2.25d with disco diffs

Gents (and any ladies (doubt it though))

Im considering fitting some disco diffs to my S3 LW. She has a 2.25 diesel and runs ok but what Id like to know is would the engine be man enough to power the change in gearing??

Many thanks

What size tyres are you running the standard 750's?
The reason I ask is I have an SWB with an overdrive that originally had 205 tyres fitted. When I changed to 7.50's not only did the acceleration slow significantly (and it was not quick to begin with!!) but I had to be going faster before I could engage the overdrive as the engine would not pull the higher gearing. I also now have have to drop out of the overdrive as soon as there is any hint of an uphill slope otherwise it will grind to a halt. None of this is a problem and I am much happier with the larger tyres but it was a significant change and required a change in driving style.
Swapping the diffs would give you roughly a 30% increase in gearing over standard by my calculations, whereas I believe my overdrive (fairy) gives a 20% increase in gear ratio. The difference being yours will be across all gears rather than selectable.
Although I cannot say for sure, I would expect the engine would pull it reluctantly and acceleration would be slow, however you may find you spend a lot more time in 3rd gear where previously you would have been able to use 4th. Similar to my experience of increasing the gearing through tyre size where I now spend more time in 4th rather than overdrive.

I wouldn't, not with a doozal 2 1/4.

Save up for a good O/D, it'll give you an extra gear between 3rd/4th and a 5th which is far more useful on an already underpowered injun.

dag019 said:

What size tyres are you running the standard 750's?
The reason I ask is I have an SWB with an overdrive that originally had 205 tyres fitted. When I changed to 7.50's not only did the acceleration slow significantly (and it was not quick to begin with!!) but I had to be going faster before I could engage the overdrive as the engine would not pull the higher gearing. I also now have have to drop out of the overdrive as soon as there is any hint of an uphill slope otherwise it will grind to a halt. None of this is a problem and I am much happier with the larger tyres but it was a significant change and required a change in driving style.
Swapping the diffs would give you roughly a 30% increase in gearing over standard by my calculations, whereas I believe my overdrive (fairy) gives a 20% increase in gear ratio. The difference being yours will be across all gears rather than selectable.
Although I cannot say for sure, I would expect the engine would pull it reluctantly and acceleration would be slow, however you may find you spend a lot more time in 3rd gear where previously you would have been able to use 4th. Similar to my experience of increasing the gearing through tyre size where I now spend more time in 4th rather than overdrive.

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Minor detail but iirc O/D is 27%

blue beasty said:

Minor detail but iirc O/D is 27%

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Quite happy to be corrected. The diff ratio may not be totally accurate either as they were from a distant memory when I was looking into it.

Have now looked up the diff ratios, according to a quick google they are:

• Stock Series differential ratio - 4.7:1
• Stock coiler differential ratio - 3.54:1

Using these numbers I think the diff change will give you a 33% increase in gearing across all gears.

I need to fit some new tyres on it anyway due to cracks on the current ones. I have a OD already. As for hills I live in norfolk!! I think I might eventually drop in a 200 tdi or a rover v8 as I want to use the LW as a daily. Mind you I have used it as a daily before and enjoyed it as it is.

My SWB runs quite well with the higher ratio diffs. It has the 2.5 nas diesel. I think the 7.50 tyres with the the overdrive is probably the better option. But why not stick a diff in the back and give it a try. Also it is a pain filling the diff through the breather hole or in the end of the axle.

Billy

I suppose and that way all i need to do is get some tyres which I need to anyhow. Any recommendations for tyres? I mainly drive on road and have the old style wheels.

I would think it will be over geared...lnock your speedo out by around 25-30%

I fitted them to mine with its 200di engine...and its fine.

Good suggestion...try one in the rear and see how it goes.

nickjaxe said:

I would think it will be over geared...lnock your speedo out by around 25-30%

I fitted them to mine with its 200di engine...and its fine.

Good suggestion...try one in the rear and see how it goes.

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I guess I could try one on the back first

Use the Ashcroft ration calulator - you can try some changes and see what diference they make. My S2A has 3,54 diffs to which I added 235/85 tyres and an OD to get around 2000 rpm at 60 as I have th e3.3L Perkins that pushes most of its torque out below 2000 rpm. Going from 205 to 235 made a huge difference, about 5 mph at 50 for the same revs.

gipsybilly said:

Also it is a pain filling the diff through the breather hole or in the end of the axle.

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Just replace the diff pan with one with a filling plug and the problem is solved.

MadManish said:

I suppose and that way all i need to do is get some tyres which I need to anyhow. Any recommendations for tyres? I mainly drive on road and have the old style wheels.

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I prefer 7.50’s to modern metric sizes. But there is less choice. If you want originality I like the deestone extra traction but they are noisy on the road. I run Michelin ZXL’s on mine and have no complaints. They are quieter than the extra traction’s. And handle the road well at series speeds.

dag019 said:

I prefer 7.50’s to modern metric sizes. But there is less choice. If you want originality I like the deestone extra traction but they are noisy on the road. I run Michelin ZXL’s on mine and have no complaints. They are quieter than the extra traction’s. And handle the road well at series speeds.

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Hows about avon rangemasters?? Them michelins are rather pricey!! Just wondered how bad are the deesontes anyhow??

The BFG All terrains in a 235/85 look very simalar to a 7.50 when fitted to a std LR rim as its the narrowest allowed fitting. Worth trawling e-bay for a used set as they last a long time.

MadManish said:

Hows about avon rangemasters?? Them michelins are rather pricey!! Just wondered how bad are the deesontes anyhow??

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Rangemasters are a very good tyre, and the deestones are probably fine on a series.

MadManish said:

Hows about avon rangemasters?? Them michelins are rather pricey!! Just wondered how bad are the deesontes anyhow??

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The deestones are fine at series speeds but I would not want to fit them to anything quicker. They do rumble along the road. Not as bad as the old super all grips though. They used to howl.
Although 235/85 are the nearest metric equivalent I think they look very differant when fitted and prefer a proper 7.50. The Michelin’s are very expensive new but co e up second had fairly often. And regularly cone up in the MOD disposal auctions.

dag019 said:

The deestones are fine at series speeds but I would not want to fit them to anything quicker. They do rumble along the road. Not as bad as the old super all grips though. They used to howl.
Although 235/85 are the nearest metric equivalent I think they look very differant when fitted and prefer a proper 7.50. The Michelin’s are very expensive new but co e up second had fairly often. And regularly cone up in the MOD disposal auctions.

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There was a chap on the forum selling a set of slightly worn Michelins on Series wheels for £50 a while ago. Not sure if he sold them yet or not.
They looked like a good buy to me.