The Build – Part 1 – Differentials

The first part of the B44.3 build will be the differentials; 3 gear diffs to be exact. Since we’ll be working with grease and fluids, it’s a good idea to have some rags available to clean up any messes you WILL make.

The manual has you adding 4 .5mm shims to the outdrives; 2 inside and 2 outside. Adding 4 shims will make it VERY difficult to get the roll pin installed internally, so we have to play with the shimming. The bad news is you won’t know until AFTER you have the diff built. So, I’ve built the diff so that it works for me, but your shimming might be slightly different. As a side note, try to keep MORE shims inside than out.

Step 1 - We just received these cool mats from CowRC.com. These mats are based on a large, magnetic mat that has foam separators for different ‘pockets’ to hold parts in. It’s best to have a clean work space and this mat will be great for this.

Step 2 - We’re going to prep all the outdrives up front. First, slide a small red o-ring onto the outdrive and into the first groove. Next, slide ONE .5mm shim onto the outdrive followed by a larger, red o-ring. Prep all 6 outdrives.

Step 3 - Squeeze some black grease onto the outdrive as shown, coating both red o-rings. Now slide the outdrive assembly into the metal diff gear. Build 2 of these.

Step 4 - Follow the same procedure as you did in Step 3 but this time insert it into the diff housing. Build 2 of these.

Step 5 - Add 2 shims to the outdrive. Do this on both assemblies.

Step 6 - Adds 2 shims to the diff housing side as well. An easy way to get these installed is to slide them on the shaft of a hex wrench, place the tip of the wrench on the outdrive and let the shims slide right down.

Step 7 - Insert the roll pin into the hole in the outdrive and key the large sun gear to it. You can add a little dab of black grease to the sun gear to keep it in place.

Step 8 - Build four of these smaller sun gear assemblies; each shaft should have two sun gears (facing each other) and two small shims.

Step 9 - Place one sun gear assembly into the gear housing, keying it to the grooves. The first one in should have the cut in the shaft facing up; the second one placed should have the cut in the shaft facing down. Build 2 of these.

Step 10 - Fill the differentials with 5000wt fluid up to the top of the sun gears. Let them sit for a few seconds to let the oil settle into the cracks and refill if necessary.

Step 11 - Place the diff gaskets into place as shown. You can add a dab of black grease to keep them in place.

Step 12 - Combine the 2 diff halves and screw together. Rotate the diff a few times in both directions to make sure all the gears have meshed correctly.

Step 13 - Slide 3 shims onto the outdrives followed by a 3/8? bearing. We might have to adjust the shimming of these in a later build.

Step 14 - Follow the same procedure to build the center diff as you did for the front/rear diff; grease the o-rings, slide them into the diff halves and add the shims, pins and sun gears.

Step 15 - Build the sun gear assemblies, install them and add the 60,000wt fluid. Add the gasket to the other side, using grease to keep it in place if it moves at all.

Step 16 - Screw the two halves together.

Step 17 - Flip the center diff assembly over and attach the spur gear to it.

There we go. All 3 diffs done and, hopefully, build properly!

Part 2 – Assembling the gearboxes.