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Re: Understanding what is inside your Torque-Converter automatic gearbox
This is my first post in TeamBHP. I have been following this site from ages and always wanted to contribute. This post on Torque converter is possibly the best place to start from.
Writing this post based on my experience in selecting torque converter and designing of automatic and powershift transmissions for Off-highway vehicles.
To explain the principle: Imagine two fans facing each other, rotating one of the them will make the other one rotate but with a much slower speed. Now imagine the two fans inside a closed chamber, this would make the second fan (or driven fan) go turn a little faster. Now replace air in the chamber with oil and you have much better speed transfer from the driver fan to the driven fan, but with lot of loss in efficiency. The driver fan in the fluid coupling is called the pump and the driven fan is the turbine. Obviously, the pump and turbine are designed to have a good efficiency. This is the principle of fluid coupling and this sort of fluid coupling is used in small and low-cost forklifts.
Taking this fluid coupling further, there is a stator added between the pump and turbine. The pump draws the fluid from the center and throws it on the turbine near the circumference. The turbine reacts to this fluid at the circumference and allows the fluid to drain close to the center. The stator picks up this fluid from the turbine and redirects it towards the pump and increases the volume of fluid in the pump. As the volume increase, the force applied on the turbine increases hence you get the torque increase. Thus, the name "Torque converter". The increase in torque is highest at lower speed. This is the reason for the good pickup from the torque converter transmissions. As the speed of the turbine increases the torque multiplication reduces (as the turbulent flow in the coupling changes to laminar flow). These sort of torque converters are used in vehicles which do not travel in single direction for a longer duration and have frequent start and stops. For example: Backhoe Loaders, Wheel loaders.
With Torque converter couplings, you will not be able to achieve 100% efficiencies. And hence lower fuel efficiency. Taking this further, a lockup clutch is introduced into the system. This clutch mechanically locks the pump and turbine when the torque multiplication becomes closer to 1. With the lockup clutch, one can achieve ~100% efficiency. These torque converters with lockup are used in cars, trucks, and busses where customers are more concerned about the fuel efficiency.
I have worked on transmission where the torque multiplication is as high as 7 (thanks to the twin turbine design in torque converter). And, as low as 1.3 on city buses where the pickup is not so important.
Efficiently, the torque at the wheel (at startup) is the function of gear ratio and the torque multiplication from the converter.
1. Gland Nut
I have worked on 3 drive shafts for V8 and never messed with that nut. I I don't even agree with the FRM that it should be loosened. The only thing I would do is tighten it more if the existing play is too big, but have never seen that either. I took the drive shaft out in one piece (both halves hooked up), left it on the floor and took pictures of it with the marks as they were. I then examined the play and split the halves, cleaned the splines extremely well, replaced the bearing, bracket and dust boot (bellow), lubricate the splines with grease, then put it back together on the floor and compared with my initial pictures. When I was satisfied that everything was just as before, I installed it back on the car. Lubricate also the end bushings before installing it. When you take it out, you'll see which "end bushings" I am referring to.
Make sure when you tighten the two bolts of the bearing bracket that the bracket is in its free position. The FRM talks about that too.
2. Alignment
I too had the same issue on one car. just like you, I decided to put it back exactly in the same position because I had no vibrations before. In your case it is one (not two) teeth off.
3. Transmission Shifter Play
Yes, there should be a plastic bushing and almost no play (when a new one is installed). I recommend installing a new one "since you are there anyway" (actually aren't there two of them, one at each end?). They are very cheap, but I got to warn you: they are not easy to be installed. You may have to warm it up in hot water first. Buying an extra one in case you mess up the first in the installation process is also a good idea. I did mess up the first one.
Maybe other members have more to say.
Good Luck!
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