From: dataprod@nic.cerf.net (Chuck Benson)
Newsgroups: rec.autos
Subject: Re: Jeep Gear Ratios
Date: 6 Jan 1993 19:03:08 GMT
Organization: CERFnet Dial n' CERF Customer Group
NNTP-Posting-Host: nic.cerf.net

In article <1id0tfINNn95@hp-col.col.hp.com> tvervaek@col.hp.com (Tom Vervaeke) writes:
>
>I have a 1991 Jeep Wrangler 4L. It came with 215/75 R15 Goodyear tires.
>After much pondering I decided I would like larger tires to get a little
>more ground clearance. I have installed BF Goodrich All Terrain TA's
>sized 30 x 9.5. They aren't the real huge tires seen on some old CJ's,
>but they are larger.  The car rides fine, and turns fine, but I do have
>a slight problem.
>
>The larger tire circumference (I should measure it) has changed the gear
>ratios of the differentials. I no longer have the acceleration or power
>to make it up large hills without shifting down an extra gear. I forgot
>to take that into consideration. What I need to do is change the
>differentials.
>
>I called the local killer 4x4 shop. They can make me happy - but it will
>cost right around $700 for parts and labor.  This involves installing
>near gearing for both the front and rear differentials, and the labor.
>The product recommended was Dana. This will now also give me
>posi-traction which I did not get as an option on my Jeep when I bought
>it.  The owner says he has a chart that compares tire circumferences and
>original gear ratios to give me what I want. In fact, he claims he can
>recommend several, either right on, a little higher or a little lower
>than original.  He said Dana is a good company and posi-traction is
>definitely recommended.
>
>Any comments? Does the price sound good? Is Dana a good company? ANy
>thing else I should think of? By the way, many folks here at HP have
>used this company (Predator 4-WD - Colorado Springs, CO) and all have
>had positive experiences.
>
>Also, the owner says my original gear ratio will be stamped on the cover
>of my front differential and should be 3.08 or 3.31 if I have the 6
>cylinder. Has anyone else with a Wrangler (also called YJ) looked? I'd
>be interested to find out.
>
>Thanks in advance. Reply here or email. I'll summarize.
>
>
>( ___ )------------------------------------------------------------( ___ )
> | / | Tom Vervaeke           Email:tom_vervaeke@hp0800.desk.hp.com | \ |
> | / | Technology Specialist  Snail: 1900 Garden of the Gods Rd.    | \ |
> | / | Hewlett Packard Co.           Colorado Springs, CO 80901     | \ |
> | / | Colorado Springs, CO   Voice    : 719-590-2133               | \ |
> | / | USA                    Fax      : 719-590-2117               | \ |
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>


        The 30x9.50's work quite well. If your wheel backspacing is
not quite enough, (5") then they may rub the flares at the end of
travel, but flares are cheap. The improvement in traction is enormous.
You will lose stock shocks quite quickly, especially offroad.

        $700 is reasonable for the work described. Before you do it,
you may want to consider whether you want a limited-slip in the front
as well (Power-lock), gear driven limited slips (True-trak), locking
differentials (Lock-rite, aka L.A. Lockers) or air driven lockers
(ARB). I chose ARBs front and rear, but that brings the total close to
$2k.

        The available gearing intervals for your diffs are seperated
by about 10%. That is also about what you have changed the tire size
by. Going up one number should give you back the performance that you
lost.

	Dana is the original manufacturer of the axles in your Jeep.
They are not the only acceptable source for gears, but are certainly
a resonable one.

-- 
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| Chuck Benson | cbenson@dpc.com | (818)887-8173 | Mgr Engr Computer |
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