I know that Dog Box Tranny's are built for the sole purpose of withstanding high horsepower/tourque output of highly modified cars.

I know all the pros of these trannies but what are the cons? What disadvantages does it have over the OEM one if daily driven/street driven(Noises, hard shifts, etc...)?

Any feedback bad or good...

 

The main problem with a 5mt is the case flex. It seperates the gears slighty then crushes them with tremendous force. A stronger gearset though will last longer will not last forever.

A STI 6 speed tranny has little flex and to my understanding is a far superior choice in transmissions.

Dog boxes also have straight cut gears to my undestanding. If so they will be noisey like reverse is at high speed.

 

Dog or straight-cut gears (photo off of TurboXS website.)


syncro gears


I have no idea of the actual mechanics behind why, but straight gears are so much harder to shift because you have to rev-match (engine speed has to be at such and such revs in order for you to be able to shift smoothly), where syncro gears have syncros to assist you when you shift.

Also, straight gears are much noisier (hence what Roadspike is talking about. Your reverse gear is straight cut.)

That's about all I know and 'know' is relative.

 

its not that straight cut gears are harder to shift by themselves, its that with all the dog box trannies sold right now, they make the gears physically larger so there is not place for a synchro; hence the difficulty shifting between gears. they require perfect rev matching so they synch together without grinding, so you the driver has to perform the function of a synchro everytime you shift gears.

 

Not perfectly true..

A dog box yes doesn't use synchro's but actually gets its name by the synchronizer. Its a set of usually 6 dog teeth. These teeth under extreme revs would grind but during mostly synchro'ed shifts slam the gears into synch.

Just for example you can clear see the dog teeth on the rings here


And for the record you can get better synchro gearsets if you believe dog box sets are a lil too much harshness for your comfort

Edit:
Synchro sets even with straight cut gears if you like.

 

neat, didn't know that. learn something new everyday

 

Straight cut gears are stronger (more contact surface between gears at any given moment) while the helical cut gears are much quieter. That's why the gearsets meant for strength use straight cut and OEM gears are not. The shifting differences, as noted above, come from synchro differences (or absence).

 

Straight gears also (ideally) only transfer tangential forces - torque. Helical gears will transmit axial forces as well as torque so some of the engine effort is trying to push the gears into the thrust bearings instead of trying to turn the shaft.

 

I was taught that the straight cuts are actually not neccessarily stronger becuase its less tooth metal (sideways is longer)

However it works better becuase the load placed on the gear on a helical gear is sideways which puts alot of pressure on the bearings, straight cuts however do not have this issue. Therefore in higher torque apps the straight cut works better becuase of how the pressure is distrubuted on the gears.

 

The straight cut gears have a larger contact area between teeth, which reduces the stress on the metal. It's like the difference between hitting a nail into a piece of wood and hitting a railroad spike. Same amount of force applied, different results.

 

so would it be difficult to shift in a wrx with a dogbox...as an everyday driver??

-freddie

 

Yes. A dogbox makes lots of noises and is very hard to be smooth with. It will make you look like a noob with a manual shifter.

 

YES!!!! Just what I always wanted.

thanks bro

-freddie

 

Freddie, you know you share a screen name with another guy who has or had a fairly infamous WRX, don't you.

Anyhow, I uploaded this article I stole from MRT about Dogs:
MRT.doc

 

lol...I think I was first to have it!! Also, I HAD fairly infamous WRX too. Plus, my last 3 cars had the LP #'s as 1***2NV. (WRX, SVT, VW)

Hey, thanks for the link...good stuff. I already have a JDM Sti 6 speed...just wanted some info on the dogbox.

thanks again

-freddie