Are your gears grinding? Have you noticed a recent decrease in performance? Or has it gotten so bad that the truck doesn’t even move anymore? We’ve all been there. Usually we get so caught up with flinging our rides over the biggest gnarliest jumps we can find that we neglect to think of all the abuse we’re throw at the transmission. These things aren’t usually sealed so if you’re running through sand, water, or mud you’ve likely got a gearbox full of crud and needs serious attention. In our case however we noticed a slight clicking sound on a new Traxxas Stampede when jumping large obstacles. If you’re in a similar boat or haven’t touched the gearbox in the last millennia then this article is for you.
The following is a quick how to article on the proper way to remove, clean, and reassemble your radio controlled truck’s gearbox. The truck pictured is a Traxxas Stampede XL-5 but since every model will be different this article doesn’t get into depth on the exact locations of screws and such that need to be removed. Instead this is meant to give you a general idea of the steps involved.
Pictured below is the motor and transmission on our Stampede. It is setup like most “stadium” style trucks with the motor sitting as far back as possible. Usually with this sort of setup the motor turns a pinion gear which drives a spur gear. Coupling the spur gear to the transmission is a slipper clutch. The slipper clutch is meant as a means to dampen the torque of the motor from the transmission gears under hard acceleration and heavy landings. We’re getting ahead of ourselves though because before we can get to all of that we first need to remove the truck’s rear tires, pinion/spur gear cover, and then the motor itself.
Pictured below is what you’ll see when you remove the rear wheels. The arrow (A) points toward the drive pin. Be very careful that you don’t let it fall out onto your living room carpet otherwise you’ll be searching forever. Don’t ask me how I know.
In the image below you can see the pinion/spur gear cover after it’s removed. Immediately after removing the cover we found the culprit (B) to our woes. A small pebble was stuck inside there and when we would hit a hard landing it would vibrate around and hit the gears. Luckily it didn’t damage the teeth on either
Here is what the smaller pinion, and larger spur gears look like with the cover removed. Your next step will be to remove the motor but first you’ll need to remove the pinion gear which is held in place with a tiny allen head screw. The large black thing on the spur gear is the slipper clutch unit we spoke about above.
Here’s a picture of the gearbox from the other side with the motor removed. Check out all the garbage that was stuck under the motor.
Here is the gearbox removed. Again we won’t go into much detail as to how to remove it from the truck because that will vary greatly from truck to truck. However we can tell you that it’s quite easy and usually consists of removing a few screws from underneath the chassis which hold the gearbox in place. Then you’ll need to remove the drive axles, and a few other small bits to get it out.
Pictured below is the transmission removed and disassembled. Because our truck was so new the inside of our gearbox was impeccable. However you’ll likely need to remove each gear and clean and inspect it for wear or damage. Missing or rounded over teeth are the usual problems. If you find either then it’s time to replace the part in question. We were pleasantly surprised to find that the Traxxas already had bearings installed. However if your truck is equipped with plastic bushings this is the perfect time to goto the local hobby shop for some bearings. As for inspecting bearings try rolling them in your fingers. If they feel gritty it’s time for a replacement. Most hobby shops stock individual bears so you won’t have to buy an entire set. After cleaning all the gears and inside of the box it’s time to lightly lubricate each gear and bearings and reassemble. Remember that excess grease on the gears will cause a decrease in efficiency which will result in decreased battery life and a slower vehicle. BTW our vehicle came equipped with a gear differential. If however yours has a ball diff this is the time to disassemble it and replace parts as needed.
After everything is back in the truck the final thing you’ll need to do is to set the mesh between the pinion and spur gears. Some people can do this by eye, but if you’re new to this sort of thing I suggest trying the old paper trick. It consists of taking a small strip of ordinary paper and sliding it between the gears. Then push the gears together and tighten up the motor screws to hold it in place. When you remove the paper your gear mesh should be set just right. Want to make sure? Hold the pinion gear still (usually the motor will do this for you) and lightly rock the spur gear back and forth. You should just be able to see a little wiggle room between the gears. If there is absolutely no wiggle room then it’s set too tight. If there is so much wiggle room that it looks like the gears could slip then it’s too loose.
Overall removing and maintaining your gearbox is really easy and can save you money in the long run.