Info on diff gearing

[Lewy]

G'day guys.

I am looking at getting my diff gears done. I have emailed the place that has done a far bit of work for me. I'll post up what they said and was wondering what people's thoughts are! My patrol is a 4.2tdi wagon 2003 with 285s and all the goodies, rear bar, bull and winch and so on so she's got a bit of weight to hall around! I have also done the 5th gear up grade and it now sits at 1850-1900 rpm at 100kmh witch is a little low! Anyhoo this is what the gear box place had to say.

I think at minim you would have to use 4.3 ratio, your gu should be 3.91 now, going to 4.3 with set up you have & basing the rpm at 1900 you should jump to 2100 rpm.

Your next option would be 4.6 ratio which will run around 2250 rpm.

4.3 ratio will make a difference for you, but 4.6 will be the biggest gain, as this will really help your take off, but will all so make your low range even lower for easy crawling.

So any info and or your ideas would be great.

Cheers
Lewy

[nissannewby]

If you carry a bit of weight than 4.3'a will be spot on, however I would be checking your build plate to see what your current ratio is, I am fairly certain most 4.2's were 4.11. 4.6's will be to much unless you want to run bigger Tyres again.

You could also go back to 265's as an option.

[MudRunnerTD]

My GUIV runs 3.9s too. If I was going to do it it would be 4.3s

[Lewy]

Ok great. Thanks for that!! Where dose it say on my build plate? I'll go have a look.
I'd say I will always run the 285s I find them to be a great size tyre.

Lewy!

[MudRunnerTD]

Bottom right corner of the compliance plate will be a number and letters, part of which will be either 3.9 or 4.11

[Lewy]

Yep just checked and it says hg39 so it's a 3.9 diff. So looks like going to to 4.3 will be best for me. And 2100rpm at 100kph seems to be right on the money. A little lower than standed but not so low that I have no power!

Cheers
Lewy.

[BigRAWesty]

This is weird. 5th gear mod? Head of them for strengthening them, but thought they were the same ratios.

Given you have bigger tyres, metric is over my head so simply
31' tyres = Stock ratio, 3.9 in your case
33' tyres = 4.11 ratios will correct the Speedo,
And for a 35' Tyre the 4.3's will bring it somewhat close..
Have you had transfer box gears modded??

[Lewy]

G'day

Yer I have 43% reduction gears. And the 5th is from marks adaptors and is about 20% higher. I don't care to correct my speedo I'm simply after better of the mark go and fuel.

Lewy.

[MudRunnerTD]

G'day

Yer I have 43% reduction gears. And the 5th is from marks adaptors and is about 20% higher. I don't care to correct my speedo I'm simply after better of the mark go and fuel.

Lewy.

With the reduction gears i think going to 4.6s will be painful. but really depends how you use it offroad?? 4.3s will give you a good launch off the mark and still see you reving just over 2000rpm on the hwy hopefully. Your current revs are in a terrible spot in the rev range for teh standard turbo, its struggling to make boost there and will be disliking the hills on the free way.

[Lewy]

Yer that's it. Right now it's bloody crap!! At 100 it's struggling bad and the egt is getting way too hot that I either have to be going at 115ish or go back to 4th! I think the 4.3s will have to do. Cheers for every ones help.

Lewy.

[BigRAWesty]

What size tyres are they? Can you bolt some stockies on to see if the ratio change will make it better??

[Lewy]

I am running MTZ's 285/75/16s. No I sold my standed size tyres :-(. So if I was to put standed size tyres on would this give me the same kind of result as putting in 4.3 diff gears? Sorry if that's a silly question but I'm a little clueless on gear ratios lol.

[Lewy]

Derrrr sorry stock tyres will bring back to stock ratio lol derrrr. All good had a brain freeze

[BigRAWesty]

I am running MTZ's 285/75/16s. No I sold my standed size tyres :-(. So if I was to put standed size tyres on would this give me the same kind of result as putting in 4.3 diff gears? Sorry if that's a silly question but I'm a little clueless on gear ratios lol.


Derrrr sorry stock tyres will bring back to stock ratio lol derrrr. All good had a brain freeze

It'll be close as you still have that ratio change in 5th.
Your currently running 33" tyres so you need 1 ratio step to over come that (3.9-4.1) but then you have the 5th gear reduction so you'll need another for that (4.1-4.3).

So I think the 4.3's will be smack on..

Sound right MR??

[nissannewby]

If you carry a bit of weight than 4.3'a will be spot on, however I would be checking your build plate to see what your current ratio is, I am fairly certain most 4.2's were 4.11. 4.6's will be to much unless you want to run bigger Tyres again.

You could also go back to 265's as an option.


My GUIV runs 3.9s too. If I was going to do it it would be 4.3s


With the reduction gears i think going to 4.6s will be painful. but really depends how you use it offroad?? 4.3s will give you a good launch off the mark and still see you reving just over 2000rpm on the hwy hopefully. Your current revs are in a terrible spot in the rev range for teh standard turbo, its struggling to make boost there and will be disliking the hills on the free way.


It'll be close as you still have that ratio change in 5th.
Your currently running 33" tyres so you need 1 ratio step to over come that (3.9-4.1) but then you have the 5th gear reduction so you'll need another for that (4.1-4.3).

So I think the 4.3's will be smack on..

Sound right MR??

I'm guessing so

[Lewy]

Ok great. That does sound the goods. Ok will have to now get it sorted for the 4.3 gears :-))

Cheers guys for all your help and info!!