The Build – Part 3
Part 3 of this build revolves around the transmission of the T4.2. This is one of the best transmissions out there and is extremely easy to build.
Build Notes:
Take your time building the differential. This is one of the most important parts to build right as it help provide grip for the rear of the T4.2. It’s also an involved process to remove and fix if you don’t do it right the first time.
You will be working with greases and lubes in this step so it’s a good idea to have some clean towels or rags handy.
The first thing we need to do is get the diff rings to stay connected to the outdrives. You can do this by applying a bit of the clear diff lube to the outdrive and then attaching the ring to it. The next step is to build the thrust bearing assembly. Start by sliding one of the diff thrust washers onto the diff thrust bolt. Apply a thin layer of black grease to that washer and carefully place the 6 thrust balls into the grease. Slide the 2nd thrust washer into place. Your assembly should look like this. You might run your finger around the outside to remove any excess grease. Press one of the 5/32 bearings into the ‘female’ diff outdrive as shown. Slowly slide your diff thrust bolt assembly up into the outdrive, making sure all the bearings stay within the diff thrust bolt assembly. Drop the 2nd 5/32 bearing into place and drop the diff gear over it. The bearing should sit flush with the gear as shown. Now fill each diff ball hole with a dab of clear diff fluid. I usually drop the balls into the gear (as shown) and roll them into the holes. The diff grease helps keep them from falling out of the assembly and onto the floor. Make sure each hole gets a diff ball. Your assembly should look like this so far. Pre-compress the diff spring with a pair of pliers. One or two full compressions should be good. Slide the opposite diff out drive into place, making sure the diff thrust assembly does not get pushes out of the ‘female’ diff side. Now drop the diff spring and locking t-nut into place. Note the orientation of the t-nut. Tighten the diff thrust assembly into the t-nut. Every 2-3 turns, ‘work’ the diff but rotating the outdrives in opposite directions. This should help seat all the internal parts. Tighten until the t-nut bottoms out, but DO NOT overtighten. For starters, loosen the diff thrust bolt approximately 1/8 of a turn. ‘Working’ the diff again, it should feel extremely smooth. If all goes well with step 36, slide the diff cover into the diff thrust side as shown. Now we’re moving on to the transmission case. Start but pressing a 10x66mm and 3/16 bearing into both sides of the case as shown. They should be somewhat snug. If they are not going in easily, do not force them. They need to go in perfectly straight for a nice, smooth transmission. Press 2 more 3/16 bearings into the idler gear. Insert the idler gear shaft into the assembly. Slide the top shaft spacer onto the top shaft as shown. Slide the top shaft into the case, followed by the idler gear assembly and finally the differential. Make sure you insert the diff with the diff thrust screw facing out of the case. This will keep the diff from loosening up while driving. Slide the opposite transmission case half into place and secure with the single 4/40×1/2 screw (for now). Do not insert the other screws yet; they’ll be a pain to deal with while we finish up this part of the assembly. Attach the motor guard to the top of the transmission case with the 2 4-40 screws. Attach the wing mounts/body mounts to the transmission with the 4-40×1 1/4 screw. Note that there is a left/right wing mounts/body mount; they are keyed to the transmission. Be sure you have them on correctly. Now you can insert the 3 4-40×1 screws into the transmission. Be sure to slide the washers on first. Place a small drop of blue thread locker onto the 4 screws that are sticking out (the 3 1″ and the wing mount/body mount screw). Line up the FT motor plate and secure with the 4 screws. Tighten down until the screws are snug; do not overtighten. Finished assembly. Make sure the wing mounts/body mounts can move slightly. We’ll need to re-position them in a later step. Pre-compress the slipper spring like we did to the diff spring in step 35. Press the octagonal pad into one side of the gear as shown. It might stay or it might not. If it doesn’t, further assembly could be a little trickier. Press one of the VTS slipper pads into the VTS slipper housing followed by the VTS slipper plate, the 2nd VTS slipper pad and then the VTS outer hub. Your assembly should look like this. Make sure the parts are all keyed together (the VTS outer hub and VTS slipper plate). Slide the FT V2 slipper hub onto the top shaft followed by the 84T spur gear (note the orientation of the gear with the slipper pad from step 50). It is extremely important that the slipper pad stays seated in the grooves of the gear during this step. Finally, slide the VTS slipper assembly onto the top shaft. Slide the slipper spring into place followed by the V2 slipper washer and 5-40 locknut. Tighten the locknut down until it holds the assembly in place, then check to make sure the rear slipper pad is still seated in the grooves of the spur gear. If everything looks good, continue tightening the 5-40 locknut down until the end is flush with the top shaft. That’s it…transmission done! Part 4 – Installing the rear suspension.
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