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 I don't understand gear ratios; anybody able to help? 
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Bomb Hole Digger
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Post I don't understand gear ratios; anybody able to help?
I have a 2004 (54 plate) Grand Vitara with the pug RHW 2.0 TD fitted. I've modified it a bit and stuck tyres on which are the equivalent to around 31".
It would be fair to say that it is pretty sluggish now, it wasn't very pokey in the first place, but since the tyres have been fitted, I can barely get it over 2000 rpm when cruising and it dies going up hills.

I fitted a CR-Tech tuning chip to try and give it a bit more torque, and that has made a difference, but not enough really.

So I've started looking at changing the gearing. I can fabricate all sorts of things and I'm pretty handy with a set of spammers, but I totally have no idea about gear ratios.
I don't know what my truck is likely to have fitted now, how to even tell, and I don't know what I need to fit to make it more drivable, higher or lower ratios?

Can anybody give me a clue so that I don't waste a load of time and money learning by making mistakes please?

Many thanks, Alan


Sat May 30, 2015 7:40 am
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Post Re: I don't understand gear ratios; anybody able to help?
Righto.

You need to google your model of truck, that should tell you what ratios are fitted; probably 4.3:1

You'll need to replace the front and rear diff units, which is a pretty easy job.

The good news is that with either a 4.8:1 or even 5.12:1 diff you should get back close to stock. have a look for a gearing calculator to help you out.

both the above diffs were very common in SWB vitaras. You have 26 spline front shafts, so you might be stuck with 4.8 diffs, as most of these were 26 spline, and found on 1996-2000 swb vitaras.

you may also have to get the front diff built into your front steel housing, as the steel housings are stronnger.

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mud and diesel wrote:
...turns out ive got a robins nest in my overalls, with a chick in so im going to have to leave the little sod for the next 2 weeks


Sat May 30, 2015 9:16 am
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Bomb Hole Digger
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Post Re: I don't understand gear ratios; anybody able to help?
Thank you mate, that's a good start. I'll suss out what I can from the internet regarding my gearing and see if I work the rest out from that.

Quick additional questions,

1. Is building the new gearing into my steel diff a straightforward job, or does it need to be done professionally with special equipment?

2: Why does the spline count matter on the drive shafts? I know mine is 26 splines, but if I fitted the crown-wheel and gubbings from a better ratio'd diff, would it change my shaft relievers too?

Sorry if I sound dim, I really haven't ever touched the inside of gearbox or diff


Sat May 30, 2015 10:07 am
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Mud Mad
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Post Re: I don't understand gear ratios; anybody able to help?
ideal_dog wrote:
Quick additional questions,

1. Is building the new gearing into my steel diff a straightforward job, or does it need to be done professionally with special equipment?


You probably will need a dial indicator but that is about all. here are a few links to rebuilding articles that will give an idea of how difficult the job is:

http://acksfaq.com/yukoninstmanual.htm
http://acksfaq.com/samuraiDifrebuildFSM.htm
http://www.zukikrawlers.com/showthread.php?t=4215

Although the above links talk about the SJ413 (Samurai/Sierra) differential, they are almost identical to that of a Vitara differential.


ideal_dog wrote:
2: Why does the spline count matter on the drive shafts? I know mine is 26 splines, but if I fitted the crown-wheel and gubbings from a better ratio'd diff, would it change my shaft relievers too?


The spline count is important if you use a differential out of a Vitara (like a short wheelbase unit) that uses an axle shaft with a different spline count than your vehicle. If the spline counts are different, you will not be able to slide the axles into the differential's sidegears. Oops.

Ideally you want to find a set of differentials with the ratio you want that fit on the same vehicle model and year that you have. This would allow you to simply install the new differentials (housing and guts) with no modification at all!

Unfortunately, that may not be an option as not all Vits had the same available gear ratios and the spline count changed at least once during production. In that case, you would have to remove the new differential sidegears and install the old sidegears that have the proper spline count. It has been a while since I did this, but I think that you can actually swap out the sidegears without actually tearing down the differential - which would save lots of time and money!

Time to do research into differential types used on various Vits during various manufacturing years with different spline counts. Here is a table for North American Sidekicks and Trackers (what you call Vitaras) that might help a bit:

http://bbs.zuwharrie.com/content/topic,15579.0.html


I hope that this helps!


Sat May 30, 2015 10:59 pm
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Bomb Hole Digger
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Post Re: I don't understand gear ratios; anybody able to help?
That does help a lot, thank you very much :-bd

Time for some in-depth research. It's about time I got my head around this anyway!

Alan


Sun May 31, 2015 7:49 am
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Post Re: I don't understand gear ratios; anybody able to help?
I'd get you gears built into your front housing by a pro - it's not the easiest thing in the world.

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mud and diesel wrote:
...turns out ive got a robins nest in my overalls, with a chick in so im going to have to leave the little sod for the next 2 weeks


Sun May 31, 2015 2:45 pm
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Bomb Hole Digger
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Post Re: I don't understand gear ratios; anybody able to help?
If I do end up swapping gears in, I think I will most likely get some help with it. I haven't got half of the kit needed according to Ack's links, so it might work out cheaper to get the help of somebody with the right tools.

Right now though, I've started considering a pair of Hilux, or similar, axles, and doing a live front axle with matching rear. If I could find the page I was reading this morning I would tell you what ratio the Hilux apparently has. What I read was that somebody fitted them because they wanted to do a live axle conversion anyway, but as a bonus it turned out the ratios sorted out the gearing problems caused by them having 33's fitted.

I just need to be sure of the ratios being suitable, the axle widths being suitable, and the cost and availability of the axles. If all that checks out, I might well go down that route.


Sun May 31, 2015 3:26 pm
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Post Re: I don't understand gear ratios; anybody able to help?
Plus the cost & hassle of an IVA.

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mud and diesel wrote:
...turns out ive got a robins nest in my overalls, with a chick in so im going to have to leave the little sod for the next 2 weeks


Sun May 31, 2015 6:12 pm
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Bomb Hole Digger
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Post Re: I don't understand gear ratios; anybody able to help?
That's a good point Munkee, this truck isn't an off road only truck, and as I drive the family around in it, it needs to be legal. Maybe I'll settle back into the gear set change idea :roll:

Thanks for reminding me :-bd

- Post below merged at Sun May 31, 2015 7:03 pm - Please edit rather than double posting within 1 hour of last post - Admin -

Done some Googling and it seems very likely my GV does have a 4.3:1 gear ratio as I was told it probably did.

There does seem to be quite a few SWB Vits being broken, the ones which will probably have 4.8:1 ratios and 26 splines. Is that gearing common to all the engine variants or specific ones?
Also, the 5.12:1 ratio diffs which are probably 22 spline up front; which model Vitara had them in, and are all the back axle diffs compatible, by that I mean, the fronts need to be right because of the spline count, do the backs all have the same mesh gears?

Sorry for so many questions. :ymblushing:

- Post below merged at Sun May 31, 2015 7:39 pm - Please edit rather than double posting within 1 hour of last post - Admin -

Some more digging has found the information in this link: http://suzuki-grandvitara.info/cms/content/view/72/64/

Can somebody have a look please and tell me if it's saying that my GV actually has a 3.9:1 ratio? I might not be reading it correctly!


Sun May 31, 2015 7:39 pm
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Post Re: I don't understand gear ratios; anybody able to help?
4.8s were on MOST swb 1.6 made between 1997 & 2000.

5.12s were on most 1.6 manual vits prior to that.

lift ONLY one rear wheel, and accurately spin it one full rotation, whist carefully counting how many times the prop spins. divide your answer by 2, and that will tell you your diff ratio.

In your case, less than 8 prop rotations will mean 3.9, over 8.5 rotations will be 4.3.

Yes, that is a 100% accurate way of telling.

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mud and diesel wrote:
...turns out ive got a robins nest in my overalls, with a chick in so im going to have to leave the little sod for the next 2 weeks


Sun May 31, 2015 8:48 pm
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Bomb Hole Digger
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Post Re: I don't understand gear ratios; anybody able to help?
Fantastic, I'm off work Wednesday, I'll give that a go.
Thank you!


Sun May 31, 2015 9:43 pm
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Post Re: I don't understand gear ratios; anybody able to help?
Does yours have ABS...?

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mud and diesel wrote:
...turns out ive got a robins nest in my overalls, with a chick in so im going to have to leave the little sod for the next 2 weeks


Mon Jun 01, 2015 4:57 pm
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Post Re: I don't understand gear ratios; anybody able to help?
Yes mate it does. I've got to strip the near-side half shaft out anyway because the previous owner had a wheel bearing collapse and debris got down the tube and damaged the ABS ring, so now I've got issues with it and have to have the ABS disconnected so I can drive the car, but that puts the ABS and Brake warning lights on.

Why do you ask if mine has ABS?

Alan


Mon Jun 01, 2015 5:17 pm
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Post Re: I don't understand gear ratios; anybody able to help?
I had a diff that had a sensor wheel on it, but it's quite possible that was for some other reason. If your sensors are on the hub, ignore me :)


(I've never had a zook with ABS....)

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mud and diesel wrote:
...turns out ive got a robins nest in my overalls, with a chick in so im going to have to leave the little sod for the next 2 weeks


Mon Jun 01, 2015 5:21 pm
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Bomb Hole Digger
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Post Re: I don't understand gear ratios; anybody able to help?
Lol, okay mate.
I've never had one with ABS either as this ones hasn't worked since I've had it, and all previous Suzuki's were SJ's.

The ABS on the GV is inside the axle tube on the rear, on the diff side of the bearing, and on the front it's part of the wheel bearing assembly.

I'm going to be starting my search for a pair of diffs as soon as I've done your ratio test on mine later this week. I'm looking forward to having the truck more drivable I can tell you!

- Post below merged at Mon Jun 01, 2015 5:43 pm - Please edit rather than double posting within 1 hour of last post - Admin -

Just thinking, I wonder if the thing you had on your diff was anything to do with the air activated free-wheeling diff thing GV's are supposed to have?

I'm looking for manual hubs for mine as I've noticed that whether in four wheel drive or not, the front driveshafts still rotate so I imagine they are turning something inside the diff too.


Mon Jun 01, 2015 5:43 pm
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