MTD Garden Tractors User Manual page 120

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ing turns. What about shimming? The primary
reason for shimming is to set the proper back-
lash or clearance between gears. This is espe-
cially important on bevel gears. In this case it's
the backlash between the bevel gears on the
input pinion and the drive shaft. Too much
backlash can create a noisy transmission and
too little backlash creates a tight transmission
that will wear very quickly. See Figure 5-26.
Figure 5-26.
When the transmission is manufactured a shim
of the proper thickness is used on the drive
shaft between the 10 tooth gear and the trans-
mission housing to set the proper clearance
between the input pinion bevel gear and the
bevel gear on the drive shaft. See Figure 5-27.
Figure 5-27.
Another shim is used on the input pinion shaft
and is placed between the retaining ring and
the transmission housing, setting the proper
amount of end float for the input shaft bevel
gear. See Figure 5-28.
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Figure 5-28.
Another shim is used on the input pinion shaft
and is placed between the re Thrust washers
are also used on the drive shaft, output shaft,
and axle shaft to absorb the thrust and side
loading of the gears so that they do not rub on
the aluminum transmission housing.
This transmission uses a heavy gear oil to
lubricate the moving parts. The heavy oil does
not stick to the parts as much as grease does,
helping to remove heat from the moving parts.
Important Note: Gasket Installation
1. Prior to reassembly of the transmission, make
sure that all gasket grooves in the housing
halves are clean and dry. The surrounding
perimeter must also be free of oil and other flu-
ids.
2. It is not recommended to re-use a rubber
molded gasket as it conforms to the irregulari-
ties of the casting surface. This condition will
cause a leak if the irregularities are not
matched during reassembly.
3. The gasket is designed specifically for a snug
fit and does not require sealant in the casing
groove. RTV sealant will only need to be used
where the ends of the gasket meet at the mat-
ing surfaces. It is required at the flat ends only.
Do not overuse the RTV.
4. Align the locating tabs on the gasket with the
proper locations on the casting. The ribs
should be facing up.
5. Gently push the gasket into the casing groove.
Be certain not to stretch the gasket. Stretching
will create surplus material at the end of the
groove and a poor seal may result.
5-8