Rock Monster 6.4:1 Transfer Case Gears
with Bill Johnston

Going from stock transfer case gears to something lower can be as easy or as hard as you want to make it. You can get a 'kit' from an aftermarket manufacturer/distributor that includes gears, seals and bearings or you can just buy a complete case to swap out. The decision is easy to make, because if you have a Factory Service Manual (also available from an aftermarket manufacturer/distributor), the proper tools and the mechanical knowledge, you will save some money. But if you want to just bolt in the goods and go wheeling you can do that to.

But first things first. So you want to figure out what gears you have without pulling splitting the case? If you are not the first owner of your Zook, then here is how you can tell what you have without taking the previous owners word for it. Here is an easy way to check them out. This can be done with the case still in the vehicle, but as long as we were swapping out components we thought we would show you a clearer picture with the case on a stand.

Click through for a closer look...Click through for a closer look...If the case is still in the vehicle you can put the rear axle on jack stands or just remove the driveshaft from the rear output flange so it will turn while parked. We have added some small arrows to the flanges to show the start and finish points a little easier. You can see the front output flange that connects the case to the front axle the lower left side of the picture. The Flange on the upper right portion of the picture is the input flange that connects the case to the transmission (through the jack shaft). Both flange arrows are pointing straight up, and your goal is to make one full revolution on the output flange (lower left). Turn the input flange clockwise and count the revolutions. The stock transfer case ratio for 4Low is 2.268:1 so you can see that after two revolutions the flange still has to go a little more than a quarter turn to bring the output flange arrow back to the 'straight up' position.
Click through for a closer look...Click through for a closer look...Checking out the new case we are installing shows that the input flange must rotate about 4/10ths past the sixth rotation to bring the output flange back to center. This shows that we got just what we ordered. This case is equipped with the new Trail Tough 6.4:1 Rock Monster Gears. These are one piece gears made by the makers of the original Suzuki gears from Japan. 
Click through for a closer look...Click through for a closer look...When ordering the complete Trail Tough case, you still need to move a couple of items over from the old case. Here you can see where we moved the 4WD light sensor from one case to the other. Also note that Trail Tough ships their case with a plastic plug that has to be removed before you can install the sensor. This plug not only keeps foreign material out of the case, but it also keeps the ball bearing in place so it doesn't get lost in shipping. 
Click through for a closer look...Click through for a closer look...Also notice that in these pictures you see a shifter handle in each case. The newly rebuilt case does not come with one, you must transfer your shifter from the stock case. We put an extra shifter in place to make it easier to shift into gear for this demonstration.  
On the street, the transfer case gears didn't make any sound that we could hear. They were nice and quiet. On the trail we only heard the gears when we were in 4Low at high RPM. But that sound is normal. Overall performance - Awesome! Trail photos will be coming soon.

Trail Tough Products
1031 Narregan St
Medford, OR   97501
1-877-SUZUKIS (789-8547)

08/22/22 14:05:03


Disclaimer: The fabrication, modifications and designs you see on this web site are personal experience.  If you duplicate these modifications you do so at your own risk. These articles were written over many years of that hands-on experience. The companies offering these components may no longer have them on the market. Please use these articles to keep the hobby alive.


Suzuki, Samurai, Sidekick, Vitara, Grand Vitara, X-90, and the Suzuki "S" Logo are all registered trademarks of American Suzuki Motor Corporation. Geo, Chevy, and Tracker are all registered trademarks of General Motors Corporation. This site is in no way endorsed by or affiliated with the American Suzuki Motor Corporation or General Motors Corporation.