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Gearing Question (again!)

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06 Aug 2018 13:22 - 06 Aug 2018 14:09 #194865 by S200KYS
I was walking the dogs over the weekend, and thinking, as you do...

You know my Gold Jimny is a VVT, and to correct the gearing (for 235/.75/15s) I've fitted earlier ./ non-VVT transfer box and diffs...

So, if someone had an earlier Jimny / non-VVT - is the reverse possible to correct the gearing? i.e. swap the gearbox to a VVT one? Will it fit? And are my gearing assumprions right?

Taking it further... could you do the same and swap the engine for a 1.6 ? i.e. 1.6 Liana engine and a VVT gearbox? Would that fit and work?

Is It Sunday Yet? :)
Last edit: 06 Aug 2018 14:09 by S200KYS.

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06 Aug 2018 16:33 #194875 by Riccy
Replied by Riccy on topic Gearing Question (again!)
as long as its an M series engine, parts seem to be interchangeable (except trying to put a vvt engine into a non vvt car - see James Priestly as he's been having trouble trying that).

I had the R72 vvt gearbox and have changed it to the earlier r7me box. there was some welding on the rear bracket needed. I suspect to get the R72 box into a non vvt jimny would mean altering or moving the chassis crossmember that the rear engine mount goes onto as its further back on the VVT chassis.

Also beware the vvt r72 box is known for bearing failure, making it a weaker choice compared to the older r7me box.

Grimjeeper is the best site ive seen for comparing ratios and the various gearing ratios for the Jimny are in the wiki, bung some numbers in and see what you get!

an example would be for a non vvt jimny wanting to run 31" tyres, just swap the diffs to vvt diffs and its corrected about perfectly, maybe a bit poor in low box tho :laugh:

J999 MNY, M16 VVT, R7me gbox & Rocklobster,
31x10.5r15 Cooper STT, 2x ARB Lockd' 3.9 diffs & twin compressor,
6.5" total lift, Zookbob HD steering shock, Ignis recaro's
Custom bar & arches, rocksliders & guards,
Snorkel, K&N, 13500lb Winchmax, Buzzweld, etc, etc

Plus ULYSSES (06' trayback project)

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06 Aug 2018 20:46 #194881 by S200KYS
Replied by S200KYS on topic Gearing Question (again!)
Hmmm, thanks Riccy ;)

Dave

Is It Sunday Yet? :)

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06 Aug 2018 21:46 #194883 by yakuza
Replied by yakuza on topic Gearing Question (again!)
Partly due to the gearing the R72 is weaker. You put more of the torque to be transmitted by the gearbox when more of the gearing has to be done by it.
I would not recommend the R72 to anyone. after the noise became apparent it was just 15km and it seized. The boxes from 2005 to approx 2009 are the worst. The ones after that have better closed bearings.

For me it was both cheaper and easier to just swap the transfer gears to 17%/87%. By doing so I also moved roughly 17% more torque over to the transfer box from the gearbox so hopefully my second gearbox will now live longer than my first one did..

2005 Jimny M16A VVT, 235 BFG MT, 2" Trailmaster, 17%/87% high/low gears.

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10 Aug 2018 09:37 #194968 by Busta
Replied by Busta on topic Gearing Question (again!)
VVT diffs and a 1.6 is a good combination in a pre-VVT Jimny. It gives a small gearing reduction and a noticeable increase in power.

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15 Aug 2018 10:43 - 15 Aug 2018 10:44 #195140 by S200KYS
Replied by S200KYS on topic Gearing Question (again!)

Riccy wrote: an example would be for a non vvt jimny wanting to run 31" tyres, just swap the diffs to vvt diffs and its corrected about perfectly, maybe a bit poor in low box tho :laugh:


Doing some maffs on that...

The optimum size would appear to be a 30"x9.5" tyre, which is a good size for a Jimny? :)

earlier Non-VVT diff "final drive" ratio is 3.909
later VVT diff final drive ratio is 4.33
So 4.33 / 3.909 = 1.1077

Looking at tyres -

Standard 205/75/15 = 682.5mm diameter
235/75/15 = 727.50 diameter, so 727.50 / 682.5 = 1.0659 a bit low
31"x10.5" = 775 diameter, so 775 / 682.5 = 1.1355 a bit high
So, 30"x9.5" = 750 diameter, so 750 / 682.5 = 1.0989 ... about right ? B)

Is It Sunday Yet? :)
Last edit: 15 Aug 2018 10:44 by S200KYS.

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15 Aug 2018 16:59 #195149 by Riccy
Replied by Riccy on topic Gearing Question (again!)
Yes indeed thats spot on for 30" then (I quoted 31" as thats the most common question I get asked about).

As I said tho, Low box is not low enough for serious stuff or using with lockers really, RW has the answer there

I have a nice pair of vvt diffs here if you want to try it sometime as well as a prop for connecting an R72 gearbox to a SJ t-box that maybe handy ;-)

J999 MNY, M16 VVT, R7me gbox & Rocklobster,
31x10.5r15 Cooper STT, 2x ARB Lockd' 3.9 diffs & twin compressor,
6.5" total lift, Zookbob HD steering shock, Ignis recaro's
Custom bar & arches, rocksliders & guards,
Snorkel, K&N, 13500lb Winchmax, Buzzweld, etc, etc

Plus ULYSSES (06' trayback project)

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15 Aug 2018 17:46 #195153 by S200KYS
Replied by S200KYS on topic Gearing Question (again!)
But the low ratio of a 'standard' Jimny would be retained?

Hmmm...

Is It Sunday Yet? :)

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