Racing Automatic Transmission question

I have very little automatic tranny experience. I'm looking for a 1 way clutch/sprag clutch/over run clutch/free wheel unit, it appears to have many names.

I was thinking about sprags in an automatic. Generally speaking when a tranny is made into a "race" automatic, are the sprags upgraded to something stronger? Or maybe they are changed so they can handle the extra RPM?
Or generally, do the stock sprags get used?

Thanks

 

In a TH400, they generally employee a sprag with many more rollers than factory, as that is where the strength comes from. More contact area. In a glide there isn't a sprag, so.......(minus the converter sprag). TH350's have a sprag too i believe.

I haven't been in a 727, so i'm not sure on those guys.

 

Although the terms often overlap,

An overunning clutch (as usually found on a starter) generally uses rollers that are captured between an inner and outer race and are held in groove that is smaller at one end than the other when they roll in one direction they are forced to the smaller end of the groove and are trapped under pressure between the inner and outer race so that the two are locked together, generally a spring of some sort is used to aid push the rollers slightly toward the thin end of the groove.


A sprag on the other hand has elements called sprag's that are sandwiched between an inner and outer race, the most common shape for a sprag is a dogbone where it pivots in the center of the "bone" and one end meets the inner race and the other end meets the outer. The length of the dogbones is such that they can only rotate partway before becoming wedged between the inner and the outer race. The actual sprags are generally referred to as elements and the entire unit is referred to as a sprag, in a turbo 400 a 36 element sprag is considered heavy duty though greater numbers of elements are available.

A sprag generally requires more precise tolerance than a roller clutch, a roller clutch also generally needs more degrees of rotation to lock up than a sprag a sprag can also generally hold more torque than a roller clutch in the same area and has less rotational wieght. So as you can see a sprag is well suited for high load apps like transmissions and a roller clutch is well suited for cheap apps like a starter drive.

PS A tourqueflite 707 or 727 uses a big ass roller clutch that is pressed in the case, due to the design (press fit) it often spins in the case, you can then but a new one ( called a bolt in sprag but still just a roller clutch ) these designs (press fit) were so weak they almost failed in racing, hell sometimes a 16 year old kid with a 6 cyl would break one loose playing around neutral dropping his van......Don't ask me how I know!

 

That's your 16 yr old story now, but what was it back than when you explained to your parents what happened??

 

Luckily it was my van and I new Bigfoot at ATI so he told me what I hurt. I pulled the trans apart, filtered the fluid through cheesecloth, got the roller clutch with the bolt holes for 37 bucks and put it all back togther and it was fine...old fluid,pan gasket and all.

Now as far as the old man goes, he used to drink the black label long necks in the returnable bottles, every time I would borrow his Pinto the next day he would say I was "Gear Jhamminge!!" in his best Swedish accent , well after about three months of getting busted for this offense, he told me and my best friend he had a "system". He used to keep the Black Label bottles in the back of the car and made a little tic mark with a crayon at each corner