gearbox FIAT 500 1961 1.G User Guide

FIG 6:7 Differential components
Key toFig 6:7 1 Axle shafts 2 Sleeve retainment lockrings 3 Slip joint casings 4 Axle shaft-to-wheel shaft
coupling sleeve 5 Differential case cover w i t h bearing inner race 6 Side gears 7 Oil boot retainment cover
8 Side gear thrust ring 9 Idle pinion shaft 10 Idle pinions 11 Oil boots 12 Differential case w i t h bearing inner race
13 Adjuster retainment ring 14 Bearing housings with retaining nuts and outer races 15 Idle pinion shaft retainment cup
1 6 Bevel gear
withdraw the layshaft together w i t h the final drive
pinion and the roller bearing inner race from the rear.
11 From the inside of the gearbox casing carefully slide off
the following parts from the mainshaft, the drive
pinion adjustment shim, the third and fourth driven
speed gears together with their bushes, the t hird- and
fourth-speed hub and sliding sleeve, the first and
reverse driven gear, and carefully drive out the front
bearings and the bevel pinion rear bearing outer race.
1 2 Using a suitable press, drive out the drive pinion roller
bearing inner race from the end of the mainshaft.
Inspection of components:
Before inspecting the various parts removed from the
gearbox casing thoroughly wash all components and
blow dry using a compressed air jet and then proceed as
follows:
1 Thoroughly inspect the gearbox casing to ensure that it
is not cracked and that the bearing seats are neither
F50069 worn or damaged so allowing the bearing outer ring
to rotate during the normal operation.
2 Thoroughly check the ballbearings to ensure that they
are in perfect condition and that both radial ply and
axial play is not excessive. The maximum permissible
bearing play is as follows:
Front bearings of primary shaft layshaft:
(a) Sideways .002 inch
(b) Endwise .017 inch
Primary shaft rear bearing:
(a) Sideways .002 inch
(b) Endwise .016 inch
Hold the bearings firmly by the outer race and gently
rock the inner race backwards and forwards. The sliding
action produced should be free and silent. If any rough-
ness is felt then the bearings must be renewed. Check
the roller bearings by inspecting the condition of the
rollers as well as the outer and inner races. Always fit
new bearings if there is any doubt as to their efficiency.

3 Check the layshaft and the primary shaft between
centres and using a dial gauge ensure that there is no
distortion. The out of true reading for bearing seats
should be less than .0008 inch. Inspect the splines and
ensure that the side and outerfaces are not indented.
Replace if there are signs of wear. Also inspect the
reverse shaft to ensure that it is perfectly smooth and
not showing signs of pitting or partial seizure.
4 Carefully inspect all gear teeth for signs of excessive
wear or damage. The contact faces must be smooth and
show no signs of indentation marks. Also check that
the backlash between the gears, when correctly
mounted on the surface plate is not greater than .0039
inch. The maximum wear limit is .0079 inch. Check that
the quick engagement front teeth of the second-, third-
and fourth-speed gears are not damaged or excessively
worn. Renew if there are signs of gearchange lever
misuse.
5 Inspect the sliding sleeves and the relevent hubs, ensure
that all the working surfaces are perfectly smooth. The
clearance between the mating parts should not be
greater than .0059 inch. Also inspect the meshing teeth
and ensure that they are in good condition.
6 Check that the gear shifting selector forks are not dis-
torted and that the striker rods freely slide in their seats
in the gearbox casing.
7 Carefully inspect that all the oil seals are in perfect con-
dition and if there is any doubt they should be renewed.
8 Inspect the striker rod locking balls and the safety rollers
and ensure that they slide freely in their seatings. Also
check the ball load spring efficiency and if this shows
signs of weakness then it should be renewed. Any
faults with these items will cause difficulty in engaging
gears or autodisengagement during engine acceleration.
6 : 4 Reassembly—gearbox
To reassemble the components to the gearbox ensure
that all components are thoroughly clean and then pro-
ceed as follows:
1 Press t h e pinion rear roller bearing onto the layshaft.
Install the layshaft in the casing, and at the same time
fit the adjustment shim, the fourth-speed driven gear
together w i t h its bush, the sleeve and hub for third and
fourth gear engagement, the first-speed and reverse
driven gear and the third-speed driven gear with its
hub.
2 Install the front layshaft ballbearing securing the
bearing retainment plate w i t h the screws and finally
lock the screws in position.
3 Insert the primary shaft together with the first, third
and fourth driving gear train in the gearbox housing
and slide t h e rear bearing onto the shaft. Push the
input shaft forward to enable the clutch shaft coupling
to be inserted in t h e rear and to be pulled up the
primary shaft by means of the pin. Do not forget the
retaining ring.
4 Slide the primary shaft backwards so pushing the rear
bearing into its bore. Refit the front bearing onto the
primary shaft.
5 On the layshaft insert the second-speed driven shaft
and bush, the second gear sliding dog sleeve and the
hub. Also insert the second-speed striker rod and the
first-speed fork. Do not forget to fit the safety roller
into its seating.
70
6 Slide the second-speed driving gear onto the primary
shaft. Place the engagement fork on the third- and
fourth-speed engagement sliding sleeve, and insert
the striker rod, lock the relevent fork and fit the safety
roller.
7 Insert the third safety roller and install the reverse shaft
and insert the reverse gear cluster onto it and secure
the shaft by tightening its block bolt. Install the reverse
striker rod w i t h its relevent fork.
8 Now refit the speedometer drive worm gear onto the
layshraft. Tighten the nuts on the primary shaft and the
layshaft, not forgetting to interpose the plain washer
between the speedometer driving worm and the nut,
to a torque wrench setting of 1 8.1 Ib ft to 25.3 Ib ft
(primary shaft) and 28.9 to 36.2 Ib ft (layshaft). It is
recommended that the input shaft and layshaft are
locked together by engaging t w o gears at the same
time. Finally, fit the splitpins.
9 Lock the shifter forks onto their shafts by tightening
their respective bolts and bend up the special locking
plates. Install the three positioning balls and relevant
springs into their bores and refit the cover plate.
10 Install the casing cover together with its relevant
gasket. This will enable correct positioning of the shift
shaft lever so that it engages in the outer ends of the
shifter shafts protruding from the gearbox casing.
11 Install the speedometer drive support on the gearbox
casing and refit the upper gearbox cover.
For subsequent differential operations and adjustments
see Sections 6:6.
6:5 Dismantling—differential and final drive
For the removal of the differential and final drive unit
from the gearbox refer to Section 6:3. To dismantle the
differential assembly
proceed as follows:
1 Remove the retaining ring 2 (see FIG 6 : 7) retaining
the splined sleeve 4 and slide the sleeve off the drive
shaft.
2 Remove t h e retaining covers 7 and the oil boots all
together with the bushes and seals, adjuster ring lock
rings 13, adjuster rings housing 14, and bearing
adjuster and roller bearing outer races.
3 Separate the differential housing halves by unscrewing
and removing the six bolts that keep both the halves and
the crownwheel together. It is advisable to mark the
respective components to ensure correct matching
upon reassembly.
4 Remove the differential pinion shaft retainer ring, also
the differential pinions 10 by removing the shaft and
withdrawing the two axle shafts 1.
5 Remove the differential side gears 6 and relevent thrust
rings 8.
6 Using a press remove the differential bearing inner
races from their seats on the carrier halves.
7 Thoroughly clean all parts and dry using a compressed
air jet.
Inspection:
The components of the differential unit must be
thoroughly inspected for correct operation and to deter-
mine the presence of any wear, damage or other irregulari-
ties. To check the items concerned proceed as follows:
1 Check thoroughly the idle pinion carrier shaft for signs

of wear, distorting or unevenness of the surfaces as this
part is very heavily pressed when the vehicle is negotia-
ting a corner. If the clearance to the idle pinions exceeds
.0059 inch the shaft must be renewed.
2 Inspect the ring gear and pinion seat, the side gears.and
the idle pinions for correct meshing. This will be shown
up by white marks on the sides of the gear teeth. Check
that none of the teeth are broken, chipped or exces-
sively worn and if any part is suspect then it must be
renewed not forgetting that the ring gear and pinion
come as a matched pair.
3 Inspect the condition of the ball and roller bearings, the
rollers and balls and working faces must not show signs
of pitting wear or cracking and if any part is suspect then
the race must be renewed.
4 Check that there is not any undue wear on the faces of
the thrust rings. Any slight indentations may be evened
out using a fine oil stone but if the damage is excessive
then new rings or oversize rings must befitted as neces-
sary. Thrust rings are supplied as service spares in the
following thicknesses.
Standard .0394 inch
Oversize .0512-.0591 inch
6:6 Reassembly—differential unit
To reassemble the differential case proceed as follows:
1 Press onto the differential half housing which carries
the ring gear one differential bearing inner race ensuring
that it is pushed fully home onto its seating. Install the
thrust ring and side gear (see FIG 6 : 7).
2 From t h e inside of the case insert the axle shaft com-
plete with pivot and runners that form the slip joint.
Also install the idle pinions and carrier shaft. Position
the ring gear onto the housing half and install the
differential pinion shaft retainer ring.
3 Press the other differential bearing inner race onto its
seating on the left differential housing half and replace
the left axle shaft complete with slip joint.
4 J o i n the t w o case halves together and tighten the
retaining screws and also the retaining screws of the
ring gear to a torque wrench setting of 23.1 Ib ft. Secure
all screws by bending up the lockplates.
5 Press t h e differential bearing outer races into their
seatings in the bearing housings and also f i t the o i l seals.
Also install the bearing housings over the driving shafts
together with the adjuster rings.
6 Install the differential unit assembly into the final drive
housing front half and bolt the rear
half onto it. Tighten
the six mounting nuts to a torque wrench setting of
27.5 Ib ft. Finally place the bearing housings in their
seats and tighten the mounting nuts to a torque wrench
setting of 13 lb ft.
It should be noted that after the gearbox has been over-
hauled the complete differential unit should only be in-
stalled after the drive pinion depth adjustments has been
carried out.
6 : 7 Final drive gear set adjustment
The installation and adjustment of the final drive gear
set requires special care otherwise the unit may have to be
dismantled again for further adjustment. So as to establish
the correct mesh of the t w o gears, their relative position is
accurately set during initial assembly at the factory.
F50071 Refer to FIG 6 :8 where it will be seen that t w o numbers
are stamped on the pinion shaft near to the threaded end,
the upper number is the matching number which should
also appear on the crownwheel. The lower number indi-
cates the positive or negative deviation from the theoretical
distance between the centre line of the ring gear and the
pinion face. It is this number which must be taken into
account when calculating the adjusting shim thickness
which has to be fitted between the rear roller bearing and
the fourth-speed gear on the layshaft.
The formula from which the adjusting shim thickness
can be calculated is as follows:
S=A—(B + C)
Where S=shim thickness.
A= distance between the front bearing inner
race and the centre line of the ring gear.
B = distance of the drive pinion face to the ring
gear centre line.
C = t h e total of the widths of the third-speed
gear bush, third- and fourth-speed hub,
fourth-speed gear bush and rear roller
bearing inner race fitted onto the mainshaft
It should be noted that 'A' is the total of half the diameter
of the differential bearing housing seat which is in actual
fact 41.00 mm, and the distance measured between the
front bearing inner race and the differential bearing housing
seat. The last
dimension will have a minimum manufactu-
ring limit of 150.54 mm. Any deviation from this value
must be determined and considered when determining
the total shim thickness 'S'.
A= 150.54 + 41.00 + a (deviation)
To determine deviation 'a' Fiat tool A.62036 should be
assembled to the gearbox casing as shown in FIG 6 : 9
and to take the reading proceed as follows:
1 Assemble the front ballbearing and its retainer into the
gearbox housing and tighten the retainer bolts.
2 Hold the gearbox housing in the vertical position with
the differential side upwards and insert Fiat tool
A.62036 carefully from above into the bearing bore and
lock it firmly by tightening the knurled nut.
3 Using Fiat dial gauge C.689 which has been previously
zeroed on a surface plate should next be mounted
onto the t o p of Fiat tool A.62036 with its pointer resting
on the lowest position of the differential bearing hous-
ing bore as shown in FIG 6:10. To obtain the lowest
point move the pointer to both sides of the bottom dead
centre position so as to obtain the maximum reading.
The distance ' B ' in the formula for calculating the shim
thickness is designed to have a lower manufacturing limit
of 75 mm. Any deviation ' b ' is stamped on the drive pinion.
Therefore to calculate the value of ' B '
B = 7 5 + b (deviation)
The distance 'C' in the formula for calculating the shim
thickness is designed to have a lower manufacturing limit
FIG 6 : 8 Layshaft w i t h final drive pinion. The arrow
points to the number (14) for correct mating with ring
gear and to the centesimal figure (—10) for accurate
mating position of pinion and gear

TOOL A 62039
TOOLA. 62040 PIN WRENCH A. 52022
FIG 6:15 Adjusting ring gear-to-pinion backlash and
differential bearing play, using special wrench A.52022
reading on the dial gauge should be between .0031 to
.0047 inch. The actual clearance is adjusted by
screwing in one adjusting nut and screwing out the
other by the equivalent amount using Fiat spanner
A.52022 as shown in FIG 6:15.
4 Remove Fiat tool A.62041 and using Fiat support
A.62040 mount the special dynamometer A.95697 and
adaptor on the axle shaft. Rotate the axle shaft several
turns so seating the bearings and then check using
the dynamometer the rotation torque.
5 If necessary tighten or slacken the adjusters until the
specified torque of 1.01 ± .07 lb ft is obtained. This
operation must be very carefully carried out because if
one adjuster is set differently with respect to the other,
a variation in ring gear to pinion backlash may take
place, resulting in a variation of rotation torque. After
any adjustments always recheck on the ring gear to
pinion backlash and if necessary readjust and then
repeat the rotation torque check.
6 Finally check the tooth contact between the pinion
and ring gear as detailed in the following instructions:
Check and adjustment of tooth contact between
pinion and ring gear:
1 Carefully apply to the ring gear teeth a thin layer of
engineers' blue and gently rotate the differential whilst
holding the axle shaft firmly but allowing them to slip
slightly so as to have the unit working under load
conditions.
2 A contact impression will be left on the ring gear teeth
and the contact will be correct when the drive pinion
tooth contact pattern is evenly distributed on the ring
gear teeth as shown in FIG 6:16. Should the tooth
contact be incorrect the following observations should
be noted.
Excessive contact on tooth flank. Too deep
meshing — move pinion out from ring gear by reducing
thickness of shim.
Excessive contact on tooth heel. Too slight
meshing—move pinion in towards ring gear by
increasing thickness of shim.
74
6 : 8 Replacement of gearbox—differential unit
Installation is the reverse procedure to removal of the
unit from the vehicle as described in Section 6:2.
However, the following points should be noted:
1 Ensure that the clutch driven disc hub is correctly
aligned with the clutch shaft pilot bush.
2 The complete transmission unit should be carefully
pushed towards the engine and the clutch shaft
inserted into the driven disc hub splines and finally
home into the pilot bush. Extreme care must be taken
to ensure that no weight is placed on the clutch shaft
otherwise distortion may take place.
3 Carefully connect the gearbox rear housing to the
engine crankcase by using the studs, t w o of which
have special location dowels fitted. Screw home
finger tight the gearbox/differential to body to front
support mounting screws inserting the fibre washers.
Lower the hydraulic garage jack and pull it away from
underneath the vehicle. Screw in the four lower
mounting nuts and tighten to a torque wrench setting
of between 18.1 to 21.7 Ib f t.Finally tighten the front
support screws.
4 Reconnect the gear shift control rod and the speedo-
meter drive cable. Insert the springs between the axle
shafts and wheel drive shaft and tighten the
three
mounting screws of each splined sleeve on the
flexible joint to a torque wrench setting of 20.3 Ib ft.
5 Refit the flywheel housing cover. Replace the starter
motor together with its relevant cover and tighten the
two mounting nuts to a torque wrench setting of
18.1 to 21.7 Ib ft. Reconnect the starter control rod,
the t w o starter cables, the clutch control tie rod and
hook up the return spring and secure the clutch
control cable retainer bracket to the gearbox casings.
Reconnect the cable to the battery positive terminal
post
6 Lower the vehicle to the floor gently and then give a
thorough road testing.
6 :9 Swing axle shafts and slip joints
Description:
The t w o axle shafts are connected to the differential
unit through specially designed slip joints which allow
the shafts to swing and slide in the splined housing in
the differential side gear. At the other end, the axle shafts
are connected to the wheel drive shaft flexible joints
using a sliding sleeve. Excessive contact on tooth face. Too slight
meshing—move pinion in towards ring gear by in-
creasing thickness of shim.
Excessive contact of tooth toe. Too deep meshing
—move pinion out from ring gear by reducing thickness
of shim.
With all the above detailed cases, to adjust the pinion
by replacing the shim, the differential unit and drive
pinion shaft must be dismantled. This means that when
the unit is reassembled after the necessary adjustments
have been made, the backlash and bearing rotation
torque must be repeated.

CHAPTER 9
THE STEERING SYSTEM
9 : 5 Relay lever and support
9 : 6 Steering rods
9 : 7 Front wheel toe-in
9 : 8 Fault diagnosis 9:1 Description
9 : 2 Steering wheel removal and refitting
9 : 3 Steering box removal and refitting
9 : 4 Steering box dismantling and reassembly
9:1 Description
The steering gear fitted to the new 500 range of
vehicles is of the worm screw and sector type with a
steering ratio of 1:13. The steering gearbox is located on
the front lefthand side of the dash wall on the scuttle as
shown in FIG 9:1. The steering gear comprises a pitman
arm and relay lever pivoting on a pin supported on the
body. A central track rod connects the pitman arm to the
relay lever. T w o track rods connect the pitman arm and
relay lever to the knuckle arms.
9:2 Steering wheel removal and refitting
To remove the steering wheel proceed as follows:
1 Disconnect the battery positive terminal clamp and
remove the horn control from the steering wheel.
2 Remove the cable from the push button seating and the
cable insulation sleeve.
3 Using a suitably sized box spanner or Fiat wrench
A.8279 unscrew the steering wheel to shaft nut as
shown in FIG 9:2.
4 Using the palm of the hands against the back of the
steering wheel rim gently tap the steering wheel
forwards so releasing it from the inner shaft.
F50097 5 Reassembly is the reverse procedure to dismantling.
Care should be taken to ensure that the front wheels
are located in the straight ahead position when the
steering wheel is being replaced otherwise the steering
wheel spokes will not be correctly positioned.
9 : 3 Steering box removal and refitting
To remove the steering box from the vehicle proceed
as follows:
1 From inside the vehicle remove the steering column
clamp bolt 6 (see FIG 9 : 3) after flattening the lock-
washer 7.
2 From the underside of the vehicle remove the t w o
tie rod locking nuts from the pitman arm and then using
Fiat tool A.46006 or a suitable t w o leg puller withdraw
the pins from the seats.
3 Remove the three nuts holding the steering box to the
body panel. Ease out the worm screw from the
steering shaft and lift away the steering box.
4 To refit the steering box is the reverse procedure to
dismantling. The steering box to body mounting nuts
should be tightened to a torque wrench setting of
14 Ib/ft to 18 Ib/ft.

(h) Starter motor rough or noisy
1 Mounting bolts loose
2 Damaged pinion or flywheel gear teeth
( i ) Lamps inoperative or erratic
1 Battery low, bulbs burned out
2 Faulty earthing of lamps or battery
3 Lighting switch faulty, loose or broken wiring
connections
F500
125
(j) Wiper motor sluggish, taking high current
1 Faulty armature
2 Bearings out of alignment
3 Commutator dirty or short-circuited
(k) Wiper motor operates but does not drive
arms
1 Gearbox components worn