6sp MT Rubicon gearing

[Gatorized]

I'm surprised to hear that someone is actually OK with the stock 1st gear. I, too, am on 35s and find it to be awful.

I was pulling off the highway the other day to go hunting, and had to pull up to park on top of an embankment. Not super steep. I had it in first and it legitimately tried to stall out on the way up, in 1st! Kind of like you would expect if you were in too high of a gear and floored it, yet it doesn't really go anywhere. It was that, but I was in 1st/2WD.

I've never had an issue with stalling on mine. But I know others have, so it's legit. I don't know why, but I don't have an issue taking off in first. I don't care for reverse (too long), and third is too long since I could max out the speed governor in 3rd. But 1st and 2nd are honestly fine for me.

I’ve found that the linkage is just clunky enough if not paying close attention you can wind up in 3rd when you are going for 1st in a hurry… so you very well may have been in too high a gear to crest the slope.

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[AustinL911]

I’ve found that the linkage is just clunky enough if not paying close attention you can wind up in 3rd when you are going for 1st in a hurry… so you very well may have been in too high a gear to crest the slope.

Nope. Was in 1st going about 5mph as I had just crawled over a ditch. Just not high enough into the RPMs to be in the power and it's not geared low enough to climb the embankment. Had I been around 2k RPMs, I'm sure it would be fine. But it certainly couldn't do it without slipping the clutch at that low speed/load.

 

[Rahkmalla]

NP-435 Gear Ratios: (1,2,3,4,R): 6.69, 3.34, 1.79, 1.00,8.00

I understand cafe regs and all but the NP-435 is geared how a truck should be geared. I would gladly take the 1 -4 gears of the NP-435 in the jeep with the 5th and 6th for highway.

What's the final drive of your 75? I was under the impression older jeeps had much taller diff ratios which could by why the transmission itself was much shorter.

 

[ericnewcom]

What's the final drive of your 75? I was under the impression older jeeps had much taller diff ratios which could by why the transmission itself was much shorter.

My 75 F250 “Hi-Boy” has 4.10 front and rear. Hopefully myJTR MT will be more like It after a re gear. I’m thinking 4.88 but might do 5.18 I think is what I’ve seen mentioned.

 

[bd100]

I should mention that my engine complained and lugged a lot until 500 miles break in then it suddenly was much happier at low RPM.

 

[ericnewcom]

I should mention that my engine complained and lugged a lot until 500 miles break in then it suddenly was much happier at low RPM.

That’s good information thanks for sharing.

 

[lppd45]

What bd100 said. Mine really didn't "break in" until after 1 - 2k.

 

[Bbannongmu]

Checkout the 4.88 v 5.13 video that @Jt-wrx and I put together. Re gearing is deftly worth it. depends on how you use your JT and where you live. After going to Yellowstone this summer I wished I had 5.38 gears on some of those mountains! Hit me up with any questions. Good luck!

 

[ericnewcom]

Checkout the 4.88 v 5.13 video that @Jt-wrx and I put together. Re gearing is deftly worth it. depends on how you use your JT and where you live. After going to Yellowstone this summer I wished I had 5.38 gears on some of those mountains! Hit me up with any questions. Good luck!

Really good comparison between the two. Thanks for posting. Off topic a little but what size lift are you running to run your 37s? Can you still fit in a 7' tall door? I was looking today (haven't measured yet) and there is quite a bit of room from the top of my gladiator on stock 33s and the door but my f250 Tremor on 35s only has 2 inchs of space between the roof and the door. I'm pretty sure a 2" lift and 37s on the Rubicon gladiator would still fit. I know for sure 35s on factory Rubicon ride height would have more space than the Tremor.

 

[Jt-wrx]

Really good comparison between the two. Thanks for posting. Off topic a little but what size lift are you running to run your 37s? Can you still fit in a 7' tall door? I was looking today (haven't measured yet) and there is quite a bit of room from the top of my gladiator on stock 33s and the door but my f250 Tremor on 35s only has 2 inchs of space between the roof and the door. I'm pretty sure a 2" lift and 37s on the Rubicon gladiator would still fit. I know for sure 35s on factory Rubicon ride height would have more space than the Tremor.

I’m on 37’s with mopar 2” lift plus 3/4” pucks up front and clear into my 7’ garage ok. You may be able to get in with a 4” lift but don’t think 6” would work.

 

[ericnewcom]

I’m on 37’s with mopar 2” lift plus 3/4” pucks up front and clear into my 7’ garage ok. You may be able to get in with a 4” lift but don’t think 6” would work.

Really appreciate the info. My current plan is to regear to 4.88 and switch to 35s when the 33s wear out on the stock suspension. I’ll most likely end up with 2” lift and 37s. It’s my first Jeep. I kinda want to enjoy the ride / journey and not go full tilt out of the gate. I’m not new to off roading or modding but new to the Jeep world.

 

[Bbannongmu]

Really good comparison between the two. Thanks for posting. Off topic a little but what size lift are you running to run your 37s? Can you still fit in a 7' tall door? I was looking today (haven't measured yet) and there is quite a bit of room from the top of my gladiator on stock 33s and the door but my f250 Tremor on 35s only has 2 inchs of space between the roof and the door. I'm pretty sure a 2" lift and 37s on the Rubicon gladiator would still fit. I know for sure 35s on factory Rubicon ride height would have more space than the Tremor.

I’m running a Rusty’s 2” “plus” lift with a Teraflex 1.5” leveling kit up front and a Daystar .75” puck in the back. The Mickey Thompson AtzP3’s are over 36.3” tall under load with 30psi. I can clear a 7’ door ok.

 

[Bbannongmu]

It was built correctly as designed. The gears are what the government mandates they must be. Three lower forwards gears, a direct drive, and two overdrives for a minor improvement in fuel efficiency at speed. I guess the JK had four forward, a direct, and one overdrive, which I would have preferred. There is no creeper first and no creeper reverse. The lack of a creeping reverse really hurts, and could be due to packaging limitations or the like.

I have a JT with 3.73 diffs. It's even worse than your 4.10s. I get to use 6th at 70MPH or so if not towing, and reversing up the driveway is bursts of feathering the clutch all the way.

A Centerforce clutch can help with the tendency to stall, and for offroading.

1st: 5.13
2nd: 2.63
3rd: 1.53
4th: 1.00
5th: 0.81
6th: 0.72
Reverse: 4.49

Centerforce clutch and proper axle gears make a huge difference!!

 

[hjdca]

Centerforce clutch and proper axle gears make a huge difference!!

Agreed. I'm running 3.5" lift, 37s, Dana Spicer 5:13s, winch, armor, & medium weight in the bed, with a JTR manual shift and it seems just perfect where I live - So Cal Mountains.

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