DRESSTA TD-25M EXTRA, Service Manual

Page: 192 / 595

SECTION 7C
TRANSMISSION
Page 74
TD-25M EXTRA DRESSTA
CHARGE AND SCAVENGE PUMP
26. INSPECTION AND REPAIR
1. Discard all seals, O-rings and wear plates and replace with new ones during reassembly.
2. Wash all parts thoroughly in a suitable solvent. Dry thoroughly with compressed air.
3. Check all parts of pump separately with the following suggestions.
A. Gear Housing
Wear in excess of 0.13 [mm] cut-out necessitates
replacement of the gear housing.
Place a straight-edge across bore. If you can slip a 0.13 [mm]
feeler gage under the straight-edge in the cut-out area,
replace the gear housing.
Pressure pushes the gears against the housing on the low
pressure side. As the hubs and bearings wear, the cut-out
becomes more pronounced. Excessive cut-out in a short
period of time indicates excessive oil contamination. Withdraw
oil sample and check it and main frame for dirt.
Where cut-out is moderate, 0.13 [mm] or less, gear housing is
in good condition, and both ports are of the same size,
housing may be flopped over and reused.
B. Gears
Any wear on gear hubs detectable by touch, or in excess of
0.05 [mm] necessitates replacement. Nicking, grooving,
fretting of teeth surfaces or head discoloration also
necessitates replacement. Scoring, grooving or burring of
outside diameter of teeth generally means replacement is
necessary unless damage is light and can be stoned off.
NOTE: Gears assemblies must be replaced in pairs .
C. Wear plates
The wear plates seal the gear section at the sides of the
gears. Wear here will allow internal slippage, that is, oil will
bypass with in the pump. 0.05 [mm] maximum wear is
allowable. Replace wear plates if they are scored, eroded,
pitted or discolored. Check center of wear plates where the
gears mesh. Erosion here indicates oil contamination. Pitted
wear plates indicate cavitation or oil aeration. Discolored wear
plates indicate overheating, probably insufficient oil.