TM 5-3895-346-14
PUMP OVERHAUL
POWER STEERING
Shaft End
1. VTM27 and VTM41-Support the shaft end of the pump body in a two- inch straight pipe coupling and,
using an arbor press, remove the shaft thrust spacers, outer needle bearing, and shaft seal. The shaft
assembly should drop through a slot in the press table so the shaft will not be damaged. The outer needle
bearing and shaft seal are a press-fit to the body. Use a pin punch and hammer to tap the inner needle bearing
from the body.
2. VTM28 and VTM40-Remove the shaft and seal from the pump body. The shaft bushing is included in
the body subassembly and cannot be serviced separately.
3. VTM42-Remove the large snapring that retains the outer ball bearing in the body. Press the shaft and
outer ball bearing from the body. Remove the inner, small snapring that retains the outer ball bearing and
remove bearing from shaft. The inner needle bearing and shaft seal are a press fit to the body. Use a pin
punch and hammer to tap them from the body.
INSPECTION, REPAIR, REPLACEMENT
NOTE
Wash all parts, except seals, in clear mineral solvent and lay them aside for
inspection. Replace all old seals and O-rings at reassembly.
Ring, Rotor, Vanes, Pressure Plate, Body-Inspect the surfaces of all parts which are subject to wear. Light
scoring may be removed from the faces of the body or wear plate with crocus cloth (by placing the cloth on a
flat surface), medium India stone or by lapping. Check the edges of vanes for wear. Vanes must not have
excessive play in slots or burrs on edges. Re- place if necessary. Check each rotor slot for sticky vanes or
wear. Vanes should drop in rotor slots by their own weight when both slot and vane are dry.
Relief Valve-Insert valve in its bore in pump cover. There should be no binding. Check valves and bore for
excessive wear and scoring. Replace if necessary.
Bearings-Wash bearings and shaft assembly thoroughly. Bearings must be replaced (VTM27, VTM41, and
VTM42 only) if they are removed for any reason. The shaft bushing cannot be serviced on VTM28 and VTM40
Pumps. If the bushing becomes worn, replacement of the body subassembly must be made.
Shaft and Seal-Replace the shaft seal at each overhaul to prevent oil leak- age. Check the drive shaft oil seal
diameter for wear and scoring. Do not install a new seal on a shaft which is worn or damaged at the oil seal
diameter. Replace the shaft if worn. Stone and polish the sharp edges on the shaft to prevent damage to the
seal.
Body and Cover-Stone all mating surfaces with a medium India stone to remove all burrs and sharp edges.
Rewash all parts after stoning.
REASSEMBLY
NOTE
Immerse all parts in clean hydraulic oil to facilitate reassembly.
Shaft End
1. VTM27 and VTM41 Pumps-Press inner needle bearing in the body, using an arbor press.
2. Assemble the split-ring thrust spacer on the shouldered portion of the shaft and install shaft in the
pump body.
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