Date: Wed, 24 Mar 2004 16:17:44 -0700 (MST)
From: damian@domain.elided
Subject: [ihc] recommended r&p for a Scout with 36" tires
Hey guys,
I have a dilemma, that I need to resolve before I do something dumb. I
need to upgrade the ring and pinion in my diffs so I can go up hills
again. Since I put on 36" tires on my 77' Scout II it has been having
issues making it up the steep trails. On the bright side I can do 75 MPH
at 2000 RPM, but that's not what a Scout is meant to do. I don't want to
buy a new r&p just to find out it isn't good enough. Here are my specs:
727 Auto Trany (2.45 low)
Dana 20 Tcase (2.00 low)
Dana 44 Diffs (3.54 ratio)
Current Crawl Ratio - a disappointing 17.35:1!
36" x 12.5" x 15" Super Swamper Radial / TSL tires
I was thinking of putting in 4.56's in the diffs, which I think would
bring me to just above stock. I mostly do mud and hill climbs in the
truck, but I need something that I can still do 65 MPH on the highway.
This is mostly an offroad truck, so not too woried about the fuel economy.
Any suggestions? What is a good ratio to use for 36" tires? I just can't
find any good information about this on the net (at least for Scouts).
Damian, gear ratios are part math and part preference. There are ratio
calculators all over the 'net, doesn't matter that they're not
Scout-specific. Depending on the static loaded radius(you need to measure
this) of your tires at normal highway pressures, you have increased the
size of your tires approx 20% over stock(28"-ish). You should do the math
on the actual difference. Using 20% and a straight ratio change from 3.54,
you get 4.425, not an available gearset. Doesn't really matter tho',
because the 36" tires also have a *bunch* more mass to accel/decel. 4.56's
may not even be enough given the usage you describe.