gearing on 235/85x16

[drkwack]

Hi, sorry to drag this up, been out in mine at long last, seems to go quite well now, but feels over geared by a lot, acceleration isnt good even for a disco, cruises at 65 then takes alday to get any faster, reason Im thinking about the transfer box change is did the opposite on my 200 defender used a disco box and it went very well using same size tyres as disco is on now, any thoughts ??????????

[scube]

Hi

I have a similar problem with my Range Rover. You can either fit a defender transfer box which has a lower ratio or as I did hunt around for a transfer box from an MPI discovery which I have been told has the lowest ratio of all the Land Rover transfer boxes.

Changing the diffs to defender one's will also have a lesser effect to the over all gearing change but will also help which compensating for the tyre change.

Hope this helps.

Good luck, let us know how you get on.

[V8CAMEL]

Hi

I have a similar problem with my Range Rover. You can either fit a defender transfer box which has a lower ratio or as I did hunt around for a transfer box from an MPI discovery which I have been told has the lowest ratio of all the Land Rover transfer boxes.

Changing the diffs to defender one's will also have a lesser effect to the over all gearing change but will also help which compensating for the tyre change.

Hope this helps.

Good luck, let us know how you get on.

why will changing the diffs make a difference?

[Disco-Ron]

Changing the diffs will have NO effect, THEY'RE THE SAME RATIO!!!

I keep getting told i should fit a defender t box in mine, appaarently it will just make it easier to drive, no slower either....

[DaveSIIA]

Changing the diff's will have no effect whatsoever - Disco1 / RRC / Defender all use 3.54 diff's.

My 300Tdi 110 pulls happily on 235/85R16 driven through a RRC Borg warner transfer box (same ratio as Disco). Yours will feel higher geared compared to 205 or 235/70 tyres. Maybe a quick tweak of the injection pump will liberate a bit more grunt.

[drkwack]

mmm. mpi's are like rocking horse stuff, have tweaked the diaphram on the injector pump from 12 oclock to about 1/4 past (best way I could think of describing it) it does go a bit smoother and appears to cruise better, but am wondering what effect the power screw on the out side of injector pump will do. This screw has a locknut and fixed collar on it , has any one played with this side of things. ta. just had athought my disco speedo is electric where as the defender is mechanical, what about the mpi???

[scube]

I was only trying to help.

I was told sometime ago that the diffs were a different ratio.

Thank you very much for so kindly pointing out the error of my suggestion.

Noted. !

[Hybrid_From_Hell]

^^^

On LR4x4 if you don't KNOW for sure say, someone who doesn't actually know and

then "Helps" may cost someone serious money, so please bear in mind, if your not

100% sure.... FFS say so... then other will know its a maybe educated guess etc....

anyway

Diffs :

There are a selection,

3.54 LOTS of LR variants Most are RR Def Discos 90s etc,

3.9 Rover car

4.7 Series 1 2 3,

4.8 V Early series 1

4.1 Ashcrofts

This selection here are the most common..... not all are LR manufactuer

T Boxs there are a few too :

From Ashcrofts Website :

12D = 1.667 LT 230R

13D = 1.410 LT 230R

14D = 1.003 LT 230R

15D = 1.192 LT 230R

20D = 1.667 (2.5 N/A 110),

22D = 1.410 (all 4Cyl 90/110 bar above),

25D = 1.410 (V8 110 LT 85),

26D = 1.003 (RR Classic 3 speed auto),

27D = 1.192 (early RR Classic),

28D = 1.222 (RR and Disco I),

29D = 1.192 (V8 90 LT 85),

32D = 1.222

34D = 1.410 (2.0 Disco I),

36D = 1.211

38D = 1.211

40D = 1.211 (NAS/Japan 90&Disco),

41D = 1.211 (Disco II, diff lock stud),

42D = 1.211 (Disco II, diff lock stud),

43D = 1.410 (90/110 TD5),

57D = 1.410 (90/110 TD5),

61D = 1.211,

62D = 1.211,

68D = 1.211,

69D = 1.211,

70D = 1.211 (Disco II, no diff lock),

LT 230 Transfer case comparisons

1.003 > 1.222 = 17.92% Drop

1.003 > 1.410 = 28.86% Drop

1.003 > 1.667 = 39.83% Drop

1.222 > 1.003 = 21.80% Raise

1.222 > 1.410 = 13.33% Drop

1.222 > 1.667 = 26.70% Drop

1.410 > 1.003 = 40.57% Raise

1.410 > 1.222 = 15.38% Raise

1.410 > 1.667 = 15.41% Drop

1.667 > 1.003 = 66.20% Raise

1.667 > 1.222 = 36.41% Raise

1.667 > 1.410 = 18.22% Raise

For those considering a ratio change the following may prove useful.

MPH per 1000 rpm = 2.976D/ MTR

Run some calculations through the gear / speed calculator

FWIW I ran 235 x 85 x 16 and all was reasonable, all be it with a larey V8, but they are

not that much bigger than 7.50s which were and options on some 90s ??

Again FWIW having done the calcs I run a

1.192 TBox LT85 and ashcroft 4.1s and 34 simex

and have as close to factory 90 with 205 tyres gearing as near as damn it

Do some research some number crunching and see whats what

Nige

[mscowley]

I run 235x85x16 and with a decat pipe and a removed egr I also tweaked the pump on the screw at the back with the locking collar turned up half a turn and it now pulls away from my dads standard disco.

[BogMonster]

Easiest thing to do is set up a simple spreadsheet on Excel which you can alter the ratio figures and end up with a final drive ratio (i.e. gearbox x transfer box x diffs x tyre size) - plug in a set of figures for what you want (e.g. same as a 90 with std 1.41 t/box on 205R16 tyres), see what the overall drive ratio is, and then stick in what you want to change (e.g. bigger tyres) and see what else you can change to get back to about the same overall figure.

[drkwack]

WOW. thanks for the reply lads but you just got all to technical for me there, but will keep the info and try to get me head around it all. Didnt realise there were so many ratios to choose from again thanks

[Hybrid_From_Hell]

I have a program from a guy who was Ford R&D, and am happy to run some numbers

The 1st thing, and the base of it all is to have a start point - ie standard, ie how fast is a std version of what you have at say 3000 RPM in top,

then run what you have now and see the differences, then work out the best / cheapest / nearest mods to get you there

I need to know the following to run your "Standard"

What is your "Standard" truck

Engine (just so we know we are correct)

Gearbox and ratios for 1 2 3 4 5 gears

Transfer box Ratio

Tyres size Circumference (I may have this from my efforts so advise of the std tyres)

I then run the program and post up a PDF this will have high / low range, rpm 1 2 3 4 5th gears and 0-preset RPM

If it helps post away, the praogram is 100MB so no I can't do you a copy

Nige

[drkwack]

cheers mate , the car is a standard 300tdi egr(gone) uprated intercooler,turbo pipes and stainless single silencer exhaust all by twisted performance as far as i am aware the transfer box is a standard item (no sticker to donate ratio) tyres are 235/85x16 Insa turbo dakars, oh yeah its a disco the first post was using my old 90 as a comparison, much appreciated. No idea how fast yet so perhaps use land rovers advert blurb.