Overhauling Brakes on a Weasel
Submitted by - Gary P. Szechy
Revision Date 5/1/01

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This service is required to restore proper steering and braking operation of the M29 Studebaker Weasel. If you find yourself having to put your shoulder or even your entire body into the steering of your vehicle, you are well overdue for this overhaul.

Step one is to gain access to the drive train tunnel by removing the sheet metal center flooring section. Remove the drive shaft, the 3 linkage rods at the differential, the speedometer cable and the rear exhaust pipe. Remove both rear axles by unscrewing the six bolts and "pulling" the axle using the two "jack screws" by unlocking their lock nut and turning in, (clockwise). Mark each axle "LH" and "RH" for proper re-assembly.

Next, check to see if you have a drain plug on the rear housing, (after serial # 3449). Without a drain hole in the sheet metal hull, these drain plugs are relatively useless as there is not enough room in the well to get a reservoir large enough to accept 6 quarts of oil. (we will deal with this issue later). You will also notice that there is a drain plug in the bottom of the forward 2-speed transmission section of the differential. If you have a hand siphon pump, siphon as much oil out of the fill hole as possible.

Next, dump 10-20 lbs of oil dry, (kitty litter works just fine), into the rear hull section around and under the differential, Make sure your drain plugs in the outer hull (drivers side) are in place or you will leak oil on your garage floor. If missing, just use NPT pipe plugs. Pull all differential drain plugs or unbolt the 14 bolts that secure the differential carrier assembly to start the oil draining process.

Next, stand back and collect your thoughts on the huge mess taking place and question yourself, "why did I start this?"

If you haven't removed all the case bolts yet, now is the time. The carrier assembly is now free for removal. Using an engine hoist or chain-fall, secure the carrier assembly for removal with a 1" nylon lifting strap or length of chain etc. I found that looping the strap around both brake cam arms was the ideal balance point of the assembly. It is a good idea to stabilize the unit at the companion flange, (U-joint flange) to prevent rotation of the unit while hoisting.

Depending on your lifting arrangement, you may have to remove the muffler shield for clearance. At this point, observe if you have a differential gasket or simply silicone adhesive. If you have a gasket, take a micrometer measurement of the thickness. I had what looked like a factory gasket installed and it measured .015"-.020 inch. With an incorrect thickness gasket, the concentricity of the carrier drive gears and the axle tubes will be out of alignment. This will have an effect on the free-roll of the vehicle and also possibly the removal and assembly of the axles. CarQuest auto parts sells gasket sheeting .0156" thick, (1/64"). It is stocked as part number JV100 and comes in a 18" x 36" roll for under $2.00 USD.

Take some shop rags, paper towels etc and remove the oil that is residing inside the axle tubes. There is a flared cone inside the axle tubes that prevents an excess amount of oil loss into the tubes when the vehicle travels across inclined slopes. Therefore, a rag can only be pushed through from the outside inward. At this point we need to start cleaning up our mess. Re-distribute the oil dry or kitty litter to absorb the drained oil. Use plenty of oil dry as we will vacuum up this mess with a shop vacuum.

Once all the oil dry is vacuumed up, spray down the hull floor, differential and axle tubes, (inside and out) with engine degreaser. To do the job right, you will probably need 4-6 cans. After this sits awhile, rinse the areas with a pressure washer and hot water until no oil remains. This may take several cycles, each time vacuuming the wastewater out of the hull with a shop vacuum.

Now is a good time to "engineer" a drain plug system so next time you change your oil, you won't have to go through this mess. By the way, what kind of oil was in the differential? It probably was 80 or 90 wt. hypoid gear lube, which is the wrong lubricant. Once the rebuild is completed, you will need to install 6 quarts of non-detergent SAE 30 wt. engine oil. Back to the oil plug, from the inside of the differential housing drill a'pilot hole through the cast iron completely through the floor pan. Center this hole 1" behind the casting seam that is visible from the inside of the unit.

Using a 1" hole saw with a pilot drill, drill a hole through the sheet metal floor pan from the bottom of the vehicle using the previously drilled pilot hole. Make sure that you use safety glasses and try not to hit the differential case when you break through the sheet metal. Next, use a 7/16" drill bit and open up the pilot hole in the differential case. This 7/16" hole is the proper tap drill for a -18 NPT tap plug fitting. Next use a two handed tap wrench, plenty of oil and tap the hole from the bottom to accept a NPT drain plug. Purchase the drain plug prior to tapping as you will need it to gauge your tapping depth. Remember that these are tapered threads and the deeper you tap, the farther the drain plug will engage. If you go too far, you will loose the sealing properties of the interference fit. Tap the hole a little at a time until you have two threads visible on the mating plug after the plug is tightened into the threaded hole. You will need to fabricate a "cover plate" to seal the hole from dirt and debris, or water if you are floating a M29C.

Next, lets move on to the carrier assembly that was removed from the vehicle. The first step is to clean it up. If the wrong oil was use, you may have a sludgy mess which all needs to be cleaned off prior to teardown. Find a suitable catch basin and position under the hoisted assembly. Purchase a couple of gallons of kerosene and using a siphon/blow gun and an air hose, degrease the entire unit thoroughly.

Do not use engine degreaser and water rinse as you will destroy all your bearings as the rusting action will begin rapidly. As a final rinse, mix some non-detergent motor oil into the kerosene and spray down to prevent any oxidation.

Next, we need to take a good look at the bearing caps and the side bearing caps for identification. If the unit was depot ordnance serviced, there should be some punch marks stamped to identify location for proper re-assembly.
This is extremely important as the bearing caps are line-bored as an assembly and the side caps and mating shims will control proper pinion to ring gear spacing.

Look on one side, (caps and side caps) being marked with one prick punch and the other side marked with two prick punch marks.

If you have metal punches, it would be a good time to stamp "L" and "R" on these components. Stamp the bearing caps and the housing where they join so that you don't mistake assembly by 180 degrees. Also stamp the side caps for the same reason.

Now it is time to take the unit apart. A detailed R&R of this procedure is covered in TM9-1772.

Remove both braking cams and remove the large brake band adjusting wing nuts and cork seals. Next, remove the four bolts and side bearing cap from the left side and remove the shims from the top of the bearing cone. Put a tag and wire around these shims and mark them "LEFT". Do the same for the other side. It is extremely important that you do not mix up the shims as they control the pinion to ring gear clearance and backlash.

Now you can remove the bearing caps and the carrier assemble should be free enough to remove the bearing cones. Again, label and tag each bearing cone "LEFT" and "RIGHT" as their proper reassembly is critical.

To remove the carrier assembly, we need to free up the brake band adjustment rods that pilot through the housing. A drift is needed to tap these through while pulling free the carrier. This is a two-man operation and the assembly should be resting on some plywood to prevent damage to the components. If you are installing NOS bands, don't worry about bending the bands during disassembly. If you are re-lining the bands, try not to distort them more than you have to. They are dead soft steel and can be reformed against the brake drums later if they do get distorted.

Once the carrier is free, we need to remove the brake drums. These will be secured by a light press fit of the bearing races. On my unit, one was removed by hand and the other was not so easy. If you have a puller, now is the time to use it. If not, you can take an old wood chisel and grind it to a very gradual taper and tap it between the race and the flange. Alternate from side to side and it should come free. Again, tag and label the races to their respective bearings for proper reassembly.

Inspect the drums for wear. If they have grooves in them, replace them. At the time of this writing, NOS drums were available from TJ Murray for $50.00 each. If the there are minor grooves, the drums can be lathe turned. Drum OD should fall between 10.964" and 10.994".

While the bearings and shims are out, rinse them in a suitable cleaner and blow them out with compressed air.

Replace all the cork seals with O-rings. Make sure you buy these at an auto parts store and they are oil/gas resistant. O-rings purchased at a plumbing/hardware store are suitable for use with water only and will swell and fail when exposed to oil. I was able to find suitable O-rings for the lower band adjusting screws and the brake cam levers.

For the two" ID seals used on each brake band adjusting rod, I used cut washers made from" ID neoprene rubber fuel line. These seated well against the conical sealing face that is machined in the housing.

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