Please Note: This all relates to a 1972 SE5a with a 1974 Engine and Gearbox.
This is my version ( Don Kennedy ) of removing the Gearbox with Engine in the Car. I had removed and fitted the Engine, Gearbox and Overdrive as a complete unit a few months ago so I thought I would see how difficult it would be just removing the Gearbox/Overdrive with the Engine in the Car. My first comment is while it can be done by one person (I did it on my own) I would recommend that at least two people do the Job. The main reason is the weight of the Gearbox and Overdrive, it is VERY heavy. Reason for removing the Gearbox so soon after the rebuild?, the new Clutch Release Bearing started squeaking. I had read about doing this and part of the advice was to disconnect the Exhaust downpipes at the manifold, I managed to do this without disconnecting the Exhaust and without risking damage to any part of the Exhaust or manifold. Have small bags to put bits, nuts, bolts etc in and identify on the bag where they have come from. This is especially important if you are not expecting to complete the job that day, it is very easy to forget where the bits come from and a lot simpler when reassembling.
Remove Carburettor Air Cleaner.
Undo the Top two bolts that go from the top of bellhousing to Engine.
Reverse Car onto Ramps.
Jack up front of Car and put on Axel stands. If you want to get the Gearbox out from under the Car you will need at least 16 inches clearance under the Main Chassis for the bellhousing to clear.
Before getting under the Car make sure it is safe and secure and is is not going to fall etc.
A Scimitar landing on you is guaranteed to give you a sense of humour failure.
Remove Rear end of propshaft to axel bolts.
Remove Front end of propshaft from Overdrive, (Mine has a flange like the Axle End). I believe some have the propshaft that slides into the Overdrive. If so take care as when removed the Oil will escape. Drain Gearbox oil before removing propshaft if the Propshaft is the type that slides into the overdrive.
Disconnect leads to overdrive solenoid and inhibit switch at base of gearlever.
Disconnect leads to reverse light switch.
Remove plate between chassis sides under bellhousing.
Disconnect Speedo Cable.
Disconnect Gear linkages at base of Gear lever. Use some string to tie to the Overdrive as they "flop" about.
Disconnect Clutch Slave Cylinder, tie to one side. No need to disconnect the hydraulics.
Make sure the battery is disconnected before proceeding.
Remove two bolts holding Starter Motor. Slide Motor forward.
Use scissor jack to support engine under sump. Use a piece of wood between Jack and Sump to prevent damage. There is no need to lift the Engine, just support it.
Remove Half Round Plate at bottom of bellhousing.
Support Gearbox (Around the middle of the Gearbox) with Trolley Jack, this requires a Trolley Jack with wheels to enable you to move the Gearbox etc. If the ground is uneven it would be an idea to have a large sheet of wood to help it roll. It could be very difficult to move otherwise.
Remove bolts half way up bellhousing on both sides and bottom of bellhousing.
Remove Rear Gearbox mount plate; undo the centre bolt then the four bolts onto the chassis.
Now comes the time to separate the Bellhousing from the Engine. Using a screwdriver gently lever between the Engine and Bellhousing, when they have parted a small amount you will need to turn the whole unit anticlockwise (As viewed from the rear). The reason for this is the “Bump” in the bellhousing that the Starter Motor shaft went into, it will catch on the Chassis, turning it before the Bellhousing gets to far from the Engine will allow the whole unit to be lowered to the ground, failure to do so WILL result in the Bellhousing getting snagged on the left side of the chassis as the chassis narrows. Once the Bellhousing has turned enough (It will be obvious) the whole lot can be moved away from the Engine. Take care not to allow any weight to be taken by the first motion shaft (This is the shaft that comes out of the front of the Gearbox, goes through the Clutch Friction Plate and into the Flywheel) this can be difficult as the weight is being taken by the Trolley Jack and you need to turn it. If you are just replacing the Clutch the whole unit can be left on the Trolley Jack away from the Engine but take care as it could very easily slip off, I used a piece of wood 2”x 2” across and underneath where the Bellhousing and Gearbox joins. This piece of wood was held up and against the bottom of the chassis. There were times when this piece of wood was in the way but I felt happier knowing it was there.
As all the good books say reassembly is the reverse of the above. If you have never replaced a Clutch before make sure you have an alignment tool to align the Friction plate with the Flywheel Spigot Bearing. Trust me, trying to use the Gearbox first motion shaft or bits of round wood etc will result in hours of buggering about. I learnt this many years ago. If you are doing this alone (Mad Fool) it is difficult to get the First Motion Shaft to go through the Clutch Friction Plate and into the Flywheel Spigot Bearing. The “Secret” is to get the balance of the whole Gearbox etc correct on the Trolley Jack. Slightly back from the centre of the gearbox is about right. When the balance is correct it is quite easy to align so spend some time getting this balance correct. Take care, if the Gearbox etc comes off the Trolley Jack it will be a bugger to get back on by your self due to the weight. The only difficult part could be refitting the Bolt on the Top of the Starter Motor. I found this was best done from below, with the correct length extension on the socket going over the top of the Starter Motor. Do not tighten the bottom bolt first as this will cause problems fitting the top one. Make sure all bolts etc are fitted and tightened
(Another reason for putting the bits in bags, if all the bags are empty you must have fitted all the bits).
If you have never attempted this type of Job before I would recommend you give yourself at least one day but two days would be better in case you have a problem.
If you have done this type of job before and you hit no snags it could be done in less than 4 to 5 hours.
If I had to do this again I would remove the Engine and Gearbox as one unit.