Manual transmission gearing

[Obscurity]

I'm fairly new to jeeps so please forgive me if this has been talked to death. I've had my jlur for several weeks driving it around atlanta with no issues. This weekend we drove to the NC mountains and I am noticing a huge gap between some off the gears. Driving up a curvy steep incline I found I can easily do it in 2nd but not very fast. If I want to pick up the place and shift to third there is almost no power of I shift at 3000 rpm because the revs drop to aound 2200. Third doesn't have any real power until you get north of 2600 rpms but to do that you have to get 2nd to 3600 rpm and you are driving to fast for the curvy road. 2nd and 3rd are just too far apart. Meanwhile 5th and 6th are practically the same gear.

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[azwjowner]

2nd and 3rd are just too far apart. Meanwhile 5th and 6th are practically the same gear.

You are 100% correct. But there's nothing any of us can do about it. The best alternative is to aggressively regear, which doesn't change the relative gear ratios, but moves the gears closer together in terms of vehicle speed. I'm running 4.56 on 32" tires, so my 2nd and 3rd are a bit closer together now in terms of speed and how soon I shift.

 

[grimmjeeper]

Don't be afraid to rev the V6. It likes higher RPMs. It can carry on well above 5,000 RPM. It's the opposite of a diesel.

Keep it up in the power band and don't shift up too soon. Especially when climbing hills. You absolutely want to go over 4,000 or so before you shift up so you're still making decent power for the next gear.

 

[toothirtyj]

The 3.6L engine can be wound out, and live, near the top of the RPM range where the power is.

Don't be afraid to keep the RPM's up. You won't hurt the motor.

@grimmjeeper beat me by a nose

 

[Obscurity]

You are 100% correct. But there's nothing any of us can do about it. The best alternative is to aggressively regear, which doesn't change the relative gear ratios, but moves the gears closer together in terms of vehicle speed. I'm running 4.56 on 32" tires, so my 2nd and 3rd are a bit closer together now in terms of speed and how soon I shift.

I assume this negatively affects mileage?

 

[toothirtyj]

I assume this negatively affects mileage?

Not necessarily. It depends on how you drive your Jeep.

Having a JLUR you already have 4.10 gearing so if you plan on keeping stock tires, changing your gear ratios isn't really an appropriate solution to your problem.

Put the 3.6L through it's paces and use the whole RPM range. You might be pleasantly surprised with the results.

 

[azwjowner]

I assume this negatively affects mileage?

Maybe a bit. Depends what your RPM is at your cruising speed. I'm in 6th at 2500 RPM @ 70 MPH, which is as fast as I go. Probably a little mileage loss there versus if the engine was at 2200 RPM or such, but faster revs are at least somewhat offset by having less load on the engine.

 

[azwjowner]

Having a JLUR you already have 4.10 gearing so if you plan on keeping stock tires, changing your gear ratios isn't really an appropriate solution to your problem.

I disagree here, as 4.56 with 32s is perfect. On 33s with a Rubicon I'd regear to 4.88. Yes, it's a lot of gear -- too much for some -- but it totally transformed the manual.

 

[YJdude]

I'm fairly new to jeeps so please forgive me if this has been talked to death. I've had my jlur for several weeks driving it around atlanta with no issues. This weekend we drove to the NC mountains and I am noticing a huge gap between some off the gears. Driving up a curvy steep incline I found I can easily do it in 2nd but not very fast. If I want to pick up the place and shift to third there is almost no power of I shift at 3000 rpm because the revs drop to aound 2200. Third doesn't have any real power until you get north of 2600 rpms but to do that you have to get 2nd to 3600 rpm and you are driving to fast for the curvy road. 2nd and 3rd are just too far apart. Meanwhile 5th and 6th are practically the same gear.

The 3.6 is gutless below 2500 RPM. It was quite a shock to me when I got mine after being used to the 4.0L being able to do pretty much anything below 2500. Like others have said, it's happy at high revs. You will also see better mileage with it wound out than you would lugging it at 2000.

 

[azwjowner]

The 3.6 is gutless below 2500 RPM. It was quite a shock to me when I got mine after being used to the 4.0L being able to do pretty much anything below 2500. Like others have said, it's happy at high revs. You will also see better mileage with it wound out than you would lugging it at 2000.

That's the truth. I had the 4.0 in my WJ and it was rare that I'd ever be over 2500 RPM. The 3.6 is the exact opposite.

 

[toothirtyj]

I disagree here, as 4.56 with 32s is perfect. On 33s with a Rubicon I'd regear to 4.88. Yes, it's a lot of gear -- too much for some -- but it totally transformed the manual.

@Obscurity ... You can spend thousands of dollars for new gears and proverbially kick the can up the gear range or, again, simply use your engine's full potential. Hope this helps.

 

[Obscurity]

Don't be afraid to rev the V6. It likes higher RPMs. It can carry on well above 5,000 RPM. It's the opposite of a diesel.

Keep it up in the power band and don't shift up too soon. Especially when climbing hills. You absolutely want to go over 4,000 or so before you shift up so you're still making decent power for the next gear.

This is so counter to my 4 cylinder experience. I always tried to keep it under 3000 and this usually worked in all situations

 

[Ol’ Timey Manual SWB Guy]

Probably worth mentioning (especially to any casual readers of this thread) that the word “regear” in the context of the OP’s manual transmission question doesn’t actually mean doing anything to the gears within the manual transmission. It means changing the pinion gear and the pinion ring in the differentials (front and rear axle alike) to a ratio that drops ALL the manual transmission’s gears into more useful ranges, without actually touching the transmission’s gears, per se. We use the word “regear” casually here, but it’s a bit of a misnomer. It probably should’ve been “repinion” or something. But “regear” rolls off the tongue better.

In my case (2dr JL), I can’t imagine the point of my factory sixth gear, given my factory 3.45 Overall Top Gear Ratio. I’d practically have to be falling from an airplane to get out of fifth. Indeed, IMHO, a 2dr shouldn’t be hustling along at the peak highway speeds that factory sixth might theoretically allow. I rarely get out of factory fourth.

 

[azwjowner]

@Obscurity ... You can spend thousands of dollars for new gears and proverbially kick the can up the gear range or, again, simply use your engine's full potential. Hope this helps.

I don't disagree, but just to explain what I mean. These charts are particular for my Jeep on 32s. The first one is the 3.45 stock gears. The second one is with 4.56. Look at the 3000 RPM column. I had a gap of 22 mph between 3000 RPM in 2nd and 3rd. That shrunk to 17 mph. Similar for all the other gears.

Gear	750 RPM	3000 RPM	6000 RPM
Road speed at given RPM in miles per hour
1	4	16	31
2	8	31	61
3	13	53	105
4	20	80	161
5	25	99	199
6	28	112	223

Gear	750 RPM	3000 RPM	6000 RPM
Road speed at given RPM in miles per hour
1	3	12	24
2	6	23	46
3	10	40	80
4	15	61	122
5	19	75	150
6	21	85	169

 

[Az-jewel]

I agree with those who said to push the rpms. It's hard to do that mentally but the engine has no oomph without it!!

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