. These brackets may have been bolted to either the intake or the carb flange and routed the tv cable in a straight line with the attaching point at the carb linkage. If the factory style linkage cannot be located, Holley sells a nice replacement bracket under part number 20-95 that not only holds a factory style tv cable but also most GM throttle cables as well. For those with a Holley, Barry Grant or AFB style carb from Edelbrock or Carter, things get a little trickier since these do not have the proper geometry for proper tv cable operation and may pull out too much or not enough cable and at the wrong rate.

Phoenix Transmission Products of Weatherford Texas, has developed individual brackets to correct these tv problems on these carbs, allowing simple and precise adjustment without special tools or gauges just as in a factory installed application. These levers simply bolt on to the carb linkage with supplied hardware and give perfect TV geometry to aftermarket carburetors not designed for tv control systems. The levers can be used with stock style tv cables or aftermarket cables such as those made by Lokar or others. The important thing to remember is to keep the cable running in a straight line with the cables attaching point at the carb linkage for best results.

 In the event that you have some other type of carb or injection that does not have a provision for a tv cable, fear not. The simple rules for cable travel and adjustment still apply. You may need to get creative but you can still achieve perfect tv geometry with any setup. Find a place on your linkage system that has the correct amount of travel, which is about 1 1/8 inches, then make a secure mount for the tv cable and make your adjustment. You can even run a Lokar style cable back through the firewall and connect it to the accelerator linkage inside the vehicle as GM did on some of it’s models in the 1960’s and 70’s. This also is a discreet way to hide the fact that you are running an overdrive transmission on an otherwise stock appearing restoration.

 Regardless of the fuel system you chose, you will always get the desired results if you have the correct amount of travel and the cable is as tight as it can be at wide open throttle. It is just that simple.

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