Gearspeed Dog Box Transmission Assembly - Honda Tuning Magazine

One of the most important factors of a purpose-built drag car is the transmission. As we already know, the tranny is essential to transferring all of that well-earned power under the hood to the drive wheels. Often drunk with power, many leave the transmission as an afterthought. Due to the fact that Honda transmissions were simply never designed to take the extreme, constant abuse of drag racing, the incredible stress can cause significant damage to vital components. The novice crowd oftentimes invests all of their money into the motor build and very little into the transmission. They may feel that driving a Honda down the strip for short bursts will do little damage to their stock gearboxes but that certainly is not the case. The reality of the situation is that the strengthening of a transmission should never be overlooked. Honda transmissions were built with durability and, most importantly, reliability in mind, but that only applies to “normal,” long-term driving. Banging gears while blasting down the 1320 repeatedly with monster power under the hood can yield a very short-lived transmission.

For drag racers experiencing issues with the longevity of their factory gearboxes, their prayers were answered with the advent of the dog box transmission. Dog box gearsets are the key to having a more durable, drag-prepped transmission. While factory transmissions are comprised of many intricacies and gears that are angled for smoother shifting, dog boxes are much simpler—and straight to the point. Their gears are designed to be straight-cut and have fewer teeth than stock, so as to handle faster shifts in high-horsepower applications. Less moving parts (no synchros) and increased reliability make them a prime choice for high-level competitors. Gearspeed adds, “Synchromesh transmissions became the standard in the majority of present-day vehicles for their ability to engage gears quietly, smoothly and offer years of trouble-free operation under normal driving conditions. The main chore of the synchro is to slow down the gear as pressure is applied from the sleeve to allow the selected gear to engage. This works great on your drive to the local grocery store and spirited drives through the hills. Now sit in the seat of a 500-plus-horsepower drag car and the synchromesh transmission becomes your weakest link—unable to keep up with high-rpm shifting and prone to failure if clutch operation is not on point. Great improvements have been made with the introduction of the carbon-coated synchros to aid in syncing gear engagements much more efficiently, but when it comes to race cars where every second counts…much is left to be desired. In comes the ‘dog engagement’ transmission. In place of the synchro assembly you will find ‘dogs,’ which are the stubby teeth in place of the synchromesh teeth that will mate with the sleeve that contains the same number of openings and allow for fast instant engagement. Dog engagements need to be shifted quickly to minimize wear on the dogs. The faster you shift, the better. Your average granny shift will destroy a dog engagement transmission in no time!”

The cost is substantial, but just like the powerplant, transmissions must be reinforced to hold everything together. PPG has introduced a 1-4 dog engagement set for K-series transmissions some time ago and has helped some of the fastest teams go even faster and do it more reliably. They offer several different configurations from just adding a first and second gear set to a full five-speed gearset. PPG offers race-proven sets that feature superior heat-treating techniques, high-quality materials, and technologically advanced processes for producing their gears. For HT alumni Jason Su of Suja 1 Motoring, a 1-4 gearset fit the bill perfectly. Gearspeed has had a history with PPG products, at times under the radar building transmissions for teams to gain that competitive edge. So it was natural for Jason to send the transmission to Gearspeed, which took us through the process of installation, and supplied a stock ’02–’04 RSX Type-S K-series transmission to serve as a visual comparison between the two.

Gearspeed’s meticulously laid-out workstation where the new gearset will be installed by one of its technicians.

The Pfitzner first to fourth straight-cut dog/drag set with optional fifth case brace included. The brace is designed to add extra strength to the input and output shafts for high-horsepower, heavy-duty applications.

Since the original gears and synchros would not be returning, these are the only factory components that would be reinstalled onto the transmission once the Pfitzner set is positioned in place.

When we arrived, Gearspeed already had the K-series transmission disassembled completely and all that remained was the bare casing.

Senior Builder Jason Wishmeyer drops in the Driveshaft Shop spool with OEM 4.39 final gear and new bearings installed. It is important to always check your differential clearance without the gear stacks installed to ensure you get a true reading. This is a very important step that is often overlooked and can lead to a serious transmission failure.

After finalizing differential clearance, drop in the countershaft. Here is the PPG first gear with needle bearing and the 1-2 selector being installed. Take note of the large dog teeth that replace the failure-prone synchro assembly.

The 1-2 selector and PPG first gear with needle bearing installed.

With the third and fourth gear installed on countershaft, as well as the 1-2 shift fork, we move on to the mainshaft. The first and second gears are built onto the mainshaft along with the reverse gear, which is right above first gear. The third gear and inner needle bearing is now dropped down on the mainshaft.

This case brace is designed to keep the shafts from going astray under high horsepower loads and possibly damaging the transmission casing. This is a definite necessity for high-powered drag cars.

Jason lightly taps the mainshaft top bearing. It’s important to be precise to avoid damaging the bearing. Make sure the bearing is square before tapping it down, and don’t tap the outer bearing. Notice in place of the fifth gear selector sleeve, PPG has developed a large spacer to help guide the fork in addition to the top and bottom fork inlets.

The top countershaft bolt is left-hand threaded, and needs to be torqued down to 87 lb-ft. It is recommended to use a new one when freshening up a K-series transmission.

Torque the reverse shift fork assembly bolts to 11 lb-ft. It’s very important not to overtighten these bolts and damage the threads or snap the bolt heads. The reverse lock cam will also be torqued to 11 lb-ft.

The reverse sensor switch requires Hondabond and should be torqued down to 22 lb-ft.

Apply Hondabond to the clutch housing of the K-series transmission before the main case is reinstalled.

Jason drops the main case back in place, making sure to align everything before bolting the two sections together.

Wishmeyer uses a mallet to lightly tap the main transmission housing back in place. The moving parts within the EP3 transmission need that extra tap before the two cases will realign.

Once aligned, bolts will be used to seal the gearbox and hold everything together.

Application of the Hondabond was necessary before reinstallation of the shift lever assembly.

Reinstalling the shift lever assembly onto the main housing. Jason snugs down the shift change lever assembly bolts before torquing them to 9 lb-ft. Also be sure to apply a layer of Hondabond to the threads of the interlock bolt (Allen head).

The K-series transmission after being reassembled, sealed, and now fitted with dog box gearing.

A side-by-side comparison of the two K-series transmissions. On the left is a five-speed EP3 transmission now equipped with the Pfitzner four-speed dog gearset, and on the right is a stock ’02–’04 RSX Type-S transmission.

The backside of the two transmissions. You can clearly tell the differences between the straight-cut gears as opposed to the angled teeth of the OEM RSX transmission.

Specs

4.39 final drive ratio 1st gear : 3.000 2nd gear : 1.917 3rd gear : 1.333 4th gear : 1.045

• All bearings and seals replaced.
• Internal parts run through Gearspeed’s deburring machine (tumbler) with proprietary polishing media to reduce friction and allow for smoother operation.