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5.12 and 33's
5.12 and 33's
i have looked at this thread from the bible ( http://www.outerlimits4x4.com/PHP_Modul ... 236#584236 ) and if i have worked it out right 5.12 ratios would be about right for 33" tyres. Am i correct in assuming this? if this is correct does anyone have a spare set of 5.12 diff gears they dont want (i already have one set)
Last edited by flyinwall on Tue Jul 08, 2008 9:51 pm, edited 1 time in total.
R.I.P. Darryl "DAZZA" Mutch 02/08/1978 - 26/08/2012 aged 34 years ... You will be missed my little brother.
http://www.outerlimits4x4.com/viewtopic.php?f=16&t=39190&start=150
http://www.outerlimits4x4.com/viewtopic.php?f=16&t=39190&start=150
You're about right for the road.
Off road 33's will need more gearing than 5.12's alone due to the added traction, weight and drag of the bigger tyre.
Steve.
Off road 33's will need more gearing than 5.12's alone due to the added traction, weight and drag of the bigger tyre.
Steve.
[quote="greg"] some say he is a man without happy dreams, or that he sees silver linings on clouds and wonders why they are not platinum... all we know, is he's called the stevie.[/quote]
You'll ned up wanting transfer gears eventually.
Crawl ratio you're proposing:
3.65X2.55X5.12= 47.6
Unless you're running mud only and a 1.6EFI or something, that's going to suck on 33's. IMHO even 60:1 is marginal for 33's in my book.
with NT diff gears and a 4:1 case:'
3.65X4.1X3.9=58.3
With 5.12's
3.65X4.1X5.12=76.6 - sweet unless your into the super technical stuff
with a 6:1
3.65X6.4X3.9=91.1
with a 5.12's
3.65X6.4X5.12=119.6
with a 33 or so, that 91:1 figure will be pretty good and NT diffs are much cheaper/easier to get than 5.12's (and stronger)
With 33's, you'll run about 3300rpm with this setup @ 100kph in 5th. MArginal for a 1.3 but easy for something with more torque. That's with a TT gearset, with something with a shorter high range, (like the series 4 RH) you'll be pretty close to stock at 100kph in 5th.
I run 5.12's but I don't think they are any substitute for transfer gears for a car that's used offroad.
Steve.
Crawl ratio you're proposing:
3.65X2.55X5.12= 47.6
Unless you're running mud only and a 1.6EFI or something, that's going to suck on 33's. IMHO even 60:1 is marginal for 33's in my book.
with NT diff gears and a 4:1 case:'
3.65X4.1X3.9=58.3
With 5.12's
3.65X4.1X5.12=76.6 - sweet unless your into the super technical stuff
with a 6:1
3.65X6.4X3.9=91.1
with a 5.12's
3.65X6.4X5.12=119.6
with a 33 or so, that 91:1 figure will be pretty good and NT diffs are much cheaper/easier to get than 5.12's (and stronger)
With 33's, you'll run about 3300rpm with this setup @ 100kph in 5th. MArginal for a 1.3 but easy for something with more torque. That's with a TT gearset, with something with a shorter high range, (like the series 4 RH) you'll be pretty close to stock at 100kph in 5th.
I run 5.12's but I don't think they are any substitute for transfer gears for a car that's used offroad.
Steve.
[quote="greg"] some say he is a man without happy dreams, or that he sees silver linings on clouds and wonders why they are not platinum... all we know, is he's called the stevie.[/quote]
Re: 5.12 and 33's
you'll love em and you'll have enough gearing for 33's, even better if you had an auto. our group all run diff gears and 33's, some with stock engines too, and they perform ace offroad. 99.5% of the time we use normal low range ( lots of our trucks have twins ). go for it, you'll find them RELIABLE.( oh and the other 0.5% is for showing off). pm me if you want more details and pics of some of these rigs.flyinwall wrote:i have looked at this thread from the bible ( http://www.outerlimits4x4.com/PHP_Modul ... 236#584236 ) and if i have worked it out right 5.12 ratios would be about right for 33" tyres. Am i correct in assuming this? if this is correct does anyone have a spare set of 5.12 diff gears they dont want (i already have one set)
lwb 1.6efi,4sp auto,f&r airlockers,dual t/cases.custom coils.builder of ROAD LEGAL custom suzukis...and other stuff.
CAD modelling-TECH drawings-DXF preparation.
http://www.auszookers.com/index.php
CAD modelling-TECH drawings-DXF preparation.
http://www.auszookers.com/index.php
Joe and I disagree over this. Joe doesn't like transfer gears because they had a poor reliability record, generally when there was only one supplier to the australian market. I've seen lots let go years ago but it's been a long time since we've had any fail in the club here in vic - about three years since a failure and that was warrantied. (eventually)
We're now all using US supplied gears and haven't had a failure. They're quiet, install easily and they're cheap.
Lets work some numbers out:
Joe likes 5.12's, and it is true that they do offset about a 33' tyre, pushing cruise RPM up to 3900 rpm on the highway with a 33" tyre on an otherwise stock car.
However, the big gain in road gearing doesn't translate into off road gearing. Stock crawl ratio is 29:1 for a WT, and goes to 41:1 with 5.12's in the car, which looks good, but you have to add in the effect of the bigger tyre:
Divide that by tyre diameter:
29/26= 1.11
41/33= 1.24
Your low range is actually only 12% lower than stock. That's not enough. Yes, you can add in a 1.0 transfer case, and now it's another 14% lower than stock, but your road revs rise another 12%, making for 4300rpm at 100kph.
from now on I'll assume a best case of a 1.0 transfer with it's lower gearing.
To counter this lack of low range, Joe (and others - even I was going to do it once) likes to run dual transfer cases. This is a very major modification, as you could imagine. The problem is, vitaras have a very tall low range of 1.81:1
So, for the work of dual transfers, you have 4300 road RPM, a 2.55 low range, a 2.87:1 low range, and a 4.6:1 compound low range. That 4.6 compound low range adds up to a crawl ratio of 86.2 Which is sweet, but possibly the most amount of work ever to gear a 33 on a sierra.
Of course you could use a 4.6 or something in the diffs to lower cruise revs, but then the crawl goes to 77:1 and cruise revs drop to 3900 rpm or so. Again, a lot of work for less gearing than a 4.9 transfer set.
The major selling point of the duals is that your stock 2.55 low range is retained for easy driving. That's fine, and sometimes i'd like an intermediate step, but I'm much lower overall (6.51 transfer) so I don't get much speed out of low range at all - about 20kph. do I think it's worth all the work of duals? If I had a 4.7 low range, I'd never need an intermediate, taller step.
Joe already knows all this though, which is why he likes AW-4 autos. These have a taller 4th gear to lower those cruise revs, and the 2.4:1 converter ratio means the 4.7 low range is absolutely all you ever need. this adds even more work and $$$ to the solution. Thing is, there's no need for the second transfer once you have the AW-4 - with 5.12's and a 1.0 transfer, the effective crawl ratio is 94:1 anyway.
Of course, if you're convinced transfer case gears will keep failing, then duals look feasible; but it's not really the case any more.
Steve.
We're now all using US supplied gears and haven't had a failure. They're quiet, install easily and they're cheap.
Lets work some numbers out:
Joe likes 5.12's, and it is true that they do offset about a 33' tyre, pushing cruise RPM up to 3900 rpm on the highway with a 33" tyre on an otherwise stock car.
However, the big gain in road gearing doesn't translate into off road gearing. Stock crawl ratio is 29:1 for a WT, and goes to 41:1 with 5.12's in the car, which looks good, but you have to add in the effect of the bigger tyre:
Divide that by tyre diameter:
29/26= 1.11
41/33= 1.24
Your low range is actually only 12% lower than stock. That's not enough. Yes, you can add in a 1.0 transfer case, and now it's another 14% lower than stock, but your road revs rise another 12%, making for 4300rpm at 100kph.
from now on I'll assume a best case of a 1.0 transfer with it's lower gearing.
To counter this lack of low range, Joe (and others - even I was going to do it once) likes to run dual transfer cases. This is a very major modification, as you could imagine. The problem is, vitaras have a very tall low range of 1.81:1
So, for the work of dual transfers, you have 4300 road RPM, a 2.55 low range, a 2.87:1 low range, and a 4.6:1 compound low range. That 4.6 compound low range adds up to a crawl ratio of 86.2 Which is sweet, but possibly the most amount of work ever to gear a 33 on a sierra.
Of course you could use a 4.6 or something in the diffs to lower cruise revs, but then the crawl goes to 77:1 and cruise revs drop to 3900 rpm or so. Again, a lot of work for less gearing than a 4.9 transfer set.
The major selling point of the duals is that your stock 2.55 low range is retained for easy driving. That's fine, and sometimes i'd like an intermediate step, but I'm much lower overall (6.51 transfer) so I don't get much speed out of low range at all - about 20kph. do I think it's worth all the work of duals? If I had a 4.7 low range, I'd never need an intermediate, taller step.
Joe already knows all this though, which is why he likes AW-4 autos. These have a taller 4th gear to lower those cruise revs, and the 2.4:1 converter ratio means the 4.7 low range is absolutely all you ever need. this adds even more work and $$$ to the solution. Thing is, there's no need for the second transfer once you have the AW-4 - with 5.12's and a 1.0 transfer, the effective crawl ratio is 94:1 anyway.
Of course, if you're convinced transfer case gears will keep failing, then duals look feasible; but it's not really the case any more.
Steve.
[quote="greg"] some say he is a man without happy dreams, or that he sees silver linings on clouds and wonders why they are not platinum... all we know, is he's called the stevie.[/quote]
don't worry bout the duals..just mentioned that so people won't go "oh, but he has duals". try diff gears you'll like em!
lwb 1.6efi,4sp auto,f&r airlockers,dual t/cases.custom coils.builder of ROAD LEGAL custom suzukis...and other stuff.
CAD modelling-TECH drawings-DXF preparation.
http://www.auszookers.com/index.php
CAD modelling-TECH drawings-DXF preparation.
http://www.auszookers.com/index.php
ok i guess i should have said this before but i have a toyota 4k and 5sp (3.789 1st gear) 1lt case and 4.1 diff gears at the moment but i am considering putting the 5.12 diff gears in just to regain the drivability
and this would be the cheapest option by far (i love it when mechanics are mates)
and this would be the cheapest option by far (i love it when mechanics are mates)
R.I.P. Darryl "DAZZA" Mutch 02/08/1978 - 26/08/2012 aged 34 years ... You will be missed my little brother.
http://www.outerlimits4x4.com/viewtopic.php?f=16&t=39190&start=150
http://www.outerlimits4x4.com/viewtopic.php?f=16&t=39190&start=150
4.1's would be 1 litre diffs from memory .. 5.13s wont fit in them as they are larger.flyinwall wrote:ok i guess i should have said this before but i have a toyota 4k and 5sp (3.789 1st gear) 1lt case and 4.1 diff gears at the moment but i am considering putting the 5.12 diff gears in just to regain the drivability
and this would be the cheapest option by far (i love it when mechanics are mates)
" If governments are involved in the covering up the knowledge of aliens, Then they are doing a much better job of it than they do of everything else "
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