General Description; Removing The Gearbox; Dismantling The Gearbox - MG MGA Twin Cam Workshop Manual

GENERAL DESCRIPTION

The gearbox has four forward speeds and one reverse. Top gear is obtained by direct drive, third and
second by gears in constant mesh, and first and reverse by sliding spur gears.
A sliding joint of the reverse spline type is fitted to the rear end of the third motion shaft and is
lubricated from the gearbox.
F.1 REMOVING THE GEARBOX
Remove the power unit as described in Section A. 24.
Remove the starter motor, unscrew the bolts and nuts securing the bell housing and exhaust pipe
support brackets, and withdraw the gearbox and rear extension from the engine. Take care to keep
the gearbox flange parallel with the crankcase face until the first motion shaft is clear of the clutch.
F.2 DISMANTLING THE GEARBOX
Extract the dipstick, drain plug, and speedometer drive.
Unscrew the nuts and remove the gear lever remote control tower and joint washer. Remove the nut
and spring washer securing the propeller shaft driving flange and withdraw the flange. Use service tool
18G34A to hold the flange while the nut is removed.
Unscrew and remove the six bolts and the rear extension cover and joint washer.
Remove the interlock arm and bracket.
Remove the two nuts and six set screws securing the gearbox extension to the gearbox. Pull the
extension from the gearbox, at the same time manoeuvring the remote-control shaft selector lever
from the selectors.
Unscrew the three countersunk screws and the seven hexagon-headed set screws holding the
gearbox cover; remove the cover and overshoot stop.
Cut the locking wire and unscrew the three change speed fork set screws.
Unscrew the two set screws and remove the shifter shaft locating block with shifter shafts from the
gearbox; note the two dowels in the block; take care to catch the three selector balls and springs.
Withdraw the forks from the box in the following order-reverse, top and third, and first and second.
Unscrew the clutch lever pivot nut; screw out the pivot bolt and remove the lever with the thrust
bearing.
Unscrew the nuts and remove the gearbox front cover; note the bearing shims between the cover and
the bearing.
Tap out the layshaft, allowing the gear cluster to rest in the bottom of the box.
Unscrew the retaining set screw and remove the reverse shaft and gear.
Withdraw the mainshaft assembly to the rear.
Withdraw the first motion shaft complete with 18 spigot needle rollers.
Lift out the layshaft gear cluster and the two thrust washers.
Rear extension
Release the front and rear selector levers from the remote-control shaft by removing the clamping
screws and sliding the levers from the rod. Extract the keys from the shaft and withdraw the remote-
control shaft from the rear extension.
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