i am wondering how old school tranys work. i kinda get how the new modern tranys work but i do not get though. could some one explain or show some pictures on what makes them work.

Thanks Ryan

 

You need to aquire a colored flow chart. It would take more than 10 years to explain how an auto trans works.

 

where would i find such a thing??

 

They are normally in the front of the GM training manuals, and often come up on e-bay. You can google Transtar as well. They may be able to sell you one.

 

I think I can give you a basic idea of how they work.

First think of how a manual camera works. The lens opening allows a volume of light onto the lens and is adjustable from a tiny opening to a large opening. The camera's shutter is a timing device that measures how long light is allowed in.

Light is measured by the lens opening and timed by the shutter.

The valve body inside an older automatic trans uses spring tension to control spool movement, which controls hydraulic fluid direction. Accumulation is also part of timing. Inside the valve body are channels. Some channels lead to accumulation areas that are for nothing but filling up to lengthen shift timing.

Depending on which spool you are dealing with. You have what's called a pilot pressure pushing one end of the spool and a spring on the other preventing it from moving. As pressure builds, pilot pressure overcomes the spring and the spool moves and fluid is redirected.

Several things are involved that affect clutch holding force and shift time.

To make the front pump produce more line pressure for clutch-pack holding power. There is a pressure releif valve on the pump. Adding a stiffer spring or shims increases the pumps output pressure.

Sepperator plates between the upper and lower valve body has holes in it to control fluid volume and direction, like accumulators. Holes can be plugged or drilled larger depending on what they control. You can make a log splitter from an automatic transmission if you know what you are doing. The aftermarket is the best place to turn when playing with sepparator plates. There are many ways to acheive the same outcome. Typical aftermarket shift kits come with their randition of sepperator plates. Usually they reduce or eliminate accumulation to shorten clamping force on the clutch packs. Then they give you a few springs to put behind some spools in the valve body to adjust shift timing.

The length of time it takes for clutch packs engauge varys with a variety of outside influences. Engine torque, tire diameter, gear ratio, vehicle weight, size of carburetor all affect how a transmission will shift. Rarely will you hear an automatic transmission shift correctly. If it shifts too quickly, it will sound like something bumping the floor pan under the car. To long of a shift will generate heat and cook the transmission. A perfect shift will just haze the tires accelerating hard. A bad shift will drag the engine out of it's torque range and sound labored.

It does take years to understand what works and what doesn't. Reading a hydraulics schematic or understanding the symbols takes a long time. Most people cannot read hydraulic schematics so don't worry about it. I hope my exlpanation helped you understand a little. Let me know. I can drop down a level or two and am open to critisizm.

 

helped make seance of some Schematics for the TH400 i have.

Thanks for taking the time to write this

Ryan

 

That's what breaks at work are for

 

lol