Tell me I can't do this

I've just had an idea - it's so obvious it must be wrong!

I want to raise the gearing on the S2a to make it a bit easier on the road.
Overdrives and high-ratio t-boxes are expensive and I've just spent all my
pocket money on a new head and carb.

I also have a trialler (V8 auto with 90 axles) which may well be a better
trials vehicle with lower gearing - better control down hills etc .

Someone told me that the 4.7 diffs in the Series are a straight swap for the
3.54 diffs in the 90 axles. This would result in a 32% increase in gearing
for the S2a and a decrease of the same for Tiggrr.

Is it a straight swap, and would I need anything other than new gaskets?

I'm sure I must have missed something. Fingers crossed...

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)

Richard Brookman wrote:
> I've just had an idea - it's so obvious it must be wrong!
>
> I want to raise the gearing on the S2a to make it a bit easier on the road.
> Overdrives and high-ratio t-boxes are expensive and I've just spent all my
> pocket money on a new head and carb.
>
> I also have a trialler (V8 auto with 90 axles) which may well be a better
> trials vehicle with lower gearing - better control down hills etc .
>
> Someone told me that the 4.7 diffs in the Series are a straight swap for the
> 3.54 diffs in the 90 axles. This would result in a 32% increase in gearing
> for the S2a and a decrease of the same for Tiggrr.
>
> Is it a straight swap, and would I need anything other than new gaskets?
>
> I'm sure I must have missed something. Fingers crossed...
>

3.54 ratio Range Rover Classic diff heads are a straight swap - they've
got 10 spline axles (as you IIa should have if nothing's been changed).
And aside from new gaskets they are indeed all you will need. The
only downside is that they raise the drive ratio across the board - so
low range is not as low as it previously was. A happier medium is to
use Rover 90 diff heads (also a bolt in fit) that are 4.1 ratio. I've
run with both in my IIa and I feel that the 4.1s give a more usable
package overall (so they are what's in there at the moment).

--
EMB

"EMB" <[email protected]> wrote in message
news:[email protected]...
> Richard Brookman wrote:

> > Is it a straight swap, and would I need anything other than new gaskets?


If your 90 axles are late ones make sure at least one of the cast diff
housings has an oil filler/level plug hole on the side and put that one in
the rear axle or you may have trouble getting oil in it after fitting. It's
easier to weld a fitting in the rear diff pan whilst there is no diff fitted
for obvious reasons. Range Rover Classics are fine spline diffs with no side
oil fillers but early (two door types) usually have them and are 10 spline.


> 3.54 ratio Range Rover Classic diff heads are a straight swap - they've
> got 10 spline axles (as you IIa should have if nothing's been changed).
> And aside from new gaskets they are indeed all you will need. The
> only downside is that they raise the drive ratio across the board - so
> low range is not as low as it previously was. A happier medium is to
> use Rover 90 diff heads (also a bolt in fit) that are 4.1 ratio. I've
> run with both in my IIa and I feel that the 4.1s give a more usable
> package overall (so they are what's in there at the moment).
>
> --
> EMB

It doesn't seem like you are going to spend money playing with different
ratios but if you * do * then the older Rover cars were, I think, 4.3 :1 and
3.9 :1, but not 4.1 as ISTR. I don't think you would find a pair of these
anyway today.

HTH Martin

so Oily was, like...
> "EMB" <[email protected]> wrote in message
> news:[email protected]...
>> Richard Brookman wrote:
>
>>> Is it a straight swap, and would I need anything other than new
>>> gaskets?
>
>
> If your 90 axles are late ones make sure at least one of the cast diff
> housings has an oil filler/level plug hole on the side and put that
> one in the rear axle or you may have trouble getting oil in it after
> fitting. It's easier to weld a fitting in the rear diff pan whilst
> there is no diff fitted for obvious reasons. Range Rover Classics are
> fine spline diffs with no side oil fillers but early (two door types)
> usually have them and are 10 spline.
>
>
>> 3.54 ratio Range Rover Classic diff heads are a straight swap -
>> they've got 10 spline axles (as you IIa should have if nothing's
>> been changed). And aside from new gaskets they are indeed all you
>> will need. The only downside is that they raise the drive ratio
>> across the board - so low range is not as low as it previously was.
>> A happier medium is to use Rover 90 diff heads (also a bolt in fit)
>> that are 4.1 ratio. I've run with both in my IIa and I feel that
>> the 4.1s give a more usable package overall (so they are what's in
>> there at the moment).
>>
>> --
>> EMB
>
> It doesn't seem like you are going to spend money playing with
> different ratios but if you * do * then the older Rover cars were, I
> think, 4.3 :1 and
> 3.9 :1, but not 4.1 as ISTR. I don't think you would find a pair of
> these anyway today.
>
> HTH Martin

Thanks EMB and Martin. As long as the 90 axles contain 10-spline diffs
(easy to check) I can do the swap and see how it goes. In fact, all I have
to do is swap the rears and remember to stay in 2WD. If the 90 diffs prove
too much for 2.25 litres of naked power, I can always swap back and look for
something in the middle.

Thanks for the help.

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)

On or around Mon, 8 Aug 2005 20:51:04 +0100, "Richard Brookman"
<[email protected]> enlightened us thusly:

>
>Thanks EMB and Martin. As long as the 90 axles contain 10-spline diffs
>(easy to check) I can do the swap and see how it goes. In fact, all I have
>to do is swap the rears and remember to stay in 2WD. If the 90 diffs prove
>too much for 2.25 litres of naked power, I can always swap back and look for
>something in the middle.

the new old toy (now christened Edward II) doesn't feel as though he needs
any higher ratios. Mind, the LWB is a lot heavier than an SWB - the SWB
series II would pull to an indicated 77, and revved rather a lot in the
process.
--
Austin Shackles. www.ddol-las.net my opinions are just that
Confidence: Before important work meetings, boost your confidence by
reading a few pages from "The Tibetan Book of the Dead"
from the Little Book of Complete B***ocks by Alistair Beaton.

so Austin Shackles was, like...
> the new old toy (now christened Edward II) doesn't feel as though he
> needs any higher ratios. Mind, the LWB is a lot heavier than an SWB
> - the SWB series II would pull to an indicated 77, and revved rather
> a lot in the process.

The S2a hasn't been above 65 in my ownership, and that was downhill with a
following wind. 50-55 is a good cruise, and it feels as if it will pull a
lot more, but the revs are high. I'm hoping higher gearing will let me
drive at the same speeds with less need for ear defenders.

--
Rich
==============================
Disco 300 Tdi auto
S2a 88" SW
Tiggrr (V8 trialler)