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diff gears for bigger tyres
https://auszookers.com/forum/viewtopic.php?f=5&t=45679		 Page 1 of 1
Author:  kingkom [ Mon Mar 31, 2014 8:40 pm ]
Post subject:  diff gears for bigger tyres
I realise there are a lot of similar topics and I have done a LOT of other reading and searching however I either get a lot of conflicting info or not quite what I'm looking for.

I have a 2003 manual 2.5 V6 GV and am looking at fitting a 3 inch lift and larger diameter tyres. I'm thinking of going with 245/75/16 (30 inch) MT's

What I can't work out is what diff ratio I have, and what I want to move to. The general consensus on forums is that my stock ratio is 4.3 however when I work it out it looks like 4.6?

And from what I can see I want to be fitting 5.1 diff gears with the 30 inch tyres to have stock engine RPM (2800 at 100km/h).

Anybody have this setup and can let me know if I'm right?
Author:  Sco-tie [ Mon Mar 31, 2014 9:26 pm ]
Post subject:  Re: diff gears for bigger tyres
Yes i would be going for 5.12s if you are going for 245s. The low range in the gvs isn't super low so going a bit lower even with the bigger tyre is a good thing. I have 5.12s with 225/75 and have no problem with revs so with 245s it would be fairly close to stock. You will be wanting a set of 5.12s with a 12 bolt rear when sourcing them. even with 3in lift you will still have scrub on the chassis and inner arch in the rear and on the back of the wheel well with both 225 and 245s
Author:  kingkom [ Mon Mar 31, 2014 11:07 pm ]
Post subject:  Re: diff gears for bigger tyres
thanks mate! would fitting spacers make a difference to any scrubbing? and how often does it scrub? only during flex? or when cornering or anything?
Author:  Sco-tie [ Tue Apr 01, 2014 9:51 pm ]
Post subject:  Re: diff gears for bigger tyres
only on compression in the rear and its minimal not worth worrying about. front scrubs on full lock so u turns and parking but you can feel when it hits so just back off a bit

wheel spacers would stop it rubbing but is illegal and not bearing friendly. best bet is offset rims in the long run. coil spacers will give more ride height but need bumpstop spacers to stop the rear scrubbage. a body lift will also work but as you have air bags thats out. note that the scrubbage above is based on muddies, you will have less or none with ats
Author:  alien [ Tue Apr 01, 2014 10:53 pm ]
Post subject:  Re: diff gears for bigger tyres
FYI wheel spacers and offset rims are equally bad for your wheel bearings, just offset rims are more legal - they're still not entirely legal though as there's limits to the amount of track increase over standard you're allowed...

Now, that said - my current wheel bearings on my sierra are about 2.5 years old and doing fine (just did swivel hubs and the bearings are mint)... they were adjusted to factory specs though, which is the reason for their good life. Previous to that my wheel bearings only lasted me 1 year because the guy that fitted them didn't follow the FSM, so they wore out much faster.

I run 15x7-38mm rims with 31x10.5" tyres... its over 180mm wider than a stock sierra =)
Author:  Sco-tie [ Tue Apr 01, 2014 11:00 pm ]
Post subject:  Re: diff gears for bigger tyres
yes i didnt say that offset was any better for bearing just in the long term they are better than spacers. just an opinion not an answer.
Author:  kingkom [ Wed Apr 02, 2014 5:20 pm ]
Post subject:  Re: diff gears for bigger tyres
Can anyone tell me exactly what's involved in swapping the diff gears? There is like no where in Perth that's done this and they won't give me a quote because they say there may be a lot of fiddling. Do you just swap the ring and pinion over? Whole third member?
Author:  Sco-tie [ Wed Apr 02, 2014 7:14 pm ]
Post subject:  Re: diff gears for bigger tyres
For a GV to fit a locker in the rear you need the rear third member from a vit (12 bolt) to fit it all in (the gv housing is too small to hold it. If you are keeping your diff you can just swap in the R & P. Should be able to have it done for less than $300 if you take the diffs to them.
Author:  kingkom [ Fri Apr 04, 2014 4:12 pm ]
Post subject:  Re: diff gears for bigger tyres
Ok well I don't have time to take out the diffs myself right now because of uni so I was quoted under 600 to swap front and rear third members to vitara ones, are they literally just straight swap? Or is there any modification required? because no one here in Perth really modifies suzukis so none of the diff shops really knew how simple it would be, one place actually quoted me 1800 just for labour. I will be fitting lockers eventually so may as well prep for it now. According to arb you may also need axle shafts? But i was under the impression that all GV was 26 spline heres a pic of what I mean look at the footnote number 3
Image
Author:  tanshi [ Fri Apr 04, 2014 4:18 pm ]
Post subject:  Re: diff gears for bigger tyres
if your going to be putting lockers in get them to put the diff gears when they do that. no point in doing it twice
Author:  tanshi [ Fri Apr 04, 2014 4:19 pm ]
Post subject:  Re: diff gears for bigger tyres
the GV has a different third member to the vitara, thought i think they will fit
Author:  kingkom [ Fri Apr 04, 2014 4:28 pm ]
Post subject:  Re: diff gears for bigger tyres
yeah but I'm putting in a lift kit and getting 245/75/16 tyres now, lockers wont be happening for a year or so, I don't want to drive around for that long with a car that accelerates so slow it's almost undriveable.
Author:  tanshi [ Fri Apr 04, 2014 4:38 pm ]
Post subject:  Re: diff gears for bigger tyres
its your money but thats alot of wasted cash
Author:  henno [ Fri Apr 04, 2014 4:56 pm ]
Post subject:  Re: diff gears for bigger tyres
Yep. Spend an extra ~$1000 to pull both diffs apart a second time just to save a few hundred on (auto)locker/s. Even if you are talking air lockers, it's still a lot of money. It's kid of like rebuilding your bathroom because you need a new bath, but plan on pulling it all apart again in a year to redo the pipes.
Author:  henno [ Fri Apr 04, 2014 4:57 pm ]
Post subject:  Re: diff gears for bigger tyres
Although I do approve of the 'gearing before lockers" mentality.
Author:  Sco-tie [ Fri Apr 04, 2014 5:34 pm ]
Post subject:  Re: diff gears for bigger tyres
For lockers you need the vitara 3rd member in the rear. Same GV axles and a 12 bolt 26sp locker. straight bolt in job
For the front you need a vitara 10 bolt locker and vitara inner axle and cv. If you dont do a locker in the front you can just swap the gearings.
So rear you may as well do with a locker as thats straight forward then you can do the front later. But it's worth doing right the first time rather than paying double labour. Diff shops will often do the labour cheaper if you bring them the gears and diffs off the car. 245s on stock gearings wont be unbearable. if you can handle the 245s and the chopping to fit then you can handle the gearing. Being manual you will have more control over the revs anyway. But if you can get the cash for the lockers within a year i would just do it all at once.
Author:  kingkom [ Mon Apr 07, 2014 5:52 am ]
Post subject:  Re: diff gears for bigger tyres
thanks again for all the advice guys - like i said nobody in perth really does anything to suzukis except for maybe AT's in the stock size and the 35mm iron man or tough dog lift kits and I'm not new to modifying cars but new to fourbies.
so looks like i'm going to just do the 3 inch lift kit and the bigger tyres now - tossing up between 225/75 and 245/75. Then I'll be able to take time to buy the diffs, rebuild them and fit lockers myself and only need to get the diff shop to swap them in.
What did you mean by if i can handle the 245s? Is there a concern other than gearing? Earlier you said the scrubbing was only minimal and on full lock or compression so just wondering if there's anything else I need to worry about? What would I have to chop to fit?
I worked it out and the difference in 5th at 100km/h is only like 225rpm with the 245s so might even save a bit of fuel haha. Otherwise there shouldn't really be much difference should there? I'll just have longer gears - like a lambo.
Author:  Sco-tie [ Mon Apr 07, 2014 6:23 pm ]
Post subject:  Re: diff gears for bigger tyres
You can get any lift kit sent in and fit it yourself pretty easily. Tyres can be shipped in as well. Yes you will have to do some actual cutting with 245s depending on tred pattern where as 225s are just bolt on with minimal scrubbage if any in an at pattern. Only thing you might actually have to chop would be the front and rear part of the base of rear arches and the rear of the front arch and front if you don't have a bar. Only minimal and easily done. If you are fine with that and having better highway economy and lower town economy then 245s are the way to go especially with a 3in lift. As for the diffs I would strongly reccomended you play with them if you know what you are doing and can set the backlash and spacing correctly otherwise your prescious 5.12 will be shrapnel in no time. Check ninjamoses thread at the end for how 245s sit on 2.5in lift + 2in bl
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