70 psi x 1 sq. in. = 70 lbs of force 70 psi x 9 sq. in. = 630 lbs of force. Figure 1 Figure 2

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BASIC HYDRAULICS What is Pressure? In hydraulics, it can be defined as force applied uniformly over a contained area and is measured in force per unit of area. by Larry Frash 70 psi x 1 sq. in. = 70 lbs of force 70 psi x 9 sq.

In this edition we ll cover how this pressure is used and the difference between pressure and force.

It s important because with this information, you can calculate line pressure, accumulator pressure, shift timing, clamping force of a particular clutch pack or band servo and a lot more.

The most common way in our industry to measure hydraulic pressure is in PSI (pounds per square inch).

1 BASIC HYDRAULICS What is Pressure? In hydraulics, it can be defined as force applied uniformly over a contained area and is measured in force per unit of area. by Larry Frash 70 psi x 1 sq. in. = 70 lbs of force 70 psi x 9 sq. in. = 630 lbs of force Figure 1 Figure 2 In the past editions of Basic Hydraulics, we ve covered how various types of pumps function and how the pressure is regulated. In this edition we ll cover how this pressure is used and the difference between pressure and force. We ll also show you how to calculate the amount of force, as long as you know the pressure and what the area is that this pressure is being applied to. But why is this important? It s important because with this information, you can calculate line pressure, accumulator pressure, shift timing, clamping force of a particular clutch pack or band servo and a lot more. What is pressure? In hydraulics, it can be defined as force applied uniformly over a contained area and is measured in force per unit of area. The most common way in our industry to measure hydraulic pressure is in PSI (pounds per square inch). If pressure is contained in an area like in a clutch drum, pressure is equal anywhere in that area that you measure it. Sound confusing? Lets look at some examples of areas first. Figure one illustrates a scale with a 1sq. in. apply surface. If you were to apply 70 psi of pressure to the surface, there would be 70 lbs of force on the scale. If you were to apply 100 psi to the surface there would be 100 lbs of force on the scale. If you were to increase the apply area to 9 sq in, and applied 70 psi of pressure to this larger area, you would have 630 lbs of force to the scale (figure 2). This is because at 70 psi there is 70 pounds of force applied to each of the 9 square inch (70 x 9 = 630). That part is fairly simple to understand. But how many square apply areas do you see in a transmission? The trickiest part about calculating apply areas is that the parts are always round! There are two different calculations that can be used to calculate the area of a circle. One is the traditional and most accurate also very difficult to use. And the other is much easier to use but a little less accurate. The difference in the accuracy is so small however that it really makes no measurable difference. πr² = The Area of a Circle This is the traditional calculation. The r symbolizes radius which is half of the diameter. The π symbolizes pi which is the circumference of a one inch diameter circle. So to use this formula to calculate the area of a circle, you first you have to divide the diameter by 2 then multiply that by 14 GEARS March 2006

70 psi x 12.57 sq. in. = 879.9 lbs of force Figure 3 Figure 4 itself. Then, multiply that number by pi (3.14159265).

One more thing to point out is that pi never ends, it has to be rounded off. DxDx0.

To use this formula to calculate the area of a circle all you have to do is multiply the diameter x diameter x 0.7854. To calculate a 4 inch circle, the equation would look like this, 4 x 4 x 0.

2 70 psi x sq. in. = lbs of force Figure 3 Figure 4 itself. Then, multiply that number by pi ( ). So to calculate the area of a 4 inch circle (figure 3), the equation would look something like this. 2x 2x = One more thing to point out is that pi never ends, it has to be rounded off. DxDx = The area of a circle This calculation is much more simple and is accurate enough for any calculations we would do in our industry. To use this formula to calculate the area of a circle all you have to do is multiply the diameter x diameter x To calculate a 4 inch circle, the equation would look like this, 4 x 4 x = If you compare this answer to the traditional way, you ll see that it is very close; especially when you consider rounding the number to the 100 th decimal. The answer from both of these equations would both equal sq in. Insta-Clean quality that can t be beat! Now at a price that can t be beat! IC-4, 2-H.P. IC-7, 3-H.P. IC-10, 5-H.P.* $2, $3, $4, No other Parts Washer on the market has the Quality, Features, Horsepower, and Warranty offered at these prices! * IC-10, 3-Phase Electric Heat Prices are for continental US F.O.B. AZ. Prices are subject to change without notice. The industry's first, ever, completely reprogrammable handheld ransmission controller for the later multi-stage solenoid sequencing units is almost here. The new Schaffer Programmable Controller will not replace the Schaffer Shifter, it will be programmed for units that the Schaffer Shifter cannot control. Features include: 12 individually controlled negative outputs 12 individually controlled positive outputs Eight switch indicator lights Keep your eyes open for the new programmable controller to be released in April 2006! GEARS March

What is Pressure? 6 x 6 x 0.7854 = 28.27 sq. in. 2 x 2 x 0.7854 = 3.14 sq. in. working area = 25.13 sq. in. Figure 5 Figure 6 6 x 6 x 0.7854 = 28.27 sq. in. 4 x 4 x 0.7854 = 12.57 sq. in. working area = 15.

To calculate the working or used areas (light blue), you must again subtract the unused area from the total area. See examples (figure 7 & 8).

The key is that you first have to calculate the area of the unused area and subtract it from the total area of the piston. Notice I said the word area.

3 What is Pressure? 6 x 6 x = sq. in. 2 x 2 x = 3.14 sq. in. working area = sq. in. Figure 5 Figure 6 6 x 6 x = sq. in. 4 x 4 x = sq. in. working area = sq. in. 4 x 4 x = sq. in. 2 x 2 x = 3.14 sq. in. working area = 9.43 sq. in. Figure 7 Figure 8 There are two separate apply areas that are used. To calculate the working or used areas (light blue), you must again subtract the unused area from the total area. See examples (figure 7 & 8). If you were to put this 4 diameter piston on the scale with 70 psi pressure added to it, the force would be lbs (figure 4). But what about pistons that have a hole in the center. The key is that you first have to calculate the area of the unused area and subtract it from the total area of the piston. Notice I said the word area. That s because if you subtracted the diameters instead of the areas, the math won t work. The piston in figure 5 has a total diameter of 6 inches which calculates to a total area of sq. in. (6 x 6 x ). The unused portion of this piston has a diameter of 2 inches which calculates to an area of 3.14 sq in (2 x 2 x ). When you subtract the unused area from the total area, the used area equals sq in ( ). If you put this piston on the scale at 70 psi, the apply force would equal to lbs (figure 6). Enough to lift a small car! Imagine the force on this piston if the mainline pressure exceeded 300 psi. Well, don t imagine just do the math. Now let s look at a dual area piston. This piston is similar to one you would find in a 4L80E direct clutch drum. There are two separate apply areas that are used. To calculate the working or used areas (light blue), you must again subtract the unused area from the total area. See examples (figure 7 & 8). The large outer area would have a working area of sq in. The small inner area 16 GEARS March 2006

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5 What is Pressure? Total apply area = 3.14 sq. in. Total area of the 4'' servo = sq. in. Unused area = 3.14 sq. in. Total apply area = 9.43 sq. in. Figure 9 Figure 10 Total area of the 4'' servo = sq. in. Pin area = sq. in. Total release area = sq. in. Figure 11 Servos are a little different to calculate but you still subtract the unused area from the total area. The servo in figure 9 is similar to a C-6 in that it uses the inner area of the servo to apply the servo. would have a working are of 9.43 sq in. A 4L80E in reverse uses both apply areas in reverse so you would add these area together for a total apply area of sq in. At 280 psi line pressure, the direct clutch in this example would have lbs of apply force! Servos are a little different to calculate but you still subtract the unused area from the total area. The servo in figure 9 is similar to a C-6 in that it uses the inner area of the servo to apply the servo. The servo in this example has an apply diameter of 2 inches which calculates to an apply area of 3.14 sq in. The servo in figure 10 is similar to a 3T40 in that it uses the outer area to apply the servo. To calculate the apply area you would subtract the unused area from the total area. The servo in this example has a total area of sq in. So, when you subtract 3.14 sq in from the total area, the apply area would be 9.43 sq in. The difference between clutch pistons and servos is that most servos use pressure on the pin side to release the servo. To calculate the release force of a servo, you must subtract the area of the pin from the total area of the servo (figure 11). As you can see, there s a lot more about hydraulics than can be covered in one article. So we ll wait until the next edition of Basic Hydraulics to dig deeper and explain more ways to use hydraulics. 18 GEARS March 2006

Don t delay, shudder or slip The new Sonnax Bushing & Thrust Washer Kit for VW/Audi AG4 transmissions can save you hundreds in pump and drum replacement costs.

COrrection The Sonnax precision bushings and washers are designed to have tighter clearances for better drum stability and improved circuit integrity.

6 Don t delay, shudder or slip The new Sonnax Bushing & Thrust Washer Kit for VW/Audi AG4 transmissions can save you hundreds in pump and drum replacement costs. COMPLAINT SECONDARY COMPLAINTs Cause Worn bushings and poor sealing ring performance associated with excessive clutch drum run-out and instability. COrrection The Sonnax precision bushings and washers are designed to have tighter clearances for better drum stability and improved circuit integrity. Bushing & Thrust Washer Kit Delayed reverse, low line pressure in reverse Clutch failure Shudder or slip on shift Low clutch circuit pressure VW/AUDI AG4 Reverse Clutch Drum Bushing (K2) Shaft Bushing (K1) Pump Housing Bushing Pump Gear Bushing K 1 Forward Clutch Drum Bushing (K1) 1 Shaft Bushing (K1/096, 097, 098 only) 1 Reverse Clutch Drum Bushing (K2) 1 Pump Gear Bushing 1 Pump Housing Bushing 1 Thrust Washer OE thickness 1 Thrust Washer.015" thicker Thrust Washer,.015" thicker Forward Clutch Drum Bushing (K1) Thrust Washer, OE thickness Volkswagen and Audi units can exhibit a variety of problems when excessive clutch drum run-out and instability lead to worn bushings and poor sealing performance. Delayed reverse, low line pressure in reverse, clutch failure, shudder or slip on shift and low clutch circuit pressure are just a few of the potential symptoms. The Sonnax Bushing & Thrust Washer Kit contains five precision bushings and two thrust washers that boost sealing performance. The bushings are steel-backed and bronze-lined for better wear resistance, and tighter clearances that provide more drum stability and improved circuit integrity. Bushing installation requires no machining, and this kit works in AG4; 096, 097, 098, 01M, 01N and 01P units Sonnax D E S I G N E D T O S A V E TM Automatic Drive P.O. Box 440 Bellows Falls, VT USA F: info@sonnax.com See your nearest Transmission Specialties distributor & ask for Sonnax quality engineered products. VISIT OUR WEBSITE FOR SONNAX REAMERS & OTHER TOOLS

by David Skora These pressure readings are based on the computer reacting to the load conditions of the vehicle. Pressures may vary

by David Skora These pressure readings are based on the computer reacting to the load conditions of the vehicle. Pressures may vary Looking inside the Volkswagen 09G 6-Speed; Part 3 Looking inside the Volkswagen 09G 6-Speed; by David Skora PART 3 I n past issues we looked at the design and operation of the VW 6-speed transmission.