Service Manual

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Two Stage Snowthrower Drive Systems Manual 1 - 9

Auger Gearbox Service

Failure Analysis

There are some misconceptions regarding these

gearboxes that result in incorrectly identifying the

causes of failure.

The square cut ring on the impeller shaft is not really a

seal. It is a wiper ring that has a tendency to pull down

to the shaft when the shaft begins to turn. The bushing

next to the ring really deflects most of the oil that is

thrown towards that area. The loose fit provides a vent

for the case (Figure 27). Occasionally a drop or two of

oil will get between the bushing and ring. When the

auger drive is disengaged, the ring will relax and that

oil might drip into the auger housing. At this rate, the

machine can be used for several years without any

significant oil loss. The yearly oil level check is more

than adequate to compensate for this.

Figure 27

2773-061

If there is a significant amount of oil coming out of this

area, it would indicate that the gearbox has been at a

severe operating angle or the bushing is badly worn.

Oil on the bottom of the gearbox can result from a leak

at any part of the case. As there is no internal pressure,

any leaking oil runs down the side of the case and

collects on the bottom until there is enough to drip off.

The source of the oil leak oil can be difficult to see.

Sprinkling some powder on the outside of the gearbox

will usually show the oil trail. The type of powder used

is not important. Just something that will stick to the oil.

When you open a gearbox that has had the gears fail,

the remaining oil will likely appear as a small puddle of

very thick grease in the bottom. Worm gears normally

create a large amount of friction due to the sliding

action. When something goes wrong, not enough oil,

poor quality oil, a problem with the gears, or just a gear

or bearing wearing out, the friction becomes

abnormally high. The remaining oil is cooked down to a

very thick residue. This can be the result of failures, not

the cause.

GEARBOX ASSEMBLY

1. Use a wire brush or sandpaper to clean the auger

shaft. A clean, smooth shaft will help avoid

damage when installing new bushings and seals.

Clean the old gasket material from the case

mating surfaces (Figure 28).

Figure 28

2773-067

2. If new bushings are to be installed in the gear

case halves, now is the time. Apply a thin coat of

Loctite™ Blue #242 or equivalent to the OUTSIDE

of the bushing and press in flush with the INSIDE

of the case (Figure 29). This will allow space for

the seal on the outside. Wipe up any Loctite™ that

is visible. The Loctite™ must not get into the gear

or seal area.

Figure 29

MVC-710

per r