Why hasn't anyone ever installed a sprag clutch on the input shaft of a manual transmission?

That would allow you to take your foot off the gas without disengaging the clutch- until the car slowed to a point that the input shaft was turning slower than the flywheel, right? I don't know a whole lot about transmissions, but if I remember correctly don't all automatics have this feature?

 

Yes pretty much all autos have it. It is usually the weak point in the system. They don't like shock loading.

 

So how does a trans brake not hurt them? I just want to have my cake and eat it too. Is there any way to make this work on a manual?

 

It is loaded tight on the dodges when you pull to the line. If you let them have slack then shock load them you can have a catastrophic failure. The turbo 400s in the chevs I think can fail when 1-2-3 bunout is done. They have the cushion of the torque converter. Clutches don't have any cushion. One other note is that when a race dodge transmission is built they generally have the low reverse band not activate in first. The only thing holding it is the drum is the sprag. So on decel in first gear it will just coast and not upshift. If the driver nails the throttle and goes from a free running sprag to a loaded spag it may result in a failure. That would be kinda like the idea you propose. No builder of a trans like this will even build one if you are going to run it on the street. Most autos feel like they free run on the sprag but they don't they just upshift in gears and slip the converter. Do what I do with a manual and kick it into nutral just as the gears sync and you don't have to even step on the clutch.

 

Okay, that makes sense. But I have a few quick questions for you.

1. What is a 1-2-3 burnout? Is that going through the gears as you burnout or....?

2. What about on a "clutch turbo" that is, a clutched turbo400 like people used to run a long time ago? Did they just remove the sprag clutch altogether?

 

I just mean a third gear burnout. Far as I know they can be hard on the turbo 400s. As far as the spragless 400s. I have no idea how they do those. May be add a extra set of clutches.

 

So are you saying that there actually were automatic transmissions (specifically turbo 400's) that didn't have sprags?

 

Jeffco trans is built like this. Pretty sure.

 

At the bottom of the page there is a bit of a explantion of the spragless 400.

http://www.extremeautomatics.com/transmissions/th400extremespragless.html