Servo

[HellOnWheels]

What is it about these "super" servos that makes one work so much better than another when they both have to fit into the case. One has more fluid holding capactity than the other?

TIA

HOW

 

[Firechicken]

The better one has a larger piston beneath the cover. A larger piston = larger surface area. Larger surface area = more force applied to the pin which engages the band. More force engaging band = faster shift with less slip and less heat. Faster shift, less slip and less heat = desirable.

 

[Marc87GN]

The better one has a larger piston beneath the cover. A larger piston = larger surface area. Larger surface area = more force applied to the pin which engages the band. More force engaging band = faster shift with less slip and less heat. Faster shift, less slip and less heat = desirable.

What he said. I actually have 4 pistons on my toolbox (1 is now in the car) and you can see the difference in sizes. I have a standard 200-4R piston, GN piston, Billet Servo & Case stretcher. The Case stretcher is the largest you can probably fit in the cover and in the bore. I finally started driving the car yesterday and with the higher stall, it's just a slight bump into the next gear. At 1/4 throttle or more, it's a very firm/quick 1-2 & 2-3 shift. I can't wait to try it at full throttle.

 

[Hacksaw]

Marc:

I just hope you don't break an input shaft or Forward Clutch drum shaft!
-Mike H.

 

[HellOnWheels]

What he said. I actually have 4 pistons on my toolbox (1 is now in the car) and you can see the difference in sizes. I have a standard 200-4R piston, GN piston, Billet Servo & Case stretcher. The Case stretcher is the largest you can probably fit in the cover and in the bore. I finally started driving the car yesterday and with the higher stall, it's just a slight bump into the next gear. At 1/4 throttle or more, it's a very firm/quick 1-2 & 2-3 shift. I can't wait to try it at full throttle.

If you look one of the assemblies over, it would be pretty easy to ENLARGE the FLUID capacity either between the cover and piston top as well as the piston's inside, would this get the same results as more surface area?

HOW

 

[Marc87GN]

Marc:

I just hope you don't break an input shaft or Forward Clutch drum shaft!
-Mike H.

That makes 2 of us. I'm driving it easy for the first 1K miles so it should last and then I plan to rebuild the trans probably over the winter.

 

[A. G. Olphart]

If you look one of the assemblies over, it would be pretty easy to ENLARGE the FLUID capacity either between the cover and piston top as well as the piston's inside, would this get the same results as more surface area?

HOW

Nope... Transmission pressures are measured in pounds per square inch, and are applied against the area of the piston. So actual pressure in pounds that is exerted on the band's apply pin is the band apply pressure times the area of the piston in square inches.