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H-Pattern Gear Sets: Synchro / Dog Box 

Gear Tooth Profiles: Straight Cut / Helical Cut 

H-Pattern gear sets is where it all began for PPG, faced with the need for performance gear sets to replace OEM gear sets for high performance cars,

Simon Pfitzner (MD) and his then business partner soon realised their was an opportunity to manufacture and supply this growing marketplace with high performance gears . 


Soon after PPG was born and as they say, "the rest is history".....


H-Pattern gearboxes in road cars come as Synchromesh helical tooth designs from the factory, this enables smooth changes and quiet operation in use and usually lasts the life time of the car.


However since cars have been raced back in the early 1940's their has been a requirement for gearboxes to shift faster than synchromesh could allow without damage being caused.  The product that evolved for racing was referred to as a "Dog Box". 


"Dog Box" is usually a Dog Engagement type arrangement and thus eliminating the synchromesh system standard cars use for smooth gear changes. 


The dog engagement has its history in old agricultural type machinery and required a fair degree of mechanical sympathy to change smoothly.


The speed of operation is not limited unlike the synchromesh system they replace, making them ideal for motorsports application.

What is a synchro?
What does 'Dog Box' really mean?

We get asked all the time? What part actually does what operation in a gearbox! Essentially the synchro or dog teeth allow each gear to engage another gear.
The straight or helical tooth design run in constant mesh with the mating gear to make the gearbox drive the output shaft.

Synchromesh or synchro as its referred too is used in the majority of OEM car gearboxes   

Helical profile tooth design for quiet 

operation in road cars.  

Images shows a stock TREMEC Synchromesh gear. The gear is
Helical tooth profile with 
synchromesh design for smooth engagement.

Dog tooth engagement, ideal application for
motorsport gearboxes

Helical profile tooth design 
for quiet operation.

Dog tooth engagement, ideal application for
motorsport gearboxes

Images shows A HONDA Dog  gear. This gear is Helical tooth profile with 

Dog engagement design for super fast engagement.

Straight cut dog engagement 

design for maximum strength

in heavy duty applications.

The majority of our systems are supplied straight cut. 

Images shows a HONDA Straight cut Dog gear.

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