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How to fit a fairey overdrive to your series land rover - pictures

by: Auto Express team

27 Sep 2017

Go to: How to fit a Fairey overdrive to your series Land Rover

When I bought my Series I 107 at auction last May, I knew that an overdrive would be high up on my list of improvements. It’s a 1955 example with a 2-litre petrol engine that has probably never had a major overhaul, and an overdr
Start by removing the seat cushions and unscrewing the centre panel from the top of the seat box to expose the transmission.
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You’ll now be able to access the transfer box on the back of the gearbox, which sends drive to front and rear axles.
To find the right position for the overdrive lever pivot, start by marking a point 108 mm above the end of the floorpan…
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…and then 54 mm towards the front bulkhead. This will provide a datum point from which to plot the exact spot for the pivot hole.
This aftermarket linkage kit is from James Cariss (eBay seller sjc798) for £65. It has an Oilite pivot bush – an improvement on the Fairey design.
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The pivot mounting bracket for the lever is bolted to the rear of the gearbox. It needed relieving with a grinder to clear the seat box flange.
With the bracket bolted on, make a small pilot hole through the tunnel side so that the drill bit marks the mounting bracket behind it.
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Measure the relative position of this mark to the centre of the pivot hole, and transfer these dimensions onto the side of the centre tunnel.
Now you have the correct position for the pivot hole on the tunnel side, which can be opened up with a 2 inch (50.8 mm) hole saw.
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To finish the pivot hole, a kit consisting of rubber seal, retaining ring and screws costs £9.50 plus p&p from Ian Hesketh (eBay seller ih02).
Clean up the edge of the pivot hole with emery paper and trial fit the pivot, just to check you got your measurements right earlier.
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Prior to bolting on the overdrive, you have to remove the end plate and top plate from the transfer box to access the mainshaft gear locking nut, which is castellated and deeply shouldered. It is secured with a locking tab washer
If you anticipate doing the job more than once, it may be worth buying the correct tool from HNJ Engineering for £79.95 plus p&p…
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…or alternatively, you could try making your own tool by grinding slots in a deep socket – but getting an accurate fit is not easy.
Once you’ve removed the nut, the large gear on the rear of the gearbox mainshaft will simply slide off the splined shaft.The overdrive clutch sleeve assembly fits in place of the gear that you’ve removed: drive passes into
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The overdrive clutch sleeve assembly fits in place of the gear that you’ve removed: drive passes into the overdrive via the splines inside the overdrive mainshaft and then exits again via the large output gear surrounding this ma
After sliding on the clutch sleeve unit, add a new lock tab washer and torque the nut to 100 lb ft. To prevent the vehicle moving as you tighten the nut, ask a friend to sit in the driver’s seat and press hard on the foot brake.&
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Push the rubber seal over the pivot, and then connect the pivot to the link while the link is still disconnected at the rear.
To reduce its shininess, you could spray the steel sealing ring with body colour; grey primer was an approximate match here.
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Remove the overdrive’s cover plate and fill with fresh EP90 oil to the level on the screw-in dipstick…
…and refill the transfer box until oil seeps out of this hole. Correct GL4-spec EP80W/90 oil is available from Classic Oils (www.classic-oils.net).
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Spot the (not so) deliberate mistake! The operating lever should be cranked out to the side and not forwards as shown here, or it will foul the gearlever in third and fourth.