straight cut gears?

[grk nickafis]

Whats the benefit? why does it whine?

[tg]

Benefits are that there is less stress on the thrust bearings compared with helical gears (helical gears exert force sideways on the shaft and thus on the thrust bearings because their gears are on an angle).

They wine because the amount of time that the gear has to transition into the next gear is significantly less than with helical gears... basically the entire face of the gear engages at the same time, instead of gradually like a helical gear. Think about a frisbee, if you were to stand it on its side and flip it onto the rounded side (the top of the frisbee), it wouldn't make a clapping sound when it hit the ground, but if you did it the other way, it would because all of the surface is making contact at the same time.

Your car has 1 straight cut gear reverse.

[car nut]

Straight cut gears are cool, but they'd be expensive for your car. I've never heard of a set made for 300zx, and considering that pre-made sets run you $4k+, so a custom set would probably be double that. Plus, straight cut gears can be a pain to get used to unless you regularly rev-match and are good at it. Otherwise you'll destroy them.

[grk nickafis]

http://www.youtube.com/watch?v=a-k3YAjIQzI
thats why i asked :p.

ok so they give you better gear ratios? im still alittle confused.

[car nut]

Straight cut gears do not have synchros. Instead of using the clutch to disengage the transmission and then having synchros (think of a synchro as a small, simple clutch) to match the gear speeds together and "synchronize" the two, YOU (the driver) uses your right foot to match the revs for each gear and then bang the shifts out.

Helical:

Straight cut:


See the differences? In the first picture, the gears have a curve to match them together (the curve is the beginning of a helix hence the name), but in the second, all the gears have "straight cuts" right into each other. The reason for the helical cut in most cars is that it creates a very silent transmission (like tg said, go out and put your car in reverse. Hear that whine? Reverse on 99% of cars is straight cut). But, like tg said, they exert a lot of force on the transmission case, so in a high horsepower setting you could blow up your transmission with a helical cut gearbox. Straight cut gears don't have this problem, but while you gain in strength, you lose in noise level and shifting effort (you really gotta bang throw the gears).



See those little shapes? Those are what replace the synchros in your transmission. That's why you need to rev-match and bang the gears in. (sometimes, the shapes look like dogs, hence the nickname "dogbox")

[grk nickafis]

haha word. I get it now.

thanks

[bartZ32tt]

Damn, if you read the comments he said it cost him $10000 to install!

[tg]

Yeah, I got a quote on a set, $9600 not including install

[raremotive]

Straight cut gears do not have synchros. Instead of using the clutch to disengage the transmission and then having synchros (think of a synchro as a small, simple clutch) to match the gear speeds together and "synchronize" the two, YOU (the driver) uses your right foot to match the revs for each gear and then bang the shifts out.


See the differences? In the first picture, the gears have a curve to match them together (the curve is the beginning of a helix hence the name), but in the second, all the gears have "straight cuts" right into each other. The reason for the helical cut in most cars is that it creates a very silent transmission (like tg said, go out and put your car in reverse. Hear that whine? Reverse on 99% of cars is straight cut). But, like tg said, they exert a lot of force on the transmission case, so in a high horsepower setting you could blow up your transmission with a helical cut gearbox. Straight cut gears don't have this problem, but while you gain in strength, you lose in noise level and shifting effort (you really gotta bang throw the gears).


See those little shapes? Those are what replace the synchros in your transmission. That's why you need to rev-match and bang the gears in. (sometimes, the shapes look like dogs, hence the nickname "dogbox")

Actually, they do have sychros, they opt to dog engagement. They are just much larger in gap. It allows for clutchless shifting...

Fast forward to 4:50 to see how and wtf I am talking about.

http://www.youtube.com/watch?v=-fA94Sxiu4c

[ArticDragon192]

http://www.youtube.com/watch?v=a-k3YAjIQzI

Raddest thing ever. Clutchless shifting. Sweet as race car sound. Just banging through the gear. This particular Z is running a PPG gearset.

[grk nickafis]

i know, i already posted that video up there. it made me curious.

[car nut]

Actually, they do have sychros, they opt to dog engagement. They are just much larger in gap. It allows for clutchless shifting...

Fast forward to 4:50 to see how and wtf I am talking about.

http://www.youtube.com/watch?v=-fA94Sxiu4c

Great video! I don't really see what you're saying though. Are you saying that dog engagement is a type of synchro? Or that you can have a synchronized, straight-cut gearbox? Cause from that video I'd have to agree with you.

http://www.youtube.com/watch?v=a-k3YAjIQzI

Raddest thing ever. Clutchless shifting. Sweet as race car sound. Just banging through the gear. This particular Z is running a PPG gearset.

Better video