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  • Question for Hemi Owners

    Hi Guys,

    I am trying to poll AEV HEMI JK Owners about their current gearing (4.10, 4.56, 4.88, etc..) and their experience with freeway driving. Please indicate which engine (6.4, 6.1 or 5.7) and transmission you have because it does make a difference (auto pre 2012, auto 2012+ or manual.)

    I am currently running an AEV JK450 setup with 37" BFG A/T tires (which are really closer to 35" at 33 PSI) with the GM 6.2L Ecotech Gen V and the 8L90e transmission. My jeep is geared at 4.88 and i am trying to see if i should go down to 3.73 or 4.10's. I know that most 2012+ 6.4 HEMI's built by AEV are geared at 4.56 but that's because the 5th gear of the WA580 transmission gear ratio is only 0.83. The 8L90e from GM has an 8th gear ratio of 0.65.

    Regardless, in 8th speed, I am at 65 MPH @ 2,000 RPM with 4.88 gears and it feels like the engine needs to drop to 1,500 RPM to be happy.
    Your thoughts ?




  • #2
    AEV FAN,

    I had a 6.4 Liter Hemi in a 2014 JKU with 4.10 gears on 35" tires. The setup worked fine but a 4.56 ratio would have been ideal up here in the altitude, 4800 FSL to 12,000 FSL. The 6.3 LS is a different beast where gearing is concerned. That engine makes it's torque at a lower RPM than the 6.4 L. I would say you are geared pretty well to maintain your throttle response. My engine didn't have a lot @ 2,000 RPM.

    I now have a F150 10 speed 10 r80 behind a 5.0 Liter V8. That trans goes from .80,.69,.63. At .63 the engine is just @ 1500 RPM with a 3.31 ratio, 32" stock tires. On the flat it gets awesome mileage but it will quickly downshift to 7th when acceleration is required. I really think 8 speeds is plenty in these vehicles as 10 seems over the top.

    My Jeep with 35" tires would not move sitting in the garage in neutral whereas the truck will roll right out of the garage. Those tires really eat up the power.

    I would leave your Jeep the way it is. I believe the LS conversion is ultimately the way to go and is pretty much plug & play nowadays.
    2012 JK 2 Door 2.5" AEV lift/ Fuel Hostage17 x 9 wheels, with Nitto 295x70 x 17 Tires. Warn Vr8000, Elite Bumper, LOD rear bumper, Teraflex tire carrier. Wife's Jeep!

    My Jeep. 2014 JKU, 6.4L Hemi AEV kit, 2.5" AEV lift, 35" Duratrac's. Gen Right aluminum bumpers, Warn VR 8000 winch. Pro Rock 44.

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    • #3
      Thread update: I ended up going back to 4.10's and believe it or not, it is still short geared for the LT. I am cruising close to 2,000 RPM at 80 MPH and the engine doesn't feel the need to downshift. If i had to do it again i would go to 3.73's with the 37's.

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