The gearbox swap begins.

As summer gave way to autumn and the temperatures died down to more sensible levels, I decided to take a few weeks off of work to spend some quality time with the newest member of our family. I also agreed with the missus that I would be able to spend a few hours in the garage here and there in order to try to get the Beast up and running in time for the McLaren Vale Vintage and Classic Run (spoiler alert: I missed it – but that didn’t stop me from trying).

The existing gearbox in the car had two problems: 1) it was only the four speed non-OD and 2) it whined horribly in all but 4th gear suggesting the layshaft bearings had probably seen better days. I’d managed to source a rebuilt OD gearbox from across the Tasman which had been sitting in my garage patiently waiting to be fitted for several months – finally its time had come…

As I am not fortunate enough to own a car lift, the first step was getting the car high enough off of the ground to comfortably remove the ‘box from underneath. I have a nice set of 1000kg Stanfred ramps but raising the car on these alone would have provided, at best, the very minimum amount of space required to perform the job. To get the car up a little higher I made some improvised bases for the ramps out of landscaping sleepers and angle iron – this gave me an extra 100mm or so of space under the car which makes accessing the underside of the car a lot more comfortable.

Plenty of room underneath


I also knocked up some small platforms for the rear wheels to sit on to give me a bit more space at the rear of the car to remove the exhaust etc.

Platforms to provide extra height at the rear


It took a couple of attempts to drive the car up onto this arrangement of supports but it’s up there and it’s solid so I’m happy. It’s lovely having this amount of room to work underneath the car so once this job’s over I’ll keep my timber extension pieces for any similar tasks that come up in future.


Angle iron prevents the ramps sliding backwards or sideways


Once the car was raised to a suitable height, the job of removing the old gearbox could begin. The first step was to drain the ‘box of its fluid via the drain plug on the underside and to remove the gearlever assembly from inside the car. Next, the wiring was unplugged from the reversing light switch on the selector mechanism housing and the speedo cable removed from the side of the gearbox casing. The clevis pin holding the slave cylinder piston to the clutch release fork was removed to separate the two, the middle exhaust mounting undone and removed from the brackets attached to the gearbox and the four bolts holding the output flange to the propshaft were removed before gently lowering the prop towards the ground. At this point, to give myself more room I opted to remove the entire exhaust system from the car – a couple of the rubber mounts need replacing and the flange to manifold gasket is missing so I’ll address those when reassembly time comes. Other than that the system looks to be in great shape and is quite possibly original (the Aussie climate is great for classic cars).

Clutch slave cylinder clevis pin


Once freed from all of the ancillary parts, the next step was to lower the gearbox to gain access to the bolts attaching the bell-housing to the engine back plate. According to the workshop manual, this can be done with a trolley jack placed under the engine sump, using a block of wood to distribute the weight. As I had not undertaken this task before I opted for a belt and braces approach of using use two trolley jacks – one under the sump as per the manual and then a second underneath the rear gearbox cross-member (to be honest this wasn’t necessary and if I did the job again I would use just a single jack as per the factory recommendations).

My belt and braces lowering approach – the central axle stand was a temporary measure whilst the job was paused for lunch


After supporting the ‘box with the jacks I undid the four nuts holding the rear gearbox cross-member to the car floor pan and dropped the ‘box in stages – lowering the rear jack by about an inch first, then using the sump jack to lower the unit down onto the rear jack until the cylinder head was resting against the bulkhead.

Rear GBox Mount
Rear gearbox cross-member – attached via four nuts/bolts


After the unit had been lowered and was self-supporting against the bulkhead I completely removed the cross-member from the gearbox (actually it fell off as the rear mount had disintegrated – luckily I have a good Mackay replacement from Chris Witor) and set about removing the various bolts which secured the gearbox to the engine backplate. Most of these are relatively easy to remove, although the top three or four require the use of one or more long socket extensions and a universal joint due to their difficult-to-access positions. In all removing the bolts was probably a half-hour job. The final four bolts to be removed were the two holding the clutch slave cylinder and the starter motor to the backplate. Be prepared for the weight of the starter motor when you remove its bolts as it is a surprisingly heavy beast and your head is likely to be somewhere beneath it!

At this stage the gearbox is free to be dropped from the car. To do this I removed the cup from my large trolley jack and positioned it underneath the gearbox so that the sump plug of the ‘box was located in the resulting hole. Using the long  trolley jack handle from the front of the car I gently eased the ‘box backwards until it was free from the engine and lowered it to the ground. Due to the height of the car from the ground and as I may one day need to rebuild this box I placed some timber and polystyrene beneath the ‘box in case the worst happened and it fell from the jack. This came in handy as due to the imbalance of the ‘box on the jack it became easier to roll the ‘box from the jack and gradually remove timber until it was resting on the ground.

My patent-pending timber and polystyrene gearbox catcher


And just like that the first stage of the gearbox replacement was complete. The garage was locked up and I went indoors to enjoy a cup of tea and a shower whilst musing the prospect that I would not have the wonders of gravity to assist me when using my less-than-muscular arms to fit the new, even heavier overdrive gearbox…


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