MN diff ratio change

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MN diff ratio change

Postby Bikebear on Sun May 15, 2016 4:14 pm

I feel the MN 2.5 diesel is a little overgeared and I'd like to change the final drive ratios from 3.917:1 to 4.3:1, as used in the 3.5L petrol ML. I'm well aware that the engine will rev higher for the same speed and it may affect the fuel economy, that doesn't worry me greatly.
Does anyone know if the 4.3 gears from an ML will go into a 2013 MN 2.5 diesel?
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Re: MN diff ratio change

Postby Cowboy Dave on Sun May 15, 2016 5:32 pm

yes, provided you have the 9.5" diff
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Re: MN diff ratio change

Postby triton_guru on Sun May 15, 2016 5:36 pm

Could you just buy the whole diff assembly and just bolt it in? Or are the pinons different lengths? Might need the 3.5l tailshafts also :)
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Re: MN diff ratio change

Postby 4wd26 on Sun May 15, 2016 5:44 pm

Yeah just easier to swap out whole rear diff
Too much effort swapping out centre axles and ratios even though it can be done if the housing is different
Front diff is the same between models
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Re: MN diff ratio change

Postby snakesoup on Tue Jun 28, 2016 1:30 pm

ok what about putting ml 4.1s into a manual mn with 3.9s in it, if I change the diffs over how much difference will this make, would have to help running 33inch tyres I would think ? sure there would be a formula hey ?
didn't SRB do this to his clubby??
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Re: MN diff ratio change

Postby L200Shogun on Tue Jun 28, 2016 3:10 pm

60mph 29.5" tyres 3.917 give 2141 revs

60 mph 30.6" tyres 4.1 give 2161 revs

so with 4.1 and 31s you will have same gearing as standard

60mph 32.6" tyres 4.33 gives 2142 revs

so with 33s you want 4.3 to have standard gearing

http://www.differentials.com/technical- ... calculator

or

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Re: MN diff ratio change

Postby snakesoup on Tue Jun 28, 2016 6:28 pm

excellent work there little shogun!!
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Re: MN diff ratio change

Postby Maxiy on Wed Mar 13, 2019 12:01 pm

Quick Question

What size diff would a 2014 MN have? 9.5 inch ?

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Re: MN diff ratio change

Postby aids84 on Wed Mar 13, 2019 3:30 pm

Yes more than likely a 9.5" they have 12 bolts holding the centre into the housing. The 9" only had 10 bolts.
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Re: MN diff ratio change

Postby Maxiy on Thu Mar 14, 2019 5:46 am

aids84 wrote:Yes more than likely a 9.5" they have 12 bolts holding the centre into the housing. The 9" only had 10 bolts.


Cheers.

Next question.
If i get new 4.3 centres, will they just bolt in, or will i have to change the gears on the ends of the drive shafts (please excuse my ignorance)
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Re: MN diff ratio change

Postby aids84 on Thu Mar 14, 2019 6:17 am

The rear diff centre will swap straight over.

You could swap the entire front diff assembly out of a V6 ML into your car and run a vacuum line to the actuator to keep it locked in. Or takes the gears out and get a diff specialist to install the gears into your housing and do away with the actuator setup.
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Re: MN diff ratio change

Postby Maxiy on Tue Jul 02, 2019 7:05 am

Me again

Having trouble finding the front 4:3 diff from a V6 ML, but seem to be able to find heaps of cheap front 4:3 diffs from NM-NP pajeros.

Will the pajero diffs fit into a triton? and will they work with a 4:3 rear diff from an ML ?

(i know on paper they should work as the gearing is the same, but i'm no mechanic so there may be some hidden difference i dont know about)
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Re: MN diff ratio change

Postby Maxiy on Tue Dec 24, 2019 9:30 am

Hi all
Managed to pick up a set of ML 4.3 diffs. Can anyone recommend a good place to buy replacement seals and gaskets?
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Re: MN diff ratio change

Postby Maxiy on Fri Jan 03, 2020 1:07 pm

Hi all.
As above I have managed to get a set of 4.3 ml diffs.

As I understand when the actuator is out (shaft towards the wheel) it is engaged in 4wd, and when the shaft is in (towards the diff) it is engaged in 2wd correct?

If the above is correct, my next question is. Do I need to actually retrofit vacuum lines considering the default position of the actuator is 4wd? Or will it try jump out of 4wd of there is no force keeping the shaft in the out position. ?

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Re: MN diff ratio change

Postby Maxiy on Tue Mar 10, 2020 4:03 pm

Hi All

Didn't get much feedback on the above questions, so I just dove in and installed them and watched what happened :lol:

Anyway, the install was pretty straight forward, simple bolt off the old and bolt in new. The front was definitely harder than the back, as you had to remove the CV shaft from the housing on the passenger side of the diff, this involved removing the knuckle assembly so the CV could slide out far enough. The driver's side simply bolts off the flange plate on the diff housing.

Rear was very straight forward, remove wheel, then drum, disconnect ABS sensor and brake lines, then unbolt and slide drive shafts out. Then you just unbolt the driveshaft and the center and out it comes.

Then bolt everything back in and job done.

So as per my previous posts, the ML front housing has a vacuum actuator that engages the diff. From my investigation, the default position of the actuator shaft has the diff in the ENGAGED position, so simply not hooking up the actuator means the diff is engaged and is ready for input from the transfer case. So i did not hook up the actuator, and 4x4 seems to work perfectly. My 1 concern is that the shaft may want to jump out when the front diff is under load, so i will have to do some offroad work and test this.

1 surprise i had with the install, is that i realized the rear diff is actually an LSD. I have no idea if this is going to cause any conflict, or problem with the traction control, but so far it seems fine. Time will tell

ANyway quick update for those who are interested.
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Re: MN diff ratio change

Postby SexyEggy on Thu Nov 19, 2020 6:57 am

Hey Maxiy,
Looking at doing this myself some time soon so you found it was easier to do a full swap of the diff assembly rather than just changing the centers out ?
Cheers
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Re: MN diff ratio change

Postby srb on Fri Nov 20, 2020 5:03 am

You'll have no issue with that actuator jumping out, it's a "normaly closed" meaning it requires vacuume to open into 2wd. Just blank off the vacuume port so it doesn't fill with crud.

As for the LSD, this has been done before and there was no issues with traction control systems. Apparently it works very well, best of both worlds.

How does the 4.3 ratio feel? What tyre size you running with?

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Re: MN diff ratio change

Postby Maxiy on Fri Nov 20, 2020 11:18 am

SexyEggy wrote:Hey Maxiy,
Looking at doing this myself some time soon so you found it was easier to do a full swap of the diff assembly rather than just changing the centers out ?
Cheers


I did the full front housing (they are generally sold from the wrecker this way, cause the whole thing easily bolts out) and i did the rear centre.
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Re: MN diff ratio change

Postby Maxiy on Fri Nov 20, 2020 11:21 am

srb wrote:You'll have no issue with that actuator jumping out, it's a "normaly closed" meaning it requires vacuume to open into 2wd. Just blank off the vacuume port so it doesn't fill with crud.

As for the LSD, this has been done before and there was no issues with traction control systems. Apparently it works very well, best of both worlds.

How does the 4.3 ratio feel? What tyre size you running with?

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Good to know, i have had no issues so far, though i have not blocked the vaccum inlets :oops: probably should do that.

love the 4.3's, has given me my low end back, and has made a surprising difference to engine temps. Much easier towing also.

Running 32's at the moment, 33's to go on shortly
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