CIW2032 · Jan 19, 2008

I am quite new to the wonderful world of LR's. I have a '74 Series III all original and been in the family most of its life.

I have been considering buying a Fairey O/D in order to improve road performance (engine speed reduction and fuel economy rather than top end speed) but have read a couple of articles on changing the cogs in the gearbox to alter ratios as having a similar effect.

I am prepared to sacrifice some off road ability in favour of tarmac comfort.

Any advice on the pro's and cons of the gearbox approach appreciated.

mistericeman · Jan 19, 2008

well for what its worth ,ive got a series 3 88" running standard defender axles and 7.50 tyres,with a 2.5 transit diesel,and found it screamed at anything over about 45 mph (indicated) ,but after fitting an overdrive its like a differant car ,tops out about 55/60 mph ,and sounds a whole load better ,and its switchable too ,so doesnt affect lowrange off road ,best money i spent imho

yella · Jan 19, 2008

have you considered changing the diffs for rangerover uns, that will up yer top end

G-man · Jan 20, 2008

yella said:
have you considered changing the diffs for rangerover uns, that will up yer top end

if its a 109" it might have a sailsbury rear axle (like mine) but i would fit the O/D, i am gonna re-fit mine when i get a chance to re-build it

CIW2032 · Jan 20, 2008

Thanks - it is an 88". I wanted to retain as much originality as possible so would prefer not to fit RR diffs etc.

Just wondered if anybody has gone for the larger cog route - Fairey's on FleaBay are not cheap and it can be a gamble what you get in terms of quality whereas a set of new cogs would (should) give years more service.

Grippa · Jan 20, 2008

A gearbox rebuild int cheap either. I have heard of the conversion, but you'd have to be bluddy skilled ter do it I reckon. By the time you'd paid someone like Ashcroft to rebuild yer box an O/D would look a pretty reasonable way to go.

Fitting them is a piece o' **** & I've seen quite a few being sold while still fitted to the original vehicle so's you can check them working.

yella · Jan 20, 2008

so you want to keep its originality but you want to change the innards of the gearbox.isnt that like swapiing the diffs? ie. keeping the original axle casings but swapping the innards???

Grippa · Jan 20, 2008

Aye, know what yer mean, s'not as if yer can see 'em.

Wun't a standard 88" be a bit sluggish wiv RR diffs tho'? Wiv a V8 they're about right, wun't have fancied me ol' 2.25 doosul wiv RR diffs. It's 0-60 time would have got me frum my gaff ter yours I reckon!

yella · Jan 20, 2008

aye but he were after top end rather than acceleration

TP1 · Jan 20, 2008

Grippa said:
Wun't a standard 88" be a bit sluggish wiv RR diffs tho'? Wiv a V8 they're about right, wun't have fancied me ol' 2.25 doosul wiv RR diffs. It's 0-60 time would have got me frum my gaff ter yours I reckon!

....
I fort series 0-60 times were measured in lunar months

Grippa · Jan 20, 2008

Not wiv a V8!

CharlesY · Jan 20, 2008

It doesn't matter HOW his Landy is geared up, the effect will be same - SLUG-A-BUG slower off the mark and up to "speed".

Using the OD, he retains everything he had by way of "performance" but ADDS on top of that the long legs when he wants it.

Doesn't seem like a contest to me, £250 and a couple of hours for the OD job complete versus at least twice that and a fortnight's labour to rebuild the gearbox with all new gears and bearings.

CharlesY

mistericeman · Jan 20, 2008

as above ,overdrive = switchable

just make sure you buy one that you can hear working ,or off someone trustworthy ......if you want a contact pm me ,for the name of some one you can trust

CIW2032 · Jan 21, 2008

Thanks all - Overdrive it is

CharlesY · Jan 21, 2008

CIW2032 said:
Thanks all - Overdrive it is

Way to go!

And remember this, YOU control the OD, and you can engage it and leave it that way if YOU like, which would be the same as having RR diffs.

But most people use the OD AFTER they hit top gear, simply as an overdrive, because the ratios in a 4 speed landy box are quite good as they are.

The thing is, this way YOU get the choose from 20 forward gears and 4 reverse!

CharlesY

TP1 · Jan 21, 2008

CharlesY said:
Way to go!

And remember this, YOU control the OD, and you can engage it and leave it that way if YOU like, which would be the same as having RR diffs.

But most people use the OD AFTER they hit top gear, simply as an overdrive, because the ratios in a 4 speed landy box are quite good as they are.

The thing is, this way YOU get the choose from 20 forward gears and 4 reverse!

CharlesY

....
That'll be 16 forward and 4 reverse unless you fit a 5 speed box

CharlesY · Jan 21, 2008

TP1 said:
....
That'll be 16 forward and 4 reverse unless you fit a 5 speed box

You're not counting 4 economy gears with the gear stick in the central waggling position and the OD and / or transfer too, and her and the kids pushing from the back. It's called crawler gears.

Sixteen it is!

CharlesY

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