Re: JPOR: RE: Suggest a gear ratio for 35-36 inch tires?

[jeff reynolds <rgser@xxxxxxxxxxxxx>]

Date: Wed, 05 Apr 2000 10:52:26 -0700
From: Larry Soo <lars@bc4x4.com>
Subject: Subject: Re: JPOR: RE: Suggest a gear ratio for 35-36 inch tires?

lars wrote:
I've got 35" ProComp muds (actually 34+ inches dia), a 4.0L and 4.10 gears.
With my 33" tires, I found the rpms to be a bit high on the hwy.  The 35's
have taken the edge off.  I'm glad I went 4.10 rather than 4.56 or
numerically higher.  Oh, I have 4:1 tcase gears but I don't think the diff
between 4.10 and 4.56 is particularly noticable offroad.

...lars

<SNIP>

jefe writes:
lars, was this in response to someone's querrie, or is this your own
form of a question?

I found exactly the same symptoms with 33's and 35's. I recently got
my bro's 36x12.5 S.Swamper TSL radials, and they are nuts-on for the
highway, IMHO. They are actually 36.3" tall, one of the few tires
TALLER than advertized. After doing the hammers with them, I found no
appreciably difference with 110:1 crawl, maybe a few percent, but no
noticable difference while crawling. The traction was WAY better than
the Mud Kings ( and that extra inch of clearance didn't hurt either).
The good thing is they turn mid 2K rpms on the freeway. 2500 rpm I
can do for hours on end on the fwy, but 28-2900 rpm does have a nasty
"edge" to it. This is better than 2650rpm  at 65mph and 2900 rpm at
70 mph with my 35" (actually 34.4") Mud Kings. (translation: at
100KPH you would be turning about 2500 rpm with 35's and 4.10's) I
worked out some interesting numbers for comparison to see how much
crawl I would gain by going to shorter gears:
6.69 x 4 x (4.1)=
4.10 gears: 110:1( actually 109.72. I round up)
4.56 gears: 122:1
4.88 gears: 130:1
5.13 gears: 137:1
5.38 gears: 144:1
About a year ago I was thinking of a GV 22% O.D. to "soothe the
savage trannie beast" and close some of those W-I-D-E gaps in the
box. If i had my 'druthers, and could get the right axle gears this
would be a nice set up:
5.13 gears would give you, of course 5.13 final drive in high
range/direct, but the cool part would be the 22% overdrive placing
you right at 4.00 to the rear wheels. (The difference between 4.00
and 4.10 is 2.5%, no biggie), with a tidy 137:1 in creep. This would
work with 35 or 36 in. tires just fine but you would have these great
splits (high range to the rear wheels):
1st:	34.32:1 my current ratios:	27.4:1
1st OD	26.72:1
2nd	17.13:1			13.69:1
2ndOD	14.04:1
3rd	  8.51:1			6.8:1
3rdOD	  6.66:1
4th	  5.13:1			4.10:1
4thOD	  4.00:1

Remember 34.32:1 is lower than some stock 4x4's have in LOW RANGE! (I
think my Scrambler came with a 28.8:1 low range saunter! I can't call
that a crawl range)  and this would be the low gear in high
range/direct. Oh well, just some public meandering for your dining
and dancing pleasure.
regards, as always, jefe