rpm with 4.10's
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I've got the 4.10's 4.0 and 32" KO's At 65 mph the engine is turning 2250 rpm depending on the accuracy of factory gauges. And yes, my speedo has been regeared to be pretty darn accurate.
I have a NV3550 trans and my first gear is pretty low...I can and often do start out in second gear if it's level or downhill. I had thought about 4.56 gears and 33's but ended up here and quite happy with my decision. I'm getting between 16-17 mpg overall and I wring it out a couple times a day since it is a new motor.
It's too bad that 4.30's are unavailable, because I know I'd gone with them.
I have a NV3550 trans and my first gear is pretty low...I can and often do start out in second gear if it's level or downhill. I had thought about 4.56 gears and 33's but ended up here and quite happy with my decision. I'm getting between 16-17 mpg overall and I wring it out a couple times a day since it is a new motor.
It's too bad that 4.30's are unavailable, because I know I'd gone with them.
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1,835 Posts
Ive got 33's and 4.10s, and the 5spd. first off I would really recommend the 4.56s like everyone above stated, there have been times driving in TN when I had to drop down into 3rd on the highway to keep it going lol, on flat ground its fine but any little hill will suck, as far as RPMS im right at 2000rpms doing 60
check out this gear ratio calculator its pretty nice- Gear Ratio Calculator
check out this gear ratio calculator its pretty nice- Gear Ratio Calculator
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Your numbers seem to be off, either you don't have 4.10 or your speedo isn't calibrated properly. I'm at 3k RPM with 4.88 and 33s at 75. The gear ratio calculator agrees with me. You should be at 2400 RPM at 75.
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75mph with 4.10s and 33''s would be 2473 rpms, with 4.56s it would be 2751 and with 4.88s it would be 2944, I suspect you have 4.88s as stated above
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2,389 Posts
eh I paid for 4.10's... I actually was thinking about this post tonight at work and I quoted the wrong numbers for myself. I am under 2500 at 75. I have to keep my speed under 2500 for gas mileage However I do know, I roll in 5th and do not require downshifting. I also know my speedo is correct, verified by GPS, and radar, and by time distance.
I am not running heavy mud tires or steel wheels though, but do have heavy bumpers and winch. I will drive today when I wake up and get an actual RPM for the thread.
I apologize for my state of confusion, I am on nights this week , and have not been sleeping to snuffy lol
I am not running heavy mud tires or steel wheels though, but do have heavy bumpers and winch. I will drive today when I wake up and get an actual RPM for the thread.
I apologize for my state of confusion, I am on nights this week , and have not been sleeping to snuffy lol
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As for downshifting to third I had to do it a few times on the highway in TN, but have yet to even have to drop to 4th here in VA, I will say me jeep probably weighs as much as a semi though loL! I have poison spyder rocker knockers, crusher corners (steel), steel fenders, winch with steel cable, steel gas tank / Xfer case / driveshaft skids, and steel bumpers lol
Oo, and steel rims (5) and like 50lbs of bedliner lol
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For the 4.0L engine, 5-speed transmission, and 33" tires, 4.56 is the optimal ratio for both highway and offroad use. 4.10 is not quite enough gear to restore the power lost by that larger diameter size tire. I made the mistake of regearing only to 4.10 for my then-33" tires years ago and it was a frustrating combination, I hated having to downshift for even minor grades... I regretted not having gone to 4.56 then as all my friends were recommending. I was wrong to have been afraid at the time of the 4.56's slightly higher RPMs.
Not to mention that the Jeep Rubicon came with 4.10 for its standard 31" tires... 4.10 is ideal for 31" tires, as evidenced by the factory choosing it for the Rubicon, but not 33".
Not to mention that the Jeep Rubicon came with 4.10 for its standard 31" tires... 4.10 is ideal for 31" tires, as evidenced by the factory choosing it for the Rubicon, but not 33".
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39 Posts
I've got 4.56s, run 32s and I turn 2250 at 60, 2500 at 65. I wish I'd gone with 4.10s, at least as highway running goes. But when I'm trail riding, i love those 4.56s!!
BTW I installed factory cruise on mine (that was a PITA!) and I can set my cruise at 60 and put it in 5th and pull some fairly big hills and the speed never wavers at all. But I've got 32s, not 33s. That might make a big difference, might by why some are suggesting 4.56s with 33s....
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yea. when I go to 35's I will regear to 4.88 just for grins and giggles. But where I am the 4.10 works real well for me.
I am not gonna regear to 4.56 to run 33's though, the 4.10's are barely 9 months old. I went to ECGS for the 8.8 axle swap, and regear, and Chase talked me into 4.10's since it was more of a daily driver he was of the mind set that 4.56 would be a bit too deep.
I am not gonna regear to 4.56 to run 33's though, the 4.10's are barely 9 months old. I went to ECGS for the 8.8 axle swap, and regear, and Chase talked me into 4.10's since it was more of a daily driver he was of the mind set that 4.56 would be a bit too deep.
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