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Discussion Starter · #1 · (Edited)
So I cracked open my brand new never used P11 tranny today to throw in a Nismo LSD. I've been inside different manual trannies before but found something today that I can't figure out, and I spotted it immediately after opening it up.

This:

This the reverse gear. That strange disc with teeth on top is called the Sub-Gear. So you're thinking no big deal right? Well.....




Look at what happens when we spin the gear 180 degrees and see the other side:



Got your attention now? Yeah well guess what? It's got one more tooth than reverse gear. So that means that the entire time the *clutch* is engaged and the engine is turning the input shaft that reverse gear is turning and that 'Sub-Gear' is turning slightly slower. Note I said the ENTIRE time, NOT just when you're in reverse but ALL THE TIME. The reverse idler gear (missing from this picture, rides on the input shaft and reverse 100% of the time)

Here is another pic to show the gap between:


I don't understand what this does? Why would you want this friction constantly going on?









Also of note, I have never seen input teeth shaped like this:


These are on 2nd and 3rd gear. One good thing, the design looks STRONGER. :) The reset of the input teeth look like normal B13/B14 input teeth with the pyramid design.




 

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IF I remember right its to make reverse easier to engage along with quieter and not so whiny.....
being how its on a "luxury" car (P11) and all. Again, dont quote me, but IIRC I dont think the B15 trannies have that configuration.

Reverse gears are alsoo comonly staright cut and I noticed the P11s werent. The tranny is way more complex than the B13/14 ones. All in a good sense.
 

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Discussion Starter · #3 ·
IF I remember right its to make reverse easier to engage along with quieter and not so whiny.....
being how its on a "luxury" car (P11) and all. Again, dont quote me, but IIRC I dont think the B15 trannies have that configuration.

Reverse gears are alsoo comonly staright cut and I noticed the P11s werent. The tranny is way more complex than the B13/14 ones. All in a good sense.
Nope. No disrespect but you're wrong on both counts. It has nothing to do in regards to engaging reverse(as I said above it's turning 100% of the time) and B15 tranny's have it also. I checked the FSM and also found a pic on the forum of a B15 tranny gear stack.

Two other things are also rare about reverse in this tranny. One thing you mentioned (and I also spotted and mentioned in the original 2005 coalitionSE-L B15/P11 thread here: http://www.sr20forum.com/933865-post25.html) is that it's helical which makes it as quiet as other gears and also it has a synchro which makes it easier to shift into.

When reverse is not selected, that sub-gear spins at a different rate riding on a mini-shaft of sorts machined on the reverse gear itself, which in turn is free floating and turning at a different rate than the mainshaft it's riding on. When reverse is engaged all the above is the same except of course reverse will then be spinning the same speed as the mainshaft because IT will be turning the mainshaft. Very very wierd...makes no sense what that sub-gear is doing.......
 

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No disrespect taken, just tryin to answer a question, but it seems you know what the answer already isnt rather than what it is....

I still think it has something to do with synchronization and engagement. The old trannies never had a synch'd reverse, B155 and P11 do.... They wouldnt just put it there to spin (either faster or slower) and sling fluid around lol

but oh well. Im more than happy with the P11 trans so I havent taken the time to figure out EXACTLY how and why it works rather than just accepting that it does :)


Seems like a similar idea from a patented design:

"A gearbox-transmission, especially for power vehicles, with synchronized reverse gear, an intermediate-gearwheel providing for the reversal of direction consists of two loose-gearwheels located on the same axis which is beside the input and output shafts, of which the one loose gearwheel engages the input-shaft via a loose-gearwheel and the fixed-gearwheel of one forward-gear, and the other engages the output-shaft via the loose-gearwheel and the fixed-gearwheel of another forward-gear. The two reverse gear loose-gearwheels are connectable with each other by means of a shift-clutch. In this way no additional gearwheels are needed on the input- and output-shaft for the reverse-gear so that the structural length of such a transmission can correspondingly be reduced."
 

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Number of teeth has nothing to do with speed, outside diameter does. A gear with 1 million teeth and a 1" OD spins at the same rate as one with a 1" OD and 12 teeth (like those people in TN :D). Is that gear enmeshed with anything else? I can't tell in your picture, but I see air between it and the input shaft.

EDIT: Or does that gear and the reverse gear enmesh with the same gear? If so, then ignore above.
 

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Discussion Starter · #6 ·
Number of teeth has nothing to do with speed, outside diameter does. A gear with 1 million teeth and a 1" OD spins at the same rate as one with a 1" OD and 12 teeth (like those people in TN :D). Is that gear enmeshed with anything else? I can't tell in your picture, but I see air between it and the input shaft.

EDIT: Or does that gear and the reverse gear enmesh with the same gear? If so, then ignore above.
Oh really? Hmm, well let's see. (You set your self up for the following :D)
http://science.howstuffworks.com/gear-ratio2.htm
and I quote:
'They make it so that slight imperfections in the actual diameter and circumference of two gears don't matter. The gear ratio is controlled by the number of teeth even if the diameters are a bit off. '

There's not really air beneath it as it is sort of chamfered or bent just behind the row of teeth. Looking at the FSM blow up, it shows that it slides around a collar on the reverse gear directly below it, sort of riding on it. No other pieces there. It has a big lock ring on that collar to keep against the reverse gear tight. So tight that it takes quite a bit of effort with a flatbade screwdriver wedged vertically between two misaligned teeth to twist and move.

As to your last question....YES, DUH:rofl:, that gear and the reverse gear enmesh with the same gear, HENCE my statement in the original post 'So that means that the entire time the *clutch* is engaged and the engine is turning the input shaft, that reverse gear is turning and that 'Sub-Gear' is turning slightly slower.'
 

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Discussion Starter · #7 ·
I think we have a winner. This is from the MotoIQ forum where I created the same thread:

'It reduces backlash noise by adding a slight one way frictional tension on stuff. A lot of other Nissan trannys use this sort of thing. They took it out of the 370z as a cost down and it has a lot of input shaft rattle complaints. The Z32 and Z31 as well as a lot of the older trannys have it.'

I also found this: http://www.4wdonline.com/Nissan/GU/1999ute.html
"The latter is chain-driven with "a non-backlash mechanism which comprises a sub-gear with one more tooth than the outer gear which is tensioned by a dish spring to maintain chain tension."
 

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Oh really? Hmm, well let's see. (You set your self up for the following :D)
http://science.howstuffworks.com/gear-ratio2.htm
and I quote:
'They make it so that slight imperfections in the actual diameter and circumference of two gears don't matter. The gear ratio is controlled by the number of teeth even if the diameters are a bit off.'
Touche, however, the diameter is still important. The teeth have to be about the same size or they won't mesh well, and you can only fit so many teeth on a given circumference.

I think we have a winner. This is from the MotoIQ forum where I created the same thread:

'It reduces backlash noise by adding a slight one way frictional tension on stuff. A lot of other Nissan trannys use this sort of thing. They took it out of the 370z as a cost down and it has a lot of input shaft rattle complaints. The Z32 and Z31 as well as a lot of the older trannys have it.'

I also found this: http://www.4wdonline.com/Nissan/GU/1999ute.html
"The latter is chain-driven with "a non-backlash mechanism which comprises a sub-gear with one more tooth than the outer gear which is tensioned by a dish spring to maintain chain tension."
Word. I thought it would cancel noise and vibration because of differing speeds, but the tension sounds right as well.
 

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Discussion Starter · #10 ·
so its to improve engagement and make it quieter......


sorry for not saying it so pretty :rolleyes:
Improve engagement = not

Make reverse quieter = not

It makes the *input/mainshaft* shafts quieter. You specified reverse. Reverse wouldn't whine because it's helical.

What you said is so general. It's like saying hey man it does SOMETHING. You think? :rofl:
 

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whatever dude. Just cause I didnt give you a cut and paste answer regurgitated from a tech manual....that didnt make you happy so Im automatically wrong.

Try using your own intuition and understanding that other people can make decent assumptions, sometimes generalized, without having to rely on the internet and crap like "howstufworks" and "wikipedia" as their main and ONLY source of intelligence.

So sorry for trying to direct you in the right direction TRANNY GOD.... George Peters aint got **** on you :rofl:

BTW professor dickweed...backlash is a physcal phenomena associated with torque and gear engagement.... so reducing backlash means improving engagement... either by making the gears "mesh" more smoothly or reducing torque (not good-even you will agree)

again, sorry for trying to hint at things and figure stuff out sans google, tranny god.. Let us know when you design an 8spd tranny for SE-Rs :rofl:
 

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I think you all have sand in your vaginas. You guys are nitpicking each other's posts, and getting no where. I'm not saying you guys need to play nice, but if each answer is not 100%, the other person is wrong.
 

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Yeah I guess, man. No answer is ever 100% its a forum.

I just think if someone posts a question and other people try to provide some sort of intution, even if its a generalized idea, (commonly refered to as a hypothesis, for those who dont live their lives by Google), the person asking the question should have a little more humility than to just say "NO YOURE WRONG, NEXT"...cause rememeber, he's the one asking the question and any guess that person made, in this case were no better or even close....

The whole point of asking questions is to come to a conclusion based on several inputs and sources. Not just act like youre king **** and only the answer you want to hear, which in this case is just being blindly followed, is the only correct answer and everyone else is idiots.

Again, rememeber who is asking the question....cause they couldnt come about any answers on their own.

In the end, i guess he found the answer he was looking for so thats all that matters (even though he doesnt understand what half of it means). So screw it...no need to waste more time here....

Sign me up for 2 of the Reynolds 8-speed Sequentials when it comes out, thats all.
 

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