Traxxas T-Maxx Forward Only Conversion

The following procedure will help you complete one of the more popular T-Maxx modifications, removing the reverse gear and servo from the truck in order to improve overall throttle response, speed, and weight.

This shows the conversion on an original style t-maxx, steps 1,2 and 17 will vary for the 2.5 T-Maxx due to servo and linkage configuration.

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Much of this information is a modification of this document: http://www.traxxas.com/products/nitro/tmaxx/blueprints/tmaxxforwardonly.pdf

Part numbers where applicable have been included for reference from your manual.

Step 1 – Get Your Parts - Traxxas TRX 4994X Forward Only Conversion Kit. I got mine on Ebay for $10, online or from Traxxas it’s about the same price. There are other kits out there, this one seems to work just fine and is from Traxxas.
Step 2 – Remove the Servos, Receiver, Battery Box, and throttle servo rear mount – This makes it easier to get the transmission out, and will make it easier to get the truck cleaned up. Plus, you won’t need your gearshift servo any more anyway, so remove it from the receiver. You’ll also have to disconnect the throttle and brake linkages. Just remove the brake linkage at the servo so it’s easier to reconnect, then pull the throttle linkage up out of the way. The shift and brake linkages will still be attached to the transmission at this time.
Step 3 – Turn the truck over to access the transmission screws. If you’re using any type of skid plate over this area (ie: RPM kit), remove it and set it aside. There are 8 screws, which are found in the middle of each chassis brace. Remove the screws from the transmission. The screws will likely remain in the chassis brace and the transmission will “fall out” as all of the screws are loosened – Make sure to catch it! Carefully slide the rear of the transmission downward, allowing the rear drive shaft (yoke) to disconnect from the transmission (output yoke). At the same time, slide the front of the transmission downward, allowing the forward drive shaft (yoke) to disconnect from the transmission (output yoke). You have now removed the transmission from the truck.
Step 4 – Clean the transmission. Since you’ll be opening the case, now is a great time to scrub down the transmission case to make sure you don’t get any grease and grime into the transmission case. A little soap and water and a scrub brush works great. Make sure to completely dry the case before proceeding.
Step 5 – Remove the set screw pin and the output yoke (part 4927) from the transmission and set it aside.
Step 6 – Rotate the disc brake so that the yoke set screw faces down. Push the disc back to allow access to the set screw. Remove the set screw. Remove the yoke (part 4927), hex brake adapter (part 4966) and disc brake (part 4964) and set them aside.
Step 7 – Remove the seven screws on the transmission case and set aside.
Step 8 – Carefully pull the front half (the side with the spur gear) of the transmission off.
Step 9 – Remove the two-speed drive assembly and set it aside (keep the assembly together.)
Step 10 – Remove the ball screw from the shift-fork shaft (part 4989). Remove the forward/reverse output shaft assembly (part 4994) along with the shift fork shaft. Put these somewhere to store, they will not be used once the kit is installed.
Step 11 – Using a pair of needle nosed pliers and allen wrench, remove the idler gear assembly (part 4996). This assembly is made up of a nut and bolt. Loosen the nut until the bolt comes free. NOTE: don’t forget to remove the race that the bolt slides through (see exploded parts views). You can remove this with the pliers or if you forget, it will fall out when you put the screw in during step 12.
Step 12 – Replace the shift fork shaft seal (where the gear shift mechanism went into the transmission) with the included 5x6 roundhead machine screw. Use a 4x6 roundhead screw to plug the idler gear hole.
Step 13 – Install the forward only shaft (part 4994x) replacing the forward/reverse output shaft assembly. Install the longer end of the output shaft towards the disk brake side of the transmission. Install the two-speed assembly.
Step 14 – Reassemble the transmission case, disc brake assembly, output yoke and drive shaft connections and set screws.
Step 15 – Reconnect the forward drive shaft, sliding it into the output yoke in the transmission. Reconnect the rear drive shaft, sliding it into the output yoke in the transmission.
Step 16 – With the truck upside down, align the 8 screws and transmission holes, and carefully screw them tightly down one at a time, beginning with the four outer screws, and then moving in a circle inward until all are tight.
Step 17 – Reinstall the throttle/brake servo, receiver and battery boxes, and steering servos. Reconnect all linkages and test for adjustments.
Step 18 – Take it out and HAVE FUN!