Re: RE: Ring Gear changes: 3.55 vs. 3.90

From: Bernd D. Ratsch (bernd@texas.net)
Date: Wed Aug 11 1999 - 10:13:09 EDT


Ok...let me give you a little history on my Dak:

(1) Purchased with 3.55 and 245/70 Tires
(2) Installed 30" BFG's but acceleration sucked
(3) Swapped 3.55's for 3.90's
(4) Lifted the snot out of the truck and installed 32" BFG's
(5) Swapped 3.90's for 4.10's

On the overall scale, your statement it true. What I personally did was
keep a ratio close to the stock one but allow the engine to turn the tires
a little bit easier. My closest estimation is that i'm running 3.60's with
the 32" tires and 4.10 gears. (I actually jacked up the rear end and
counted the driveshaft revolutions compared to one tire revolution.)

- Bernd

At 01:03 PM 08/11/1999 +0000, you wrote:

>Errr, doesn't swapping a 3.55 for a 3.90 w/ bigger tires cancel each
>other out?
>
>3.55's will give decent launch, milage, and towing IMHO
>3.90's will give good launch and towing and half way decent gas milage
>4.10's will give great launch and shitty gas milage
>
>3.55's 215/75/R15 @2000RPM baseline
>3.90's 203RPM more than the baseline to achieve the same speed
>4.10's 311RPM more than the baseline to achieve the same speed
>
>All depends on what you're after but you can't have your cake and eat it
>too! :}
>
>Trevor.
>
>"Bernd D. Ratsch" wrote:
> >
> > Yup...swapped to 3.90's and it made a BIG difference. Mileage didn't go
> > down more than .25 but then again, i'm a little bit of a lead foot. Top
> > speed will suffer slightly but can be made up for with larger tires. (If
> > that's the look you want.) If you're just going for pure acceleration, the
> > 3.90's are the way to go.
> >
> > Ted...how did your truck run after the 3.55 - 3.90 swap?
> >
> > Bernd D. Ratsch
> > Pflugerville, TX
> > 1997 Dodge Dakota SLT/CC - 2WD
> > http://lonestar.texas.net/~bernd/Dakota.htm
> > bernd@texas.net
> >
> > -----Original Message-----
> > From: owner-dakota-truck@buffnet4.buffnet.net
> > [mailto:owner-dakota-truck@buffnet4.buffnet.net]On Behalf Of
> > kwjohn@ais.net
> > Sent: Tuesday, August 10, 1999 8:43 PM
> > To: dakota-truck@buffnet.net
> > Subject: DML: Ring Gear changes: 3.55 vs. 3.90
> >
> > HI all,
> >
> > Anyone who's made this change to a '97+ w/V6, can you give any
> > indication of changes in cruising RPM? How about mileage? Top speed?
> >
> > I'm looking for better acceleration (without load) and pulling power
> > (with horse trailer), and I know this is what's needed. Just trying to
> > understand what to expect. Anyone have a dyno or dragstrip time to show
> > a difference?
> >
> > Thanks
> > Kurt



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