Rebuilding an MTD snowblower auger differential

February 7, 2011

This auger, on a 1995 MTD Yard Machine snowblower, hit a heavy electrical cable, hidden under a foot of snow. It immediately broke the differential gears without shearing the shear bolts. For those who like to tackle their own repairs, here is how I did it. The parts cost $170.

You will be working on equipment that has sharp edges, gasoline in the tank, and a spark plug. Appropriate personal protection equipment should be used and the spark plug wire should be removed from the plug.


Remove the three nuts on each side of the auger housing which hold the housing to the main body of the snowblower. The nuts have been removed and the welded studs are seen to the left of the V belts. Pull the auger housing away about three inches and unhook the tensioning spring.


Remove the spring. Note that the open end of the spring is facing the motor.


Prop up the snowblower body.


Remove the plastic chute from the auger housing, noting the position of any steel reinforcing plate under the chute. Remove the center bolt of the pulley. It will probably be necessary to put a block of wood into the impellor to hold the pulley stationary while breaking the bolt free. Remove both pulleys.


The bearing securement plate is held in position by three bolts and nuts. There are three holes in the impeller to access the bolt heads. The nuts face the motor. Remove the bolts and nuts and the plate. Alternately, you can leave the bearing in place and when you withdraw the complete auger assembly, the shaft will pull through the bearing. I removed the bearing for inspection.


Note the position of the bearing. It just sets in there and is held in place by the bearing plate.


Looking in the housing from the front, mark the augers left and right and the outside position. Remove the three bolts and nuts on each side of the assembly. The bolt heads are on the outside of the housing. Pull the auger assembly forward. The rear shaft will pull through the bearing if you�re lucky. Otherwise some penetrating oil and gentle persuasion with a hammer may be necessary.


Note the parts positions on the outward end of the auger assembly: Large bushing in the steel cup, shim, and then small bushing in the end of the auger.


Note the small bushing and two shims on the inward end of the auger assembly.


Remove the two roll pins that secure the impeller only if that shaft is to be replaced. Use a file on the area where the sheer pins pass through the auger shaft so as not to damage the rubber oil seals when removing them. Remove the bolts that hold the two halves of the differential together. This differential has no gasket between the halves and is glue-bonded together. Use a sharp chisel carefully to pry the halves apart.


This unit hit an electrical cable hidden under the snow. In the case on the right side, you can see all the brass shavings in the grease.


The brass gear took a good hit. The worm gear was damaged and the key elongated the shaft slot. Replacement parts are $170 for both shafts and brass gear and a few incidentals.


Note the position of the parts. From the left is the bronze bushing and two shims. A new roll pin is pressed in.


The key is put into the shaft keyway. There is one shim on each side of the brass gear. The gear is centered over the key. The shafts have been greased so as not to damage the seals which are slid all the way along the shaft. The seal�s lips face inward towards the grease. The solid side of the seal with the numbers, faces outward to the environment.


Assembled differential.


One case half is coated with a light coating of Permatex silicone sealer and the differential is bolted back together. I torqued the bolts to about 7 foot pounds. Note the black plug on the top of the differential. This is where you add the lube. Good luck. I filled the case with an appropriate amount of OO Snapper-type grease. Some other brand's cases use Lubriplate lithium grease. I made a device to force grease through a thin hose using low air pressure.


Reassemble the augers again, noting the position of the shims and bushing.


Note the position of the bushings and shim.


Instead of using the roll pins to secure the impeller, I used two sheer pins. Install the new sheer pins in the augers and use your previous markings to properly assemble them. The shaft goes through the rear of the auger housing. Secure both ends of the auger shaft to the auger housing using bolts and nuts.


The shaft is not seen here because I installed the bearing first. Push the bearing onto the shaft. Alternately, you can loosely install the bearing assembly first, insert the finished auger assembly, and tighten the bolts and nuts once the shaft is passed through the bearing.


If you haven't yet done this step, you can now install the bearing plate. The shaft will self-center the bearing. Once you are sure the bearing is centered, tighten the nuts. The bolt heads can be held in place through the three holes in the impeller


Install both pulleys and I torqued the bolt to 30 foot pounds, not having a reference chart.


Place the completed auger housing close to the snowblower body and reinstall the spring with the open end facing the engine.


Position the belts on the bottom of the pulleys and attach the housing to the body with six nuts. Make the final adjustments and you�re done.

Comments (10)

  • ericwi

    Not too much rust for a 15 year old snowblower. Great photos!

  • baymee

    That's the main reason the unit was saved. Another reason was the continuing snow days and nothing available at the big boxes.

  • jim109


  • tomplum

    Outstanding as usual baymee!

  • baymee

    You could have sold that snowblower this weekend! Along with any generator, battery, and kerosene heater.

    Just got electric back after 2 1/2 days, which is a record outage here. Electric had been so reliable until the last few years. Now a generator is almost a must.

    The tree damage is just unbelievable. They were breaking and falling all around this whole area. You'd hear the branches breaking in the forest every second during the storm.

  • Chuck104

    The rear bearing is frozen to the impeller(splined)shaft.
    I tried spraying with WD-40 and placed a wood block across the impeller shaft end and hit it hard with a hammer but the impeller shaft would not slide through the bearing. Any suggestions on how to remove the rear bearing would be appreciated.

  • redoctobyr

    Chuck104, you might want to try some PB Blaster penetrating oil. I was also reading recently that some people are making a good penetrating oil out of a 50/50 mix of acetone (such as nail polish remover) and automatic transmission fluid. That could also be worth a shot. Let them soak in for a while, and try again? If you have access to something like a 3-jaw gear puller, or something else that will let you try to crank it off by turning a screw, that could also help out. I'm assuming you were able to remove the bearing & shaft from the auger housing. If not, then disregard the gear puller comment. If it came to that, you could also try heating the bearing, while trying to avoid adding heat to the shaft. The bearing might expand away from the shaft by enough to help get it off. But the heat would cook the grease in the bearing, and maybe destroy it. So I'd use that as a last resort, since you may really be committed to replacing the bearing if you try heating it. Again, if it is out of the machine, and the bearing is exposed, you could also cut it with something like an angle grinder (either one slice through it, or cut it in half), and get it off that way.

    baymee, that's a great writeup! I have a 1993 MTD. And mine, despite being stored indoors, has noticeably more rust than yours, so kudos! When I bought mine in ~'02, the impeller would turn, but the augers wouldn't. Both shear pins were intact. Drove out the shear pins (both of them were bent, but had not broken), and opened the auger gearbox. In my case, the gears were all fine (fortunately), it had just sheared off the woodruff key that prevents the brass gear from spinning on the auger shaft. About $.70 later I was back in business. I always thought that was very lucky, but I never appreciated quite how lucky until reading this. Why mine simply sheared the key, and yours shattered the gears, I have no idea. I'm glad you got it fixed, though, nice job!

  • bghoenowcontests

    I have a 2003 yardworks blower which looks virtually identical. For about a year the unit would throw,chew auger belts. Tried tension adjustment, new belts, etc to no success. Only yesterday when I took the auger housing completely apart did I realize that the two auger pulleys are not aligned with the motor pulley. I am presently at the point of picture #4 above. My question if anyone can be of do I determine which part needs repair/replacement. I can't tell what is causing the "whoopsie" in my pulleys that is causing my belts to be thrown. Is it the actual pulleys....the self aligning bearings, the shaft? How can I determine this? Thanks!

  • baymee

    The 3 nuts/bolts that you see may be loose, but if I remember, the bearing has to be aligned before final tightening of the bolts.

  • mcmurray

    Excellent job. Great photos. Thank you very much. Your time and post is greatly appreciated.

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