Section C (24/12/08 )

GEARBOX

C.1    To remove gearbox from car
C.2    Dismantling
C.3    Reassembly
fig. C.1    Gearbox assembly
fig. C.2    Dismantling the Gearbox
fig. C.3    Lay and reverse gear shaft breakdowns
fig. C.4    Primary and main shaft breakdowns
fig. C.5    Special bearing extractor
fig. C.6    Tool and gauges

 

Sabra Handbook Plate 8

Cl

REMOVAL FROM CAR

Acces to the gearbox for checking and topping-up oil level is from beneath the car.  Removal of the front tunnel by withdrawing side screws can aid servicing and inspection.  For repair or overhaul of the gearbox, however, it is necessary to remove it from the car, and this is accomplished as follows.

  1. Drain gearbox of oil, preferably when hot, by removal of drain plug.  Take out the side (level and filling) plug to aid flow.

  2. Remove tunnel front and rear covers, from inside the car by withdrawing the fillet "Phillips"  screws and lift clear.

  3. Disconnect gearbox from bell housing, after chocking-up rear of engine to support weight.

  4. Free Propeller Shaft rear end by removing the four bolts from the rear universal joint.  This permits the propeller shaft to be lifted at the rear and withdrawn rearwards.

  5. Remove Transverse Mounting Bolt  from the bush mounting beneath the end of the rear cover.

  6. Disconnect Speedometer Cable by unscrewing the knurled barrel at the right hand side of the box rearcover.

  7. Lift Gearbox Upwards and Rearwards, clearing rear mounting with minimum of lift to avoid undue strain on the engine water hoses, choke and control cables, linkages etc. and when free from the bell housing, allow rear of engine to settle gently on to support chocks.  The gearbox should then be free to lift on to bench.  The use of suitable wooden cradles will assist all work on the bench. 

 

C2 Sabra Handbook Gearbox Pic 02

 

C2

DISMANTLING THE GEARBOX

  1. Remove Top Cover
    Unscrew the nine bolts securing the top cover and lift clear complete with gear lever, taking care not to damage the cork seal.

    To Dismantle Top Cover

    1. The gear lever is removed by depressing the base cap, and an anti-clockwise turn will free its bayonet retention.

    2. The three shift rails are freed by the removal of their retaining grub screws.

    3. All shifting and selector fork castings are secured to the shift rails by grub screws wich are unscrewed to dismantle.

  2. Remove Gear Cover
    Remove the six retaining nuts and draw clear of the fixing studs in the rear of the gearbox housing.  Remove the sealing gasket intact.

    To Dismantle Rear cover

    • The speedometer drive bush is freed from its socket at the right hand side of the cover by removing the grub screw.  It will withdraw completely with its helical gear and spindle.

    • The rear cap is withdrawn to remove the dus proof radial seal ring.

    • An internal white-metal bush supports the driven end of the propeller shaft and this is renewed by shrinking in a replacement.  It is not normally removed.

  3. Remove Reverse Lever, reverse Gear and shaft
    Free lock washer, and remove the bolt with two flats located on the side of the gear case.  The reverse gear and shaft should then lift out.

    To Dismantle Geverse Gear
    Remove, in this order, the spring clip, thrust washer, needle bearing and the 17 toothed sliding gear with end thrust washer.

  4. Remove Primary Shaft
    See that a flat on N)1 synchro gear lies parallel to the top of the case, to ensure clearance of the laygear.
    Use a thin, flat brass drift applied to bear on the primary shaft flange to drive the complete assembly forwards.  Care should be taken to avoid jarring the needle bearing or this may fall out of the gear housing.

    To dismantle Primary Shaft
    Remove spring retaining clip, shim and split washer to free the ball bearing.  The gear and shaft are integral, with the gear end face bored to house the needle bearing.

  5. Remove Reverse Gear from Mainshaft

    This is the cluster projecting to the rear of the gearbox housing, formerly within the gear cover.

    Remove the spring clip from immediately behind the helical speedometer driving gear.
    The speedometer gear, collar, reverse gear, shim-housing and bearing retainer with shims will all come off rearwards over the tail of the shaft.
    Fig C.3

    Sabra Handbook Gearbox Pic 03

  6. Remove Mainshaft and Rear Bearing

    Expand and free the large rear bearing retaining clip from its seat in the periphery of the bearing agains the rear face of the gearbox housing.
    To extract the rear bearing, which is a press-fit in the gear case housing, it is essential tu use the special bearing extractor (see fig C4)
    Before removing the bearing, first remover the 12 toothed reverse gear from the rear end of the layshaft, where it projects through the rear of the gear case (below and to the right of the mainshaft), by removal of the retaining clip.
    This is necessary to make room for the head of the bearing extractor tool, which is then engaged in the peripheral bearing groove from which the retaining clip has just been removed.
    The two valves of the extractor tool are then locked to the bearing by means of the outer sleeve, which holds them together.
    The threaded screw at the other end of the tool is brought to bear on the end of the shaft, and progressive tightening by the hand-toggle will cause the bearing to be drawn rearwards, and freed.
    If difficulty is experienced in engaging the tool head in the bearing, it may be necessary to use a soft drift to tap the shaft rearwards from its other end, to shift the bearing and its groove out until the tool can engage.
    The mainshaft, complete with main cluster, will now lift from the box by careful manoeuvring, and the tail of the mainshaft, drawn forwards and upwards will follow.

    To Dismantle Mainshaft

    1. The front cluster is removed in the following sequence; first speed thrust-washer and first speed gear, needle race from within the first gear, thrust washer, first and second speed synchro mechanism.
      Lift the flat locking key from its keyway, remove the thrust washer and the second speed gear with its split needle race.  This completes dismantling as far as the shaft flange.

    2. The rear bearing having been removed (6-above) there remain only the third and fourth speed synchro mechanisme, the third gear thrust washer and locking key.  This completes dismantling of the rear cluster.

    To dismantle Synchro Bodies

    The parts separate easily.  Take care not to lose the spring-loaded balls from within the assemblies.
    Fig C.4Sabra Handbook Gearbox Pic 04

  7. Remove Layshaft
    The external spring clip and reverse gear have already been removed (6-above).  Now push the layshaft to the rear and remove the roller bearing from outside the gear case.
    The shaft should then move forward and upward to lift clear of the box, complete with gears and front bearing.

    To Dismantle Layshaft

    1. Remove the inner half of the rear thrust bearing

    2. Remove the front bearing

    3. Remove, in sequence, the spring clip, fourth gear, second spring clip, third gear.  The first and second gears are integral with the shaft. (Note that fourth and third gears are a shrunken fit and should be heated to not more than 158F (70C) to facilitate removal.

 

 

C3

REASSEMBLY OF THE GEARBOX

The sequence given should be followed inGearbox conjunction with the check-points, gauge tensions and tolerances quoted.

  1. Refit the Layshaft - reverse order to the dismantling procedures

  2. Refit the Mainshaft - Similarly

  3. Refit the Primary Shaft - Similarly

  4. Refit the Reverse Lever
    See that the radius on the top half of the lever is towards the lever securing bolt, and refit with the lock washer.
    (The lower adjusting screw, which sould have remained correctly set, must bear on the lever when this is pushed against the reverse shaft).

  5. Refit the Gearbox to the car - Reverse to the removal instructions

    Reassembly Check Points

    1. See that the rounded nose of each gear is facint in the direction of the mesh.

    2. Check shaft end-float and other tolerances given below.

    3. Heat leyshaft gear on hotplate within limits stated.

    4. Check synchro body tensions carefully with the gauge made to Dwg. P86490 (See fig C5)

    5. It is important, when fitting the first and second synchro body to see that the locking device is on the second gear and NOT in the first gear.  The function of the ZF-Synchro-lock is based on the principle that the parts to be coupled must have obtained equal rotational speed before they can be smoothly engaged.  During the procedure of gear changing the axial sliding of the sliding sleeve on the synchronizing body must therefore be held back by the locking device until the parts to be engaged have obtained aqual rotational speed.  Not until the contact surfaces, which are pressed together at the instant of changing gear, have caused the parts on the engien side to turn at the same speed as the parts on the vehicle side, can the locking device be pressed back by the persistetn pressure from the sloping inner theeth of the sliding sleeve to their original position.
      Wit the lock released the sliding sleeve can move in the direction of the gear.  Direct connection between driving shaft and main shaft is only effected in fourth gear.  (It should be understood that when the synchro body comes into contact sith the gear it rotates the synchro mechanism, and only when the speeds are dynchronized is ite possible to change gear).  Not that there is synchro locking on second, third and fourth gear, NOT on first gear.

     

Fitting Tolerances

The following figures should be used for checking gear assemblies.
First and second speed synchro mechanism tension should be checked with gauge P 86490 at 14-15 kg (31-33lb)
Third and fourth speed synchro mechanism tension should be checked with gauge P 86490 at 13-14 kg (29-31lb)
Clearance between synchro bodies and gears 7-9 mm (0,273-0,351 in).
Clearance on all gears (end float) 0-2 mm (0,000-0,078 in)
Clearance between synchro ring and selector forks 1-3 mm (0,039-0,117 in)
Clearance between race an gears 0,01-0,012 mm (0,004-0,005 in).
Clearance between speedometer drive and bush 2 mm (0,078 in).
Clearance between gear lever and selector fork 2-3 mm (0,078-0,117 in).
Clearance between rear bush and propeller shaft 1 mm (0,039 in).
Clearance between gears (back lash) 0,002-0,003 mm (0,001-0,0015 in).

Fitting Tools

The three special tools are as follows:

Extractor Fig C5, used to remove rear mainshaft bearing.
Tool Fig C.6 used to replace rear mainshaft bearing.
Gauge Fig C.
used to check and set synchro pressures.

 

Fig C.5
Sabra Handbook Gearbox Pic 05

Fif C.5
Fig C.6

Sabra Handbook pic 06

Common Technics