Specifications

300 SERIES MAN HOLE DIGGER
FORM GOM12070702, VERSION 1.2
41
Other major components are equally shared between
all 300 Series Hole Diggers, including operator
handles, throttle control, transmission case and
bearings.
A pressure relief valve, PN 5677, is located on the top
surface of the transmission cover to relieve any excess
pressure created in the transmission due to heat rise.
Should this valve become plugged, the following
problems can occur:
1) The final driveshaft oil seal can push out of its
housing, causing a loss of transmission oil.
2) The gasket that separates the two sections of the
transmission can push out, causing a loss of
transmission oil.
The potential for these problems can be minimized by
cleaning the pressure relief valve at regular intervals.
Oil leakage between the final driveshaft and the oil seal
is the result of the following problems:
1) The oil seal is worn due to extended operation.
2) The inner sealing lip of the oil seal is cut or nicked
due to the admission of foreign material or some sharp,
abrasive object.
3) A replacement oil seal was incorrectly installed in the
transmission.
In all cases, a replacement oil seal must be correctly
installed to prevent loss of transmission oil. The oil
seal, a NATIONAL® PN 471820, is an industry
interchange standard and can usually be obtained from
local supply sources to help reduce downtime.
TRANSMISSION OIL SEAL REMOVAL AND
INSTALLATION.
Application: All 300 Series models.
Tools Required:
1 each, small, adjustable wrench
2 each, 1/2 inch wrenches
1 each, torque wrench, 600 inch pounds (68 N.m.)
capacity with 1/2 inch and 15/16 inch sockets
or
1 each, torque wrench, 840 inch pounds (95 N.m.)
capacity with 1/2 inch and 1-7/16 inch sockets
1 each, 1/2 inch drive socket wrench with 15/16 inch
socket
or
1 each, 1/2 inch drive socket wrench with 1-7/16 inch
socket
1 each, plastic hammer
1 each, three jaw gear puller
1 each, shop press
Parts Required:
1 each, PN 310-0101 transmission gasket
1 each, PN 471820 National® oil seal or industry
equivalent
1 each, PN 15 alloy Woodruff key (if required)
1 each, PN 330H-0330 final driveshaft (for Model
330H,
if required)
1 each, PN 343H-0330 final driveshaft (for Model
343H, if required)
1 each, PN 357H-0330 final driveshaft (for Model
357H, if required)
2 each, PN 08125 bearing cones (if required)
1 each, container of Barium or Lithium based,
lubricating grease
1 each, container of bearing & shaft locking grade,
anaerobic adhesive/sealant
1 each, container of wheel bearing grease
1, each, PN 999-11, transmission and engine oil or
equivalent.
1) The repair of the Hole Digger will require a level
working platform of sufficient size and appropriate
height. As an alternative, the transmission driveshaft
assembly can be securely mounted in a suitable bench
vise.
2) Drain the fuel from the fuel tank and the remaining
oil from the transmission. Refer to the Service section
for more detailed information.
GASOLINE IS AN EXTREMELY FLAMMABLE
FUE L. U SE E XT RE ME C A UT IO N W HE N
HANDLING GASOLINE. DO NOT SMOKE OR
BRING FIRE OR FLAME NEAR THE FUEL.
3) Using the plastic hammer, split and separate the
transmission cover and case. Exercise caution not to
damage the alignment dowel pins. Place the engine
and transmission cover assembly in an upright position
in a suitable area. Do not damage the throttle cable.
Remove the primary gear and pinion gear assembly.
4) Clean the transmission case with an appropriate
solvent.