This was a Conversion from Automatic to Manual on my 1972 GTE SE5a. Completed August 2004. I considered it easier to purchase a Donor Car ( 1974 GTE ) that was beyond saving due to Very Poor Chassis. This proved to be a Very good idea due to the Odds and Sods required. i.e. Nuts, Bolts fittings etc. Parts that I could take off the Donor Car. It also helped as taking the parts off the Donor Car showed me how the Bits and Parts were fitted. The cost of a Donor Car (MOT Failure) proved to be cheaper that the advertised costs of a Manual / Overdrive Gearbox and other Parts.
There is full information in Text at the bottom of this page.
Click on Picture's for Larger View.
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What an Engine and Gearbox looks like after 30+ Years under a Scimitar GTE.
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After Spending a Few Pennies, a Clean and a Rebuild. That looks better.
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Out it comes. Ain't it Heavy !. Lands in Front of Donor Car. Hole Ready for New Engine.
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Engine in, Ancillaries Fitted. It Works !. and no Leaks.
Ignore lovely Wiring. See "Rewire"
For Spark Plug Firing Order click below.
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Even looks Nice Underneath. Am I Sad or Meticulous ?.
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Converting from Automatic to Manual.
I hope the following does not put you off. I used the Engine and Gearbox complete from a Donor Car (After rebuilding the Engine). There are lots of Scimitars that are MOT failures going cheap and you will probably find they are cheaper than buying just the Gearbox, this is a lot easier as all the bits required are there. It is surprising how many bits are required, i.e. odd nuts bolts etc. It will also enable you if possible to drive the Car and Test the Gearbox and Overdrive. If just a Manual Gearbox and Overdrive is obtained you will also need the Bell Housing, Flywheel and Clutch (all three bits) a Three Pedal Box for the Clutch Pedal and a Manual Propshaft. Also required will be a Clutch Master and Slave Cylinder and the Hydraulic Pipe between the two cylinders, if the cylinders have not come from a Donor Car ensure that you have the part that screws onto the Master Cylinder Push Rod, it’s the bit that connects the push rod to the pedal. You will also need the Third/Fourth Gear switch for Overdrive, this is required to ensure that Overdrive can only be selected in third and fourth gears, if this switch is not used Overdrive can be selected at any time and in any gear, could be dangerous as if reverse is used when Overdrive is engaged say Good buy to the Overdrive. Another reason a Donor Car is better is the Gear Lever assembly bolts direct onto the Transmission Tunnel (more later) and the holes etc are not only different but there is a slight angle to the right in the Top of the Transmission Tunnel, this allows the Gear Lever to be upright, If the Lever assembly is bolted direct to an automatic transmission tunnel the Gear Lever will be angled towards the passenger seat and the Linkage below will foul the side of the Transmission Tunnel. There may be a difference with the Bearing in the Flywheel where the Gearbox shaft goes into the Flywheel, another reason for a Donor Car. If you are fitting the Gearbox and Overdrive to the Engine while the Engine is in the Car good luck, it is a heavy lump to heave about under the Car, see here for how to remove Gearbox with Engine in the Car. There was no wiring on my car for Overdrive but it is easy. Remove the Switch and Indicator (Blue Light Thingy) from the Dashboard of the Donor Car, or get a Switch and Indicator Lamp. The Solenoid on the Overdrive has its own earth. The other connection from the Solenoid goes through the Third/Fourth gear switch on the bottom of the Gear Linkage (If you can, take note of how it was bolted on before you remove it) then from this switch to one side of the Overdrive Switch on the Dashboard, the other side of the Switch on the dashboard connects to a Live Ignition Feed on the Fusebox. The Blue Indicator Light is connected to the “Overdrive” side of the Switch and the other connection to earth (The Rev. Counter Earth can be used). I connected mine different, I connected the Overdrive Indicator Light at the Switched Live Feed Connection direct on the Solenoid, reason, If there is a problem I will know if the Live 12Volt Feed is getting to the Solenoid. This means two wires from Overdrive to switch and light but not a problem. Note that the Overdrive On Warning Light was not an original fitment, there was no light fitted by Reliant. The Pedal Box is interesting, you need to make a hole for the Clutch Master Cylinder and bolts. Not as difficult as first seems but the middle hole has to be large to get the center of the Cylinder through. When removing the Old Pedal Box remember to take off the Brake Master Cylinder Bolts. The Pedal Box is held on by three bolts, two can be seen at the top looking underneath the Master Cylinders and the third is slightly forward and lower. Remove split pin in the Brake Pedal to Shaft Pin then remove pin and the Pedal Box comes out. Takes a bit of a “Wiggle” but if when pulling it you pull down slightly as well it seems to come out easier. If you remove the Drivers Seat before starting you will find it a LOT easier. Make the holes for the Clutch Master Cylinder then fit the three pedal box. I am fortunate that I have small feet. If I had to remove the Pedal Box for any reason I would Bend the Clutch Pedal to the left a bit (about 1 inch). I think it would be difficult to bend without the correct equipment but worth thinking about depending upon the size of your feet. If you can get help fitting the Pedal Box it will be easier as it is difficult to see if you are aligning it correctly. The Clutch Pedal will be held down and in place by the Shaft from the Master Cylinder. Just before fitting the Pedal Box connect the Accelerator Cable to the pedal linkage and thread through the hole when fitting the pedal box, that will make things a lot easier later (Don’t ask me how I know, I just know !). Pictures of the Pedal Box can be seen below. The real interesting bit was the Gear Linkage. I was advised as below but I tried a different way, It looked easy just to make the hole in the transmission tunnel bigger. Don’t waste your time trying anything different than this. Cut out the area around the Gearlinkage on the Donor Car. Make the cut at the point where the tunnel curves from the top to the sides and a few inches in front and behind the Gearlinkage. If you look carefully you will see where the curves etc match between both Cars. No need to be exact. You will now have to cut a big hole it the Tunnel of the Car, about 1 ½ to 2 inches smaller that the Bit you have cut out but before you cut the hole you have to have the Gearlever fitted to the piece you have cut from the Donor car to ensure the hole is in the correct place. All will become clear by now. The reason for cutting out part of the Donor Car Tunnel is due to the Gearlinkage having to be mounted not level with the Tunnel Top but at a slight angle to the right. When you have fitted the linkage onto the Gearlever and are sure all is OK get some fibreglass and resin and glass around the area to attach the Cut out piece of tunnel to the Existing Tunnel. I hope I have made this bit make sense, this was the way it was advised to me to do it. I thought it was a lot of messing about and tried other ways but wasted a lot of time. If you look at both Gearlever areas on both Cars it will make sense. If you do not have a Donor Car you will need to make sure that the gear Linkage is in the correct position, i.e. pointing straight up when in neutral. The rest is normal connection stuff with the Linkage below. Now fit the Clutch Slave Cylinder. Make sure that the Clutch Slave Cylinder has the bleed nipple at the Top; it will make for easier bleeding. I have read a lot about the problems of bleeding the Clutch, Try gravity! Fill the Master Cylinder; undo the bleed nipple pump pedal a couple of times then allow the fluid to drip out of the nipple. Keep your eye on the fluid level as it will take about 10 minutes for the Master Cylinder to empty, keep topping up and after about one Master Cylinder of fluid tighten the nipple and the pedal should be hard and ready to go. There are other bits that are obvious as you go. If you remove and fit the Engine and Gearbox in one lump the easy (?) way to lift it is to get the “Balance” point about level with the center of the Carb mounting (Or slightly rearward, 1 to 2 inches ). When all disconnected from the Engine including the Engine mounts you should only have two bolts on each side of the rear gearbox mounting into the Chassis and the Engine Mounts just resting in position. The radiator and chassis cross member should be removed. Take the weight with the hoist then undo the two rear bolts on the Gearbox to Chassis Plate, take care in case the balance is not correct as the rear of the box may suddenly drop. The whole lump should be ready to remove. Lift it until the Engine mounts come away from the chassis brackets. Then lift a bit then push the Car back a bit, then lift a bit then push the Car back a bit. The only bit that is a tight is the Exhaust manifold which will try to snag on the steering column but it is easy to manoeuvre past it. Obviously you need to make sure you have enough room behind the Car to allow it to go backward enough. This is the best way to remove the Lump as the Engine/Box is VERY heavy and to manoeuvre with the hoist is difficult. Make sure the Hoist is up to the Job and if using rope take care where the rope goes under the Engine as the edge of the sump can cut the rope ( Once again, don’t ask me how I know, I just know !!! ). Refitting is the reverse of removal but the "Secret" is to keep the whole assembly as level as possible, i.e. allow the rear of the Gearbox/Overdrive to clear the bulkhead then keep it up and into the Transmission Tunnel. Failure to do this will make the Rocker Covers foul the Bulkhead before the Engine Mounts are aligned.
What the Pedal 
Box looks like.
I hope I have explained OK as it is difficult to explain some things, better if I could show you.
The above was done by myself, no other help. It would be easier and quicker if there is Two of you.