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-   -   Differences between dogbox, dog teeth, syncho, 915, G50, modern gearboxes (http://forums.pelicanparts.com/off-topic-discussions/914295-differences-between-dogbox-dog-teeth-syncho-915-g50-modern-gearboxes.html)

J P Stein 05-18-2016 07:09 AM
Quote:
Originally Posted by Matt Monson (Post 9125520)
JP,
Have you seen what Britain has done with the gearbox since? I'll see if I have pictures. 2 Spd 930 dog box now.
I haven't seen the guts of his 2 speed. I was surprised to learn that he converted the 930 to a 2 speed. Can he swap it back to a 4 speed?

That beastie would be a hell of a track car with a couple more gears. The Porsche crowd would be in for a shock......that is an excellent case for "Modern". He's pulling 380HP at the wheels for now (@ 2.0L) at (WAG) 1/4 the price of Porsche power.

javadog 05-18-2016 07:19 AM
Quote:
Originally Posted by J P Stein (Post 9125502)
...but you still couldn't power shift it. (right foot flat to the floor, side step the clutch pedal while going for the next gear).
I would never shift any gearbox that way, even a dog box. You need at least a momentary cut in power, if nothing else to keep from over-revving the motor, so I think that's outside the scope of this discussion and not an indictment of a Porsche gearbox.

Probably a good thing you took out 1st and reverse from your gearbox...

JR

J P Stein 05-18-2016 07:38 AM
Quote:
Originally Posted by javadog (Post 9125642)
I would never shift any gearbox that way, even a dog box. You need at least a momentary cut in power, if nothing else to keep from over-revving the motor, so I think that's outside the scope of this discussion and not an indictment of a Porsche gearbox.

Probably a good thing you took out 1st and reverse from your gearbox...

JR
I admit ya gotta be quick.....practice helps....I did learn how to rebuild a T-10.
I tried to do it "once" with a 901 box.....I got off gently.

Your statement shows a lack of experience...... maybe OK in theory.

I now have a Miata. That 6 speed is almost as slick shifting as a T-10. I've never driven a Porsche with the BW syncro set up.......and ,as a result, with hold opinions
of them.

javadog 05-18-2016 08:02 AM
Quote:
Originally Posted by J P Stein (Post 9125666)
Your statement shows a lack of experience...... maybe OK in theory.
a lack of experience... no, don't think that's the case. I have plenty of that.

I just choose to treat my gearboxes, and everything else, like they should be treated. I don't drive (or ride, in the case of bikes) like a Neanderthal...

I'm out of here, I think. Sugardude has his questions answered and I can't stand to listen to red-breard's acid trip again...


JR

Matt Monson 05-18-2016 08:10 AM
Quote:
Originally Posted by J P Stein (Post 9125629)
I haven't seen the guts of his 2 speed. I was surprised to learn that he converted the 930 to a 2 speed. Can he swap it back to a 4 speed?

That beastie would be a hell of a track car with a couple more gears. The Porsche crowd would be in for a shock......that is an excellent case for "Modern". He's pulling 380HP at the wheels for now (@ 2.0L) at (WAG) 1/4 the price of Porsche power.
Definitely not reversible. It's hydraulic clutch and directly actuated on the shift rod. There is no longer a selector rod in it. Really good details and pictures are in this thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/762965-worlds-lightest-930-transmission.html

red-beard 05-18-2016 09:19 AM
Holy crap! The old transmission part prices are out of control. I remember complaining when sync band went from $20 to $40. Wow. Rebuilding a 901 will be mighty expensive these days.

Matt Monson 05-18-2016 09:59 AM
Quote:
Originally Posted by red-beard (Post 9125833)
Holy crap! The old transmission part prices are out of control. I remember complaining when sync band went from $20 to $40. Wow. Rebuilding a 901 will be mighty expensive these days.
Price a 1st/R slider for 901 or 5th/reverse for 915. Crazy expensive these days.

masraum 05-18-2016 12:58 PM
Quote:
Originally Posted by Matt Monson (Post 9125522)
It's seem there's only one choice. :) My LSD.
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.

kusiobache 05-18-2016 03:06 PM
Quote:
Originally Posted by Geary (Post 9125565)
Two things are going on with the earlier Porsche system:



As the shift sleeve ages, it develops a ridge on each and every engagement tooth. This essentially narrows the gap that the corresponding dog teeth must plug into. Those sharp little ridges slowly replace smooth tooth flanks as the initial contact point.

http://images.thesamba.com/vw/gallery/pix/1062236.jpg


Sorry, but could you elaborate on how/why it narrows the gap? I would think the engagement teeth wearing down would increase the gap, unless you are saying the dog teeth make less contact?

sc_rufctr 05-19-2016 05:54 AM
<iframe width="560" height="315" src="https://www.youtube.com/embed/wCu9W9xNwtI" frameborder="0" allowfullscreen></iframe>

J P Stein 05-19-2016 06:07 AM
Quote:
Originally Posted by masraum (Post 9126164)
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.
I went with a torque biasing diff from Guard many moons ago and never regretted it.

A top notch product which, unobtrusively, dose it's job.

Matt is now the HMIC there.

masraum 05-19-2016 12:56 PM
Quote:
Originally Posted by J P Stein (Post 9127087)
I went with a torque biasing diff from Guard many moons ago and never regretted it.

A top notch product which, unobtrusively, dose it's job.

Matt is now the HMIC there.
That's what I was thinking. My last car, turbo miata, had one, and it seemed to work well on the street.

Geary 05-19-2016 04:21 PM
Quote:
Originally Posted by kusiobache (Post 9126374)
.. could you elaborate on how/why it narrows the gap? I would think the engagement teeth wearing down would increase the gap, unless you are saying the dog teeth make less contact?
The pointer shows the spot where material is scuffed and peeled over by the Porsche synchro band. This sharp spot is found on each and every tooth of a worn out shift sleeve.

If you were to test how smoothly new engagement teeth plug into a new shift sleeve and compare this against the worn out parts, the difference is quite evident.

notfarnow 05-19-2016 04:42 PM
http://forums.pelicanparts.com/uploa...1463704739.jpg

I refreshed my 915 over the winter, and was so damned proud of myself that I couldn't bear to just put it in the garage until it went in the car.

Hoping to get the car buttoned back together this weekend, and I am REALLY anxious to see how it shifts.

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.

Geary 05-19-2016 05:05 PM
Quote:
Originally Posted by Geary (Post 9127961)
The pointer shows the spot where material is scuffed and peeled over by the Porsche synchro band. This sharp spot is found on each and every tooth of a worn out shift sleeve.

If you were to test how smoothly new engagement teeth plug into a new shift sleeve and compare this against the worn out parts, the difference is quite evident.
Another clearer stock photo showing the deburring and removal of all sharp edges. This is generally a waste of time with worn sleeves, as the working dimensions are already on the high side.

http://images.thesamba.com/vw/gallery/pix/1116841.jpg

red-beard 05-19-2016 05:40 PM
Here is a worn slider - Photo is nearly 15 years old!

The slider wear in two ways: 1) The sync band contact spreads metal, making the double pointed areas wider, making it harder for the dog-teeth to engage. And the pointed areas wear against the dog-teeth, rounding, usually because the sync band is worn and not making good contact.

http://forums.pelicanparts.com/uploa...1463708034.jpg

Sorry this first gear slider is a little out of focus, but you can see the rounded points.

http://forums.pelicanparts.com/uploa...1463708390.jpg

The dog-teeth are softer than the slider, so they wear out faster...

red-beard 05-19-2016 05:50 PM
A good shot of a rounded, worn slider

http://forums.pelicanparts.com/uploa...1463708517.jpg

Here is my attempt to clean up a 1st gear slider in a 901. I used a file in between the grooves to bring them back to spec. Then I used a dremel to repoint the triangular area. At the time, 1st gear sliders were not just expensive, they were hard to find. A repointed slider with a good sync band and new dog-teeth restored function.

http://forums.pelicanparts.com/uploa...1463708940.jpg

http://forums.pelicanparts.com/uploa...1463708964.jpg

kusiobache 05-19-2016 05:55 PM
Differences between dogbox, dog teeth, syncho, 915, G50, modern gearboxes
 
Quote:
Originally Posted by Geary (Post 9127961)
The pointer shows the spot where material is scuffed and peeled over by the Porsche synchro band. This sharp spot is found on each and every tooth of a worn out shift sleeve.



If you were to test how smoothly new engagement teeth plug into a new shift sleeve and compare this against the worn out parts, the difference is quite evident.


Quote:
Originally Posted by Geary (Post 9128014)
Another clearer stock photo showing the deburring and removal of all sharp edges. This is generally a waste of time with worn sleeves, as the working dimensions are already on the high side.



http://images.thesamba.com/vw/gallery/pix/1116841.jpg


Quote:
Originally Posted by red-beard (Post 9128046)
Here is a worn slider - Photo is nearly 15 years old!



The slider wear in two ways: 1) The sync band contact spreads metal, making the double pointed areas wider, making it harder for the dog-teeth to engage. And the pointed areas wear against the dog-teeth, rounding, usually because the sync band is worn and not making good contact.



http://forums.pelicanparts.com/uploa...1463708034.jpg



Sorry this first gear slider is a little out of focus, but you can see the rounded points.



http://forums.pelicanparts.com/uploa...1463708390.jpg



The dog-teeth are softer than the slider, so they wear out faster...


Thank you both very much for the pictures and enhanced explanation.

red-beard 05-19-2016 06:25 PM
901 gear stacks before being put back in a transmission

http://forums.pelicanparts.com/uploa...1463709386.jpg

Some fun pictures - really broken stop blocks and brake bands

http://forums.pelicanparts.com/uploa...1463709620.jpg

Geary 05-19-2016 08:08 PM
Quote:
Originally Posted by red-beard (Post 9128102)
Great shot, James .. mind if I borrow it?


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