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Gearing: 4.56, 4.88, or 5.13

Best Gear Ratio for 80% trail, 20% street on 37” tires

  • 4.56

    Votes: 0 0.0%

  • 4.88

    Votes: 6 19.4%

  • 5.13

    Votes: 25 80.6%
  • Total voters
    31
Gibby56

Gibby56

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I have been playing with gear ratio calculators a ton but would love some real world feedback.

I am planning on going through the axles early next year and am starting to compile parts. Curious to hear what gears you guys are running in rigs that are primarily trail use. The K5 will be towed to the general area of the trails but will be driven to the trailhead. Last rig had 6.17’s and 41’s but not enough power to hit 5th gear. The Blazer has the extra 4 cylinders that one was missing.

Current Drivetrain: 350, 4L60 (700R4), NP241, D60/14BFF with 4.10’s, 37’s

Planning to stay 37’s on this one

What is your experience with any of these ratios? Any regrets?
 
sweetk30 said:
700r4 = as deep as you can .

and with the 37" tire and 700r4 and deep gears highway driving will still be real good and lots of power .
Click to expand...
That is what I gathered from the gear ratio calculators. Seems like 65mph would put me barely over 2k rpm. Pretty much the sweet spot for the 350. Needed a gut check to make sure everything in theory works that way in the real world.

Would like to hear some more opinions/experiences before I order gears!
 
Gibby56 said:
Have you been happy with 5.13’s?
Click to expand...

yes they've been great however I wish I had the 4th gear (4L80E) sometimes on the freeway. If you need someone to setup your gears I would recommend driving up to Sac to River City Differential. He's a good guy, affordable and a wheeler....
 
skunked said:
yes they've been great however I wish I had the 4th gear (4L80E) sometimes on the freeway. If you need someone to setup your gears I would recommend driving up to Sac to River City Differential. He's a good guy, affordable and a wheeler....
Click to expand...

Thanks for the recommendation! I’ll reach out when the time comes.

What T Case are you currently running?
 
5.13's aren't nearly as drastically low as popular opinion would have you believe, too many people are used to the under geared feel of a 3.08/3.42 on 35's (or bigger) and think that just because it moves and can spin a tire in 4 low it's fine. I've run 4.56's and 5.13's on 38"+ tires and, imo, 4.56's are "adequate". Nothing wrong with a 4.56 but if you are running anything bigger than a 35" tire and especially if you have overdrive then 5.13's or even 5.38's would be a great choice.
 
I have 33" a 700r4 and 4.10, I ordered 4.88 after towing my little dune buggy. 50 mph is 1500 rpms to low to accelerate up a shallow grade w/o down shifting to third. 4.88 should put me at the bottom of my torque curve @55ish.
You might even consider 5.33s.
My Son's F250 has 4.56 w/ 37s a np435 2nd gear starts are a little soft.
 
Gibby56 said:
I have been playing with gear ratio calculators a ton but would love some real world feedback.

I am planning on going through the axles early next year and am starting to compile parts. Curious to hear what gears you guys are running in rigs that are primarily trail use. The K5 will be towed to the general area of the trails but will be driven to the trailhead. Last rig had 6.17’s and 41’s but not enough power to hit 5th gear. The Blazer has the extra 4 cylinders that one was missing.

Current Drivetrain: 350, 4L60 (700R4), NP241, D60/14BFF with 4.10’s, 37’s

Planning to stay 37’s on this one

What is your experience with any of these ratios? Any regrets?
Click to expand...
I had a k5 with 37" tires, 350 tbi th350 and 203/205 doubler and 4.88 gears.
It was perfect for trails but going anything more than 60mph was too much rpms, so I tossed a 700r4 and it's fine up to 75 mph and better first gear
 
Thanks for all the feedback fellas! Happy to hear the reality of 5.13+ is as good as it seems
 
Before the rebuild I'm currently working on........I had 350 TBI, 700R4, NP241, D60, 14BFF, 37's and 5:13s. Perfect combo IMHO. Cruised 80 mph for 2 hours....perfect rpms and no issues. When wheeling at Moab......having it in low and going down a steep hill felt like I was on the brakes. And I wasn't. I'd do the same set up again if I were to run that tire size.
 
I've been on 4.88 for years on various 37" and 38" tires. Never once wished for 4.56, but often think about 5.13. Only 2 downsides:
- The weaker pinion gear if you have an 8.5" diff.
- Any driveline issues (bad pinion angle or no C/V) get worse as gears get lower.

As you get to bigger tires, 80MPH isn't going to happen except very occasionally anyway. Might as well have the performance.
 
Fastereddie said:
Yeah if you’re not going to be running a doubler, I’d go 5.13
Click to expand...

Planning to stay with the 241 for as long as it stays in one piece. Thinking about the Atlas 4 with 10.34:1 gearing wayyyyy down the road
 
I would go 5.13 , I would not go lower then that . We have seen multiple failures with 5.38’s the pinion just gets to be to small .
 
It may have been mentioned, but here's a cool rpm/ gear ratio/ speed calculator...

Clicky
 
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