My Dream Project: New Transmission and Maintenance Sled

I am getting a lot more people watching my blog and some of them are not gear heads so I am going to try and explain how things work on each of my updates to try to help the people who don't understand the inner workings of a 5 second drag racing car. I will try to explain things as simply as I can.

I received my new torque converter drive yesterday. I mounted the transmission to it and put it in the car so I could start building the mounts and frame crossmember.

The transmission is basically broken down into three distinct sections. They are the torque convertor, the converter drive, and the transmission, The first section is the torque converter which provides a method of transferring the engine's rotation to the converter drive input shaft. It is bolted to the engine's flywheel and rotates at engine speed.

The converter drive is a device that provides the motivating force for the transmission. This is done by pumping fluid into the torque converter as the engine spins the converter. Inside the converter are vanes or fins the are welded inside the converter housing and a drive turbine (that freewheels inside the torque converter) that turns the converter drive input shaft. As oil is pumped into the converter by the converter drive, it is forced to swirl around inside the converter. The swirling fluid impacts the turbine and causes it to spin. The higher the speed, the more pressure that is exerted on the turbine, the faster it spins, which in turn spins the converter drive input shaft. The converter drive then transfers that rotation to the transmission input shaft and turns the transmission gears.

The new converter drive is the latest technology and has what is called a lockup converter. Normal torque converters slip a little and waste horsepower and generate lots of heat! With a lockup converter, I can program it to lockup in one or more places during the run to minimize slippage. This is possible because the torque converter has a set of clutches inside that are squeezed together by hydraulic pressure. When they are squeezed together it locks the transmission shaft to the engine crankshaft and drives it at engine speed. This can be done after every shift to allow the car to experience a soft shift without causing the tires to spin and then lock up as the car's momentum increases. The lockups can be triggered by engine RPM, time, or a combination of the two. Prior to having lockup converters, transmissions could easily have 5% or more slippage.

The transmission that I am using is a manual planetary type transmission that is capable of handling lots of horsepower. A planetary transmission works by having an outer hub with gear teeth machined inside the hub. There is also an output shaft that has gear teeth machined on the outer diameter of it. There is a void between the gear teeth of the hub and the shaft. This void is filled with a cluster of smaller planetary gears that connect the outer hub to the inner shaft. When one side is spun by the engine, the other side spins at a reduced rate because the planetary gears roll inside between the inner and outer gears and reduce the number of revolutions of the output shaft. The gear sets have a clutch pack installed that allow the outer hub to lock to the inner shaft and create a 1 to 1 ratio of that gear set. This clutch pack is controlled by applying air pressure to a piston that squeezes the clutch pack together. This is what happens when a shift occurs. As many gear sets as needed can be stacked together to create a 2, 3, 4, or 5 speed transmission. Mine is a 3 speed transmission.

The shifts can be controlled by manually diverting air pressure to the gear set clutch packs or by using electric air solenoids that are controlled by the ignition controller or another type of controller.

Because this is a very sophisticated setup and will be abused by a large amount of horsepower, it will have to be serviced regularly. Therefore, I decided to fabricate a sled type mount that would allow me to service the torque converter without having to drop the transmission out of the car. Traci and I will have to do the service with no help so I wanted to make it as easy as I can on it. We simply unbolt the transmission and just slide it back in the car to get it out of the way so we can work on the converter drive and torque converter.

You can see in the pictures that I fabricated two tracks for the sled to slide in. They are fabricated out of a piece of chrome moly tubing that I split to make two half pipes.

I then fabricated a sled that mounts to the transmission and sits down into the tracks. When I remove the transmission mounting bolts, I can simply slide the transmission backward until i have room to pull the converter drive.