[BFix] Gearing for Best Mileage

[Brian Cooke]

Depends if you want to go a bit slower off road AND if you want to be able to climb any freeway hill in OD.



I ran a 351W with 4.10's and 35" M/T's for close to 8 yrs. I'd shift down (out of OD into 4th) on 6% grades or more to accelerate at all.  Since I have a doubler for low gearing it really doesn't matter what rear end ratio I run for trails but it really does for street.

I ran a 351W with 4.10's and 37" SSR's for 2 years. I still had to shift down on 6% grades or more just to maintain 70mph.

I just put in 4.56 gears with the 37" SSRs (6months now) and I still have to shift down on 6% grades or more!  :)

My buddy runs a very stout 351W stroker, now a 408 with 4.56 gears and 37" M/T's and has to shift down on the same 5 mile long 6% grade. He's dyno'd over 425 HP, so gearing makes a HECK of a difference.

Long story short....     I'd suggest the 4.88 gearing with the ZF and 35" tires.  Especially for lower gearing off road if you aren't running a doubler or equiv.



Brian @ Columbia River Broncos...20 forward gears & 4 reverse to choose from.
  ----- Original Message ----- 
  From: FRANK w 
  To: bfix at broncofix.com ; Ken 
  Sent: Sunday, May 04, 2008 3:07 PM
  Subject: Re: [BFix] Gearing for Best Mileage


  So if you were to keep the 35's all the time would you stay with the 4.56 or would you go with the 4.88. I have a 5.8, ZF 5 speed, 35" tires and getting ready to buy gears. I thought of going with the 4.88's. Thanks.

  Frank 


  ----- Original Message ----- 
    From: Ken 
    To: NHieger at aol.com ; q.dusenberry at comcast.net ; bfix at broncofix.com 
    Sent: Saturday, May 03, 2008 4:21 PM
    Subject: Re: [BFix] Gearing for Best Mileage


    I have a 5.0L Explorer motor and the ZF 5 speed, 4.56 gears and 35" tires. When I drove to VA for the Round up last summer I constantly got 20MPG on the hi-way if I kept the tach below 2500RPM (70MPH) the worst I got was 13MPG and that was traveling at 80MPH. I too thought about going with the 4.88 gears but after driving both on road and off. I'll keep the 4.56 gears and maybe run some 33" street tires for all the around town drive I do.  Last fall I drove about 75 miles from home (150 round trip) to run with some J**p guys and spend 6 hours in low range and only used 7 gal.s of gas. I've never really checked the mileage doing around town driving but I'll have to some day.



    Ken


     
     68 EB 5.0L / ZF 
    35" BFGs / 3" Lift
    4.56 ARB Front & Rear



    ----- Original Message ----
    From: "NHieger at aol.com" <NHieger at aol.com>
    To: q.dusenberry at comcast.net; bfix at broncofix.com
    Sent: Saturday, May 3, 2008 5:23:35 PM
    Subject: Re: [BFix] Gearing for Best Mileage


    FWIW, I have 4:56's in my 77 5.0 sefi/AOD, 35" BFG's. Everything was pretty good when I was running 33's, but now that I am running 35's I kind of wish I had gone with 4:88's. I just seem to be a bit over geared when on long extended climbs at freeway speeds & heading into strong winds. What I need is gear right between 3 & 4th. Having said that if I keep the speeds down (55 or less) I can get around 17 mph.

    Norm

    In a message dated 5/3/2008 11:50:04 A.M. Pacific Daylight Time, q.dusenberry at comcast.net writes:
      Thanks for the reply. That sounds about right to me. 4.56 for 33 with OD and 4.88 for 35 with OD. I'm tempted to go with 4.88’s in the event that I end up with 35’s in the future.









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