Differences between dogbox, dog teeth, syncho, 915, G50, modern gearboxes

[red-beard]

Sure, go ahead

[sc_rufctr]

My 915 from 7 years ago. Note, first gear dog teeth on the left.

[red-beard]

Peter, I hope this is a before picture

[sc_rufctr]

Yes, Before... After 7 years and many miles she still shifts sweetly.

[Matt Monson]

Originally Posted by masraum

Checked out your site. Looks like you do have both clutch and torque biasing type. That's what I was asking, if you had an opinion/recommendation for an enthusiastically driven street car.

Sorry, I have a tendency to be technically strict. Quiafe tells you they make an LSD. They make a torque biasing differential. All of the gear driven differentials go open at the limit, therefore they are not limited slip differentials. So when you said lsd I was only talking lsds.

Yes, I think our torsen diffs are a great product. Its what I run in my 914. The midengine cars don't seem to need the same locking under braking that 911a do unless you are racing it. For back road driving at $800 less the tbd is a great alternative. Way more traction on power with no need to rebuild it, though in a streetapplication our lsds usually go 8-10 years between clutch jobs.

[masraum]

Thanks for the response, Matt. I wish I was ready to buy, but when I am, you'll be the second to know (behind the CFO )!

[red-beard]

Originally Posted by notfarnow

I've had the more typical Borg Warner style transmissions/synchros apart before and it is pretty intuitive when the parts are in your hand. However, even after having the synchros apart in my 915 transmission, I still don't really get it.

Here is everything on the shaft.



Here is a gear (4th gear) with the sync band. The dog-teeth are pressed onto the gear and are the part that engages the slider.



Here is a slider starting to engage 4th gear. The slider first touches the synch band. It is not just friction, the sync band is larger than the slider. The slider squeezes and slight compresses the sync band. This brings the transmission to the same speed as the engine.



As the slider continues towards the dog teeth, it may not be perfectly lined up. This is where the "points" come in. if there is a little offset between the teech and sync band channels, the points create force to rotate the gear/slider and direct them to correct engagement.



The way this transmission works, one shaft is attached to the engine, the other too the wheels. The power comes in the pinion shaft and out the drive shaft. Each "gear" is really a driven gear and a drive gear, one of each shaft. The ratio of size determines the gear ratio.

In every case, one of the gears in a set is fixed to a shaft. The other one rides on a caged needle bearing. ONLY when the slider engages a gear will that gear lock to the shaft. Under the slider is a triangular piece which is fixed to the shaft.



The shift forks ride on the outside groove of the slider. (This is the 1st gear slider, so it only engages one direction). The shift shaft moves forwards and backwards with the movement of the main gear selector.



Each shift shaft has a notch in it. When the transmission is in neutral, all of the notches are lined up. As you move the gear selector from side to side, it will line up with one of the three shift shafts. When you move the gear selector forward and backwards, it will move the shaft shaft forward or backwards and cause the slider to move forwards or backwards.

[red-beard]

Here is a good and bad sync band