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overdrive


richo
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I'd like to buy myself an overdrive for my landrover series 3 but haven't got a clue about fitting it. Is it an easy job, is there anything I've got to be careful about? would a second hand one be alright or should I buy a new one (if it's possible to get a new one at all)? thanks

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They're easy to fit. The most difficult part is fitting the linkage to engage and disengage the overdrive, which bolts onto the top of the gearbox. You may need to cut a hole in the transmission tunnel cover for the lever to go through.

I'm not sure about suppliers for new overdrives (I think Roverdrive is one?), but what I can tell you about second hand ones is they can be hit and miss. Some can have little wear and be in excellent condition, others can have a lot of wear and scream away before eventually going clonk giving you no drive. Or they can go clonk and still give you no drive if the input splines are badly worn and strip.

Two main types that are floating around in the second hand market is the Toro Overdrive (stronger, bigger oil capacity) and the much more common Fairey Overdrive. You can get parts for the Fairey to repair, but Toro parts are hard to source.

As for the fitting of the overdrive to the transfer box, it's a relatively simple procedure. You don't even need to drain the transfer box to do this job. Unbolt the rear access cover, it has six nuts if I remember rightly, and remove it. You will also need to gain access to the top of the transfer box ideally, and remove the top cover to see the output shaft. Unless you have the special tool a screwdriver works to undo the retaining nut that you will see.

You will have a large gear visible on the gearbox output shaft, with an unusual retaining nut with a locking tab. Undo the tab and get a screwdriver and gently begin tapping the nut's edges. It'll start to unwind, be careful not to start chiselling away at it! Once it has unwound, remove it along with its locking tab. Following this, the output gear should slide off the output shaft.

Next you need to get the replacement output drive section that will act as part of the input to the Overdrive. This goes on the same way that the drive gear came off. It'll have a section of roller bearings to support the input shaft of the overdrive, I'm not sure if that is separate for a Fairey but on my Toro it's integrated with the splines. Refit the unusual nut with its locking tab, and then lock the tab on the nut again.

Here comes the fiddly bit. Fitting the physical overdrive in place. You need to lift it up from under the vehicle and slide it in. You have to get the splines lined up and the output gear on the overdrive lined up with the transfer box gears for it to slide in. After that, it's a matter of just bolting it up accordingly and fill it with oil.

Not the best guide around by a long way, but it should give you a better idea of what is involved I hope.

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The overdrive manufacturers supply special locking tabs for the castellated nut on the back of the mainshaft. The difference is that they are slightly smaller diameter - and if a standard one is used the unused locking tabs will stick up too far to allow the overdirve to be fitted. So have a look before fitting and trim ALL the tabs before fitting the nut (Which must be done up 85 Lb Ft)

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  • 3 months later...

I am in the running for a new ®overdrive and because of the waiting (over one year now) thinking of leaving the overdrive out -what if there is a problem with the drive and you'll have to wait years for spares-; but does anyone has experience with this roverdrive, are they build to last or trouble makers?

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I am in the running for a new ®overdrive and because of the waiting (over one year now) thinking of leaving the overdrive out -what if there is a problem with the drive and you'll have to wait years for spares-; but does anyone has experience with this roverdrive, are they build to last or trouble makers?
I have been using one for a bit over three years, with a Tdi pulling the heavy 109 on autoroutes and up 1:3 skislopes and up to 10,500' glaciers in the Alps while fully laden and it's running beautifully. I don't think the Fairey I had before it would have survived the Tdi transplant and certainly not that trip.

For Fairey overdrive fitting, this may help: http://www.nickslandrover.co.uk/archives/619

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Roverdrives have been unobtainable for a year but are back in production and those on the UK waiting list should get theirs by the end of this month or early July. The new units have nicer looking castings than before and an improved shorter shift pattern. The linkage has also been upgraded with nylon lined rod ends. See www.roverdrives.com

Ray Wood in Vancouver

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