> I have heard that one shouldn't need more than 100:1. Remember that the
> lower the gearing, the more torque to the wheels, and we all know how
> Rovers like breaking half shafts. At least I do ;)
My low range first is 70:1 at the axle (T-18 gearbox with granny first,
series transfer case, 4.7:1 ring & pinion)
I have found 70:1 to be too low for most applications and have never
needed anything lower. Because of the torque multiplication I only use
the hand throttle in that gear. Just the slightest foot movement
brings on a strong jerk.
On the other hand I do recall the stock factory low range first as
being too high for many semi technical off road situations.
So, if the late series first low range ratio is too high (40.7:1) and
the Green Rover's ratio is too low for most uses (69.8:1) then the one
ton transfer case low range first (56.6:1) might be a very good ball
park figure. The only problem with that transfer case is the high
range under drive ratio. You would need a Roverdrive just to obtain
stock series highway speeds.
My guess that a near perfect low range first gear ratio for a series
rig doing technical rock crawling would be between 55 and 60:1. But
anything using the 109 one ton gearing is best off being a trailer to
trail rock crawler.
>> Since 1st high
>> is about 16:1, I think 4th low should be about 20:1, 3rd 30:1, 2nd
>> 45:1 and
>> finally 68:1.
At the rear axle (Don't forget transfer case high range is an under
drive):
For Suffix C & newer
1st high = 19.88:1 / 40.70:1
2nd high = 12.00:1 / 24.60:1
3rd high = 8.05:1 / low = 16.50:1
4th high = 5.4:1 / low = 11:1
Notice low range third & fourth splits the high range 1-2 and 2-3
ratios and low range 3rd & 4th are the only lower ratios.
For 109 one ton
1st high = 26.46:1 / 56.56:1
2nd high = 15.96:1 / 34.10:1
3rd high = 10.80:1 / low = 23.10:1
4th high = 7.19:1 / low = 15.40:1
Here 3rd & 4th low range are poor splits of the high range gears and of
very little practical use. The other thing to note is the ratios are
quite different from the non one ton ratios and trailing with another
series rig would case the second one in line to always be at the wrong
place on the power curve if they kept together.
Thems basically yer choices if you stay with series gear boxes. And if
you are going to swap in a different gearbox you might be best off
swapping the engine for something with a tad more performance that will
allow you to use off the shelf bell housing and clutch components as
well.
>> The other option is simply to use a granny gear transmission. Boom,
>> low
>> gearing without changing the t-case.
My T18 with granny first coupled to a series transfer case with
Ashcroft high ratio kit is real close to stock series low range second
gear without dropping into low range.
>> These gearboxes make me wonder how
>> much I really need that nice, tightly and evenly spaced gearing I'm
>> used to.
I think that really depends upon where you drive and what power plant
you use.
Those real low ratios are of no use in sand, snow, savanna or mud.
Them's serious rock crawler gears me boy. And if you stay off the
baddest of the 4 diamond rock trails you never have cause to use that
low a ratio.
But I agree the stock ratio is too tall for most rock work and a 55:1
vicinity low range first gear would go a long way to make a series rig
a respectable rock crawler under 95% of rock trail conditions. The
other conditions, well they provide an high oppertunity to test your
roll cage. If you do not have a full roll cage and a willingness to
use it you don't NEED a ratio lower than 60:1
>> Oh, heck, why not dream of the granny NV4500 with the LT230?
>> 100:1 off road and 100 kph at a mere 2688 RPM!!! (Theoretically)
Having the ratios on a web page I just ran the numbers, 87.54:1.
I think that is too low for anything but a very serious purpose built
extreme rock crawling rig.
TeriAnn J. Wakeman
Santa Cruz, California
twakeman@cruzers.com
http://www.cruzers.com/~twakeman
"How can life grant us the boon of living..unless we dare"
Amelia Earhart 1898-1937
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