Basic Auto Mechanics – Week 9 Automatic Transmissions

This is it, the final class in the East Brunswick Vo Tech Basic Auto Mechanics course.  This last class was all about automatic transmissions.  We discussed the basic parts of the automatic transmission and what they do.  This was a very basic level introduction to automatic transmissions, the teacher told us he could probably teach every one of us in the room how to rebuild it, but it would take 6 months of working on it every day!

We started by talking about the torque converter.  It was explained to us that there is oil inside of the torque converter which gets pushed to the outside of the converter and starts the transmission moving.  I believe that it acts a lot like a clutch and pressure plate on a manual transmission, but for an automatic.  We were also shown how it connects to three different contact points, two spline connections, and one notch connection.  A common mistake for newbie’s is that they get 2 of the connections in and it looks good, but when they go to put the transmission on the motor, it doesn’t quite go on and they use the transmission bolts to pull the unit onto the motor.  This in turn sandwiches the torque converter to the flywheel and crushes it destroying the transmission.  When you put the transmission in place, it should sit flush with the mounting points for the motor without having to use the bolts to pull it in.  We were also shown how they have threaded bolts on the end of the torque converter which get put into the flywheel and tightened through the space in the bottom of the transmission.

We were then told about common leaks in the transmission.  It is common for the transmission to leak from the pan after it has been serviced.  This is usually caused by someone tightening up the pan bolts too tight and warping the pan.  The bolts that hold it in actually dimple the hole that they go through and misshapen it.  When the pan is not flat, the gasket cannot seal it properly.

Another common leakage point is the rear seal.  Replacement is fairly straight forward; you punch it out with a punch and put the new one in.  The teacher warned us about the yoke being wobbly, if you can move the driveshaft yoke at the back of the transmission up and down or back and forth, the bushing that is in the back half of the transmission could possibly be bad.  This can be replaced by using a punch slid down into one of the grooves in the side and deforming the bushing until it comes out.  To put the new one in, freeze it and it will slide right in.

If the front of the transmission is leaking, there is a seal on the shaft where the torque converter rides that has a seal on it.  It is common for this seal to wear down the metal that it is riding on and therefore allow fluid to pass by it.  When this happens, you can install the new seal an 1/8 inch forward or back on the shaft to stop the leak.  This is not the proper way to fix it, but it will work.

We then went over some more parts of the transmission.  We took the pan off a sample transmission and we were shown the gear selector mechanism.  This was connected to a spool valve which dictates where fluid is allowed to flow throughout the transmission.  This allows the proper gear selected to be engaged in the transmission.

It was shown where the fluid lines leave the transmission and go up to the radiator for cooling.  There is a whole section of the radiator that is dedicated to the transmission fluid and the proper cooling of it.

He told us about the recommended way to drop the transmission pan.  He recommends having a large catch pan placed underneath the pan since it will be messy.  To eliminate the large mess that will happen, you should remove every other bolt from the transmission.  Then you should take out all the bolts except for the four corners.  At this point, you will want to loosen the bolts slightly and lower the back part of the pan, at this point the fluid will be pouring out.  Let the pan drain.  Then you can hold the pan up with one hand and take out the remaining bolts with the other.  Once the bolts are removed, you can gently lower the pan; which still has fluid in it, and drain some of it out to lighten it.  You don’t want to just dump it out because you will want to look at the fluid to see if there is anything wrong with the transmission.

I learned a lot in this last class because I have not had to deal with automatic transmissions very often.  They are completely foreign to me and almost all of the information was new.  It was very informative and good to see.

This was the last class of the 9 week Basic Auto Mechanics Course, I received a certificate that stated I had completed the 27 hours of training.  It was printed on a piece of colored paper and looks pretty cheesy, but it does state that the training was complete and I guess that is what is important.



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