Again, to save time and effort, I collected a re-conditioned gearbox and
overdrive unit from MGB Hive at the same time as the engine (I understand the
gearbox & overdrive weigh about 50Kg). New gearbox mountings were fitted
and the NG gearbox crossmember (supplied with the chassis) was attached.
Before mating the gearbox to the engine, the new clutch parts had to be fitted.
The release bearing was first fitted to the release fork and then this assembly
fitted inside the gearbox bell-housing with a new dust cover.
I had purchased new overdrive isolator and reverse switches (these are
identical) which were screwed into their positions on the top of the gearbox.
The overdrive isolator's function is to prevent the overdrive unit being
energised unless 3rd or 4th gear is selected (i.e. the gear lever must be in
the right hand side of the selection "H"). The reverse switch's
function is to pass current to the reversing light when reverse gear is
selected. These switches are "adjusted" for depth using fibre washers
as packing so I used a multi-meter to help determine the best depth.
The prop shaft was dismantled, cleaned and reconditioned with new universal
joints. These joints are best fitted with the aid of a vice to carefully press
the cups into the yokes. All joints were then thoroughly greased with a grease
gun and the gearbox was filled with about 3.5 litres of 20w/50 oil.
The gear lever was
fitted after the body and dashboard were in place as some modification was
needed.
Clutch
A new clutch slave cylinder was fitted to the right hand underside of the
gearbox (see picture). A stainless flexible hose was used to connect this to
the hose union bracket on the NG chassis. From here a copper pipe was run to
the clutch master
cylinder on the footwell top.
The clutch can be a bit of a pig to bleed! Having had the same problem on my
neighbour's MGB, we discovered that a good strong purge is wanted. If using the
manual method, good heafty pushes on the pedal are needed or, if pressure
bleeding is used, a pressure of around 25 psi is desirable.