Diff Ratios

[white90]

Mike Mac

(Member)

11/26/01 09:11 PM

66.8.25.61

Diff Ratios Reply

I have a Range Rover Classic with 35inch tyres fitted which has affected the gear ratios. Does anyone have any experience with the lowering of diff ratios, changing the gear ratios, transfer box ratios etc. I am looking for the best option to reduce my gear ratios. Any advise will be appreciated.

The vehcile is used for serious off road work so strength is of utmost importance.

Post Extras:

keng

(Member)

11/26/01 11:56 PM

195.228.231.60

Re: Diff Ratios Reply

Try ascroft auto transmissions: www.autoconv.com

Post Extras:

Ian Ashcroft

(Member)

11/29/01 04:40 PM

195.7.235.97

Re: Diff Ratios Reply

Hi,

we sell 4.11 R & P gears exactly for this problem,

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Mike Mac

(Member)

12/03/01 04:19 PM

66.8.87.11

Re: Diff Ratios Reply

Hi Dave

I sent you an e-mail recently quering what are the best options avaiable. Did you receive it?

I have been to your site and was wondering if the 4.11 or 4.7 would be the best option.

I intend using my Rangie for competition and have had problems with the 3rd diff. I have been advised to change to a R 380 gear box. Is this a good option in terms of strength? What are the gear ratios?

Your advise will be appreciated.

Post Extras:

Mike Mac

(Member)

12/07/01 06:51 PM

66.8.87.11

Re: Diff Ratios Reply

I am trying to contact someone from Asccroft Transmissions. Does anyone perhaps have their correct e-mail address?

Post Extras:

Diff

(Member)

12/07/01 07:06 PM

217.205.214.196

Re: Diff Ratios Reply

dave@ashcrofttrans.ndo.co.uk

Post Extras:

Ian Ashcroft

(Member)

12/10/01 01:48 AM

195.7.235.46

Re: Diff Ratios Reply

Hi,

sorry for the delay,

If you want to lower both hi and lo range then the 4.11 gears will do this nicely, if you are just worried about hi then you can either fit a lower ratio LT 230, ie 1.667 or 1.410 (your hi range is now 1.222) or if you have a post 1989 RR you have the Borg Warner transfer case and to drop the hi ratio in this you can fit a chain & sprocket kit which will drop hi from 1.206 to 1.37 ratio, (low will also be droped),

3 problems with the 4.75 R & P gears,

1) Too low

2) the lower the R & P ratio the weaker they get because the lower the ratio the small diameter the pinion gear, thus the fewer the teeth, thus you get the same load going through less teeth, this is one of the reasons why a 3.54 is strong compared to the series 4.7 diff.

3) We don't make them anymore !

you mention you are having problems with the 3rd diff and have been advised to change to the R 380 and wonder what the ratio implications are,

a few points here,

the centre diff is in the transfer case thus changing the mainbox will have no effect on it.

I sometimes get asked for stronger centre diff cross pins to which my answer is, yes but if you use the centre diff properly you don't need one ! the only reason the centre diff breaks is because you are off road, wheel spinning with out it locked, lock it as soon as you get off the tarmac and it will not break again.

the ratios in the 5 speed boxes do vary a little but not much at all, stick to changing the transfer case or R & P gears,

hope this helps,

Post Extras:

Mike Mac

(Member)

12/10/01 09:19 PM

66.8.87.11

Re: Diff Ratios Reply

Hi Dave

Thanks for the advise. Just one or two points I need clarity on.

The RR is a 1983 and to the best of my knowledge (not always correct)the main and transfer box on this vehicle come as one piece.

The reason for my query is that I use the vehcile for competition and need a "crawler Gear". ie a lower low range. The high range is not of major concern, however could benefit from being slightly lower due to larger tyres.

I have been told that the R 380 main box with transfer box (I am not sure of the model) is stronger. Not that the R380 is stronger than the current one I have but that the transfer box and 3rd diff that are attached to the R380 is stronger. Are you saying that this is not the case? We do sometimes unlock the centre diff to pull wheels around etc.

What are the gear ratios of the R380 and the respective transfer box?

Once again your advise will be appreciated.

Post Extras:

Ian Ashcroft

(Member)

12/11/01 03:54 PM

195.7.235.5

Re: Diff Ratios Reply

Hi,

you have the LT 95, 4 speed manual box, I do not know of a way to lower low range and thus if you are sticking with this mainbox I can only advise going for the 4.11 R & P route.

The R 380's vary in strength depending on the suffix used but none I would say the R 380 / LT 230 combo is not notably stronger than the LT 95 set up.

both the LT 95 and the LT 230 have a low range step down of 3.321, 1st gear in both the R 380 boxes and the LT 95 varied and thus I cannot quite figures but the difference is very little.