Defender Gearing

@dieseldog69 pointed out a few things to me about changing to a Disco tranny box on my 110. It's currently on 285/75/26 tyres which I shant be changing with a fender tx box and standard geared diffs.

Would I be over gearing the 110? According to DD I am currently 13% above standard and after the Disco tx I'd be 16.5% above standard. Is that too high?

I don't tow currently and no real plans for towing anytime soon. Most miles are motorway or country lanes, I do a fair bit of offroading and expedition type things (planning more of these) so I often have a fully loaded landy.

The idea behind wanting the Disco TX box was to improve motorway driving as I tend to do a lot of it and hopefully increase MPG.

Any suggestions and comments would be great!

with large tyres id have thought it would be too tall at times,4.1 cwps were popular for such

jamesmartin said:

with large tyres id have thought it would be too tall at times,4.1 cwps were popular for such

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What would changing to 4.1 cwps give me?

So would probably be better off with sticking to the fender ratio with a higher ratio 5th gear than a disco box?

bankz5152 said:

What would changing to 4.1 cwps give me?

So would probably be better off with sticking to the fender ratio with a higher ratio 5th gear than a disco box?

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knock of some of the higher gearing,bearing in mind your tyres and roof rack,
id would stick to 1.4 and over dive

I forget you start out with 235/85 16 as Disco starts out with 235/70 16 from factory but you do have the 1.4TXB where as the Disco has a 1.2TXB.

So from your initial start point of 235/85 16 and 1.4 TXB you have increased gearing by 5%+ with your tyres and would be at the same conundrum as me with (slight correction here, got my maths wrong earlier ) 13.5% gearing increase over standard with fitting a 1.2 Disco TXB.

On those tyres with a 1.2 I would be looking at 4.1 R&P set to bring the gearing back down. But as James says, an electronic OD would give you massive gains being 100% selectable as and when you need it without it affecting your gearing for off road and day to day driving.

As nice as OD would be, not really im the budget! I mainly ask about the tx box as i believe mine is on its way out.

From what you've both said it makes sense. I think Ill stick to fender gearing if for any reason i find I need a taller 5th its easily done. Was a wonderful thing on my 90

bankz5152 said:

@dieseldog69 pointed out a few things to me about changing to a Disco tranny box on my 110. It's currently on 285/75/26 tyres which I shant be changing with a fender tx box and standard geared diffs.

Would I be over gearing the 110? According to DD I am currently 13% above standard and after the Disco tx I'd be 16.5% above standard. Is that too high?

I don't tow currently and no real plans for towing anytime soon. Most miles are motorway or country lanes, I do a fair bit of offroading and expedition type things (planning more of these) so I often have a fully loaded landy.

The idea behind wanting the Disco TX box was to improve motorway driving as I tend to do a lot of it and hopefully increase MPG.

Any suggestions and comments would be great!

Click to expand...

Assuming you have 285r16s as 285r26 seems a bit extreme...
I have 285R16 ATs fitted ( did have 750R16s. ) and a disco box, on a 200TDI 110, I've also towed a boat with all up weight including trailer of 1 ton. I've not had a problem.
It is vastly better on motorways /dual carriageways . It's much quieter and more relaxed.
You can, when the engine is warmed up, trickle along at 30 on the flat in Fifth. You do have to drop down to 4th earlier for steep hills, but that's changing your gearing to near the standard 5th it's not a problem.
If you had to start a Landy, disco geared, towing a 1ton trailer up a 1 in 3. You'd just start in low box get up the hill then stop, change to normal box then continue. Not a problem..
With the above set up, I cruise at a true 65-70 not towing ( 60 on normal roads ) and get 32 mpg as average mph. I only tow at 50 on normal roads to be kinder to the boat...

1.22 on bigger tyres does not make a fast pull off. But improves top end.
I spend more time in 3-4 round here than chugging around in 5th.

Moons ago I looked at gearboxes I think it was jag or LDV/leyland daf that the top gear was different & you could still use a 1.44.