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Function, Construction and Operation
Drive Shaft Function
-to transmit power from one point to another in a smooth, constinuos action.
-In trucks and construction equipment,the drive
shaft is designed to send torque through an angle from
the transmission to the axle( or auxiliaryt ransmission).
-The drive shaft must operate through constantly changing relative angles the
between transmission and axle.
- it must also be capable of changing length while transmitting
torque.
- The axle of a vehicle is not attached directly
to the frame, but rides suspended by springs in an irregular,
floating motion.
Construction of a Drive Shaft
-To transmit required torque loads, the drive shaft must
be durable and strong. Forged steel and high-strengrth,
cast, end yoke for heavy-duty vehicles are used to provide
the necessary rigidity required to maintain bearing
alignment under torque loads.
-Anti-friction bearings are used to with stand oscillating
loads while the drive shaft is rotating at high speeds.
The needle roller bearings on the cross trunnions carry
large loads and are used because of their high capacity
in a limited space.
-Abrasive material is a major problem for vehicles operating
in extremely moist and dirty environments. To
Combat this problem, synthetic rubber seals were developed
and resulted in increased life, ability to with stand
high temperatures and a less critical relubrication cycle
for drive shafts.
-Special high-strength tubing is used to provide maximum
torque carrying capacrty at minimum practical weight.
Drive shafts have been developed to meet the vehicular
industry needs.
-The slidings plines betweens lip joint and permanent joint
must support the drive shaft and be capable of sliding
under full torque loads.
-To aid in this axial or slip movement,
Glidecote was developed to reduce sliding friction,
reducing thrust under hight orque.This non-metalli coating
also prevents spline galling and extends spline life.
Operation of Drive Shaft
-Each shaft is installed in the same manner. A universal joint (Cardan type) and
splined slip yoke are located at the transmission end of the shaft, where they are
held in alignment by a bushing in the transmission rear extension.
-The slip yoke permits fore and aft movement of the driveshaft as the differential
assembly moves up and down. The spline is lubricated internally by transmission
lubrication or grease. An oil seal at the transmission prevents leakage and protects
the slip yoke from dust, dirt and other harmful material .
-From some automatic transmissions, the slip yoke spline is lubricated with grease
and provided with a small vent hole.
The slip yokes should be inspected to be sure the vent hole is clear (Figure 19).
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INSPECTING END FITTINGS
Visually inspect all input and output end-fitting (yoke) retaining nuts, clips, or
bolts for any gaps between mating surfaces. If gaps are present, consult
transmission, axle or transfer case original equipment manufacturers’ service and
maintenance manuals for proper fastener specifications.
Try to move it vertically and horizontally to feel any
looseness. (See photo left.) Listen for any clicking, or
grinding noise from the joint.
Take hold of the end fitting with both hands, rotate left to
right, feeling for play or backlash (see photo left.) Listen for
any clicking, or grinding noise from the joint. If radial
looseness is evident, U-joints or yokes will have to be
replaced.
. (See photo left above.) There should be less than .006 in.
(.15mm) movement in the universal joint kit relative to the
inboard or outboard yokes. If looseness is greater than .006 in.
(.15mm), the universal joint kit must be replaced.
INSPECTING UNIVERSAL JOINTS
Type
1.Relubable style
2.Permanently Lubricated Plug Style
3.Permanently Lubricated Net-Formed
Style
Reubable style
Check for the presence of all grease zerk (nipple) fittings. (See
photo left). Grease zerk (nipple) fittings should not be missing,
loose or fractured.
Permanently Lubricated Plug Style
Permanently lubricated plug style universal joint kits do not
contain grease zerk fittings, only a plug. (See photo left) Make
sure plug is not missing, loose or fractured. If the plug is loose,
tighten to required specifications.
Permanently Lubricated Net-Formed Style
Net-formed universal joints do not contain grease zerk
(nipple) fittings or plugs and are not relubable (See photo
left).
INSPECTING SLIP MEMBERS
Check the slip member assembly for excessive radial
looseness.
(See photo left) If looseness is greater than .012 in. (.30mm)
as read on dial indicator, replacement of the slip member
assembly is necessary.
For an inboard and outboard slip yoke assembly design, check
to be sure the slip yoke welch plug is not loose, missing or
damaged. (See photo left) If any of these situations are
evident, replacement of the slip yoke and professional are
balancing of the driveshaft is necessary.
Visually inspect for the presence of the grease zerk fitting, if
applicable, on the slip yoke. (See photo left) Grease zerk
fittings should not be missing, loose or fractured.
Check the slip yoke seal. (See photo left) Make sure the seal is
properly attached to the slip yoke and is not loose or damaged.
If any of these situations are evident, replacement of slip
member assembly is necessary.
For permanently lubricated slip members, check yoke shaft
boot (see photo left) or seal can. Make sure the boot or seal
can is properly attached to the yoke shaft and tube sleeve and
no damage or looseness is apparent
INSPECTING TUBING
Check the driveshaft for bent or dented tubing, cracks, or failed welds. If any of
these situations is evident, replacement of the complete driveshaft assembly or
tube is necessary.
INSPECTING CENTER BEARINGS
Visually inspect all center bearings, end-fitting midship nuts for
any gaps between the mating surfaces. (See photo left) Be sure
to repeat check for broken back and backlash.for all center
bearing end fittings.
Inspect the center bearing bracket bolts for looseness. (See
photo left) If looseness is evident, are tighten center bearing
bracket bolts. Check the alignment of the bracket before
tightening the bolts. If any of these situations are evident,
replacement of the center bearing assembly is necessary.
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