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4.88 vs 5.13 for 4.0 5-speed

connor grimes

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I know this has been beat to do death but just wanted some clarity before buying gears. It’s been recommended that automatic owners get 5.13 for 35’s, does this hold true for 5 speed owners as well? Currently running 4.56 gears 35” tires on Dana 30/35 . Dana 35 has revolution 1541h 30 spline axles with Eaton e locker . Dana 30 is running stock axle shafts no locker. Jeep is my DD that sees rock crawling / over landing 6-8 times a year . What’s the recommended ratio ? Thank you!
 

Jerry Bransford

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I know this has been beat to do death but just wanted some clarity before buying gears. It’s been recommended that automatic owners get 5.13 for 35’s, does this hold true for 5 speed owners as well? Currently running 4.56 gears 35” tires on Dana 30/35 . Dana 35 has revolution 1541h 30 spline axles with Eaton e locker . Dana 30 is running stock axle shafts no locker. Jeep is my DD that sees rock crawling / over landing 6-8 times a year . What’s the recommended ratio ? Thank you!
Since you're surrounded by mountains to get to any wheeling I'd probably go 5.13. I liked my 4.88 gears for the 5-speed and getting up the same mountains with 35's but between the two 5.13 would be a great choice. 4.88 would be too but 5.13 would be real nice going up SoCal's mountain roads and steep highways.
 

Woodrow

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At what gear ratio with a TJ on 35s do you start getting into the critical driveshaft RPM range at freeway speeds (say 80 MPH)?
That seems like an important question for a rig which is primarily daily driven. I know there's a calculator somewhere (Tom Woods had a good one but a quick search failed to pull it up).
 

Jerry Bransford

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At what gear ratio with a TJ on 35s do you start getting into the critical driveshaft RPM range at freeway speeds (say 80 MPH)?
Critical rpms occur at redline. It's happy at any rpm you can stand and happy at rpms you can't stand if they're below redline. I ran mine for several years on the highway (before it was stolen) at 3100-3500 after converting my 5-speed manual with its 4.88 gearing to a 3-speed automatic which had no overdrive.

This gear ratio/rpm calculator is the only one I use, it has all the transmissions pre-stored into it so we can generate the exact rpms we'll get with various tire sizes and axle ratios based on what transmission you told it you have. http://www.grimmjeeper.com/gears.html
 
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Woodrow

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Critical rpms occur at redline. It's happy at any rpm you can stand and happy at rpms you can't stand if they're below redline. I ran mine for several years on the highway (before it was stolen) at 3100-3500 after converting my 5-speed manual with its 4.88 gearing to a 3-speed automatic which had no overdrive.

This gear ratio/rpm calculator is the only one I use, it has all the transmissions pre-stored into it so we can generate the exact rpms we'll get with various tire sizes and axle ratios based on what transmission you told it you have. http://www.grimmjeeper.com/gears.html

I don't think I asked my question well. I meant to ask about DRIVESHAFT RPM. I thought I recalled seeing a Tom Woods video in which they said you get driveshaft vibration commonly over a certain driveshaft RPM (like 3000?)
 

Blackjack

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Each jump in ratio gains you approximately 200 rpm at 60 mph if that help you any.
 

JMT

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I don't think I asked my question well. I meant to ask about DRIVESHAFT RPM. I thought I recalled seeing a Tom Woods video in which they said you get driveshaft vibration commonly over a certain driveshaft RPM (like 3000?)

Shawn did post an excessive driveshaft rpm. I think it was around 3000. This was in the discussion about harmonic vibes. I would like to find that thread again.
 
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97TJNM

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Personally, I LOVE my 4.88s. 4.0, 5 speed and 35's, and in mountainous terrain and high altitude. That said, stock gearing was 3.07s on my jeep, so it was a BIG jump for me. 70 in 5th on 4.88s is hovering right around 3k rpms, so I'm not sure I'd personally be happy with the even higher rpms of 5.13s.

That said, if you currently have 4.56 and want to go deeper, I doubt that 4.88 would give you enough extra to justify the cost. If I had 4.56 and was contemplating a regear, I'd probably just make the jump up to 5.13s.