Engine and manual transmission break in

[bd100]

3.6L and 6-speed manual transmission. A lot of people do a test drive and complain about the lack of low-end torque and the touchy clutch. My truck was the same at first.

We also have a Pentastar with the automatic 8 speed, and it happily putters around at 1200 RPM around town under computer control, so I knew the new manual trans JT would probably be fine after a while. Sure enough:

The clutch does get much easier after it is broken in, but it's interesting that after around 200 miles the engine was much happier at low RPM than when it was new, and after 500 it was better still. At this point it's just as fine at low RPM as my old v8 pickup. By that I mean it doesn't grumble like it did when new, but it's still a v6 so it will never be as smooth at low RPM compared to the 8. But it's driveable. You can do 3rd out of a fast turn just as much as the v8 does. The shift points are about the same. And you can cruise around town at 1200, 1300, 1400 RPM. You can use 5th at 40mph with 3.73 diff gears. 6th at 60. And the clutch is much more normal now.

So if you based your impression of the manual transmission and 3.6 on a test drive of a new vehicle, know that it gets much better after a bit.

And for anyone with a new automatic, it'd be interesting to know if the computer avoids cruising at 1200-1300 RPM for the first few hundred miles.

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[Hootbro]

And for anyone with a new automatic, it'd be interesting to know if the computer avoids cruising at 1200-1300 RPM for the first few hundred miles.

MY 2021 Willys with the 8 speed avoided 8th gear for the most part until around 5K miles and finally settled in. Was more prevalent the colder the temps outside were.

Now at 10K miles and am happy with the transmission performance. While I never really paid attention to shifting so much on my 2020 Rubicon JT, it seems to be a better shifting transmission out the gate than my 2021 Willys JT.

 

[NachoRuby]

I like the manual a lot, but you must be somewhere much flatter than here. I can't cruise at 1200-1400 rpm, or I'll bog down with every slight incline. Which is to say everywhere. It's all rolling hills here. The sweet spot is 2000 RPM plus for me, in my area, unless it's really flat, which it rarely is around here. I don't mind it though. Same deal on the 3.6 in our 2016 JKU, with the older transmission/engine combo.

I'm at almost 22,000 miles. Still love it, but I can't cruise that low.

 

[Sammar]

I like the manual a lot, but you must be somewhere much flatter than here. I can't cruise at 1200-1400 rpm, or I'll bog down with every slight incline. Which is to say everywhere. It's all rolling hills here. The sweet spot is 2000 RPM plus for me, in my area, unless it's really flat, which it rarely is around here. I don't mind it though. Same deal on the 3.6 in our 2016 JKU, with the older transmission/engine combo.

I'm at almost 22,000 miles. Still love it, but I can't cruise that low.

2000 rpm is spot on for me too
I live in hilly Pittsburgh.

It took about 5000 miles for everything in the transmission to really settle in. Been driving a manual for the past 20 years and was surprised how long it took for me to settle in with the transmission, but all is well now. I love it

 

[BA33]

It took about 5000 miles for everything in the transmission to really settle in. Been driving a manual for the past 20 years and was surprised how long it took for me to settle in with the transmission, but all is well now. I love it

This is the same experience I had with my JL, although I wasn't really paying attention to when the transmission sorted itself out. I just kind of had an epiphany one day, like "Wow! The transmission is so much better now!" Found that 16-1700 rpms was best for mileage and around 2000 rpm was where the engine was much more responsive.

 

[bd100]

Sorry, 1200 RPM was referring to puttering down a flat suburban road at mild speeds, for example. And that's about as low as it's happy. Like everyone else, it's more like 1500-2000 most of the time around town, 2000ish on the highway. But when new it would really grumble down low, thus many of the complaints about no low end torque. But it got better.

 

[Afternoon Spray]

3.6L and 6-speed manual transmission. A lot of people do a test drive and complain about the lack of low-end torque and the touchy clutch. My truck was the same at first.

We also have a Pentastar with the automatic 8 speed, and it happily putters around at 1200 RPM around town under computer control, so I knew the new manual trans JT would probably be fine after a while. Sure enough:

The clutch does get much easier after it is broken in, but it's interesting that after around 200 miles the engine was much happier at low RPM than when it was new, and after 500 it was better still. At this point it's just as fine at low RPM as my old v8 pickup. By that I mean it doesn't grumble like it did when new, but it's still a v6 so it will never be as smooth at low RPM compared to the 8. But it's driveable. You can do 3rd out of a fast turn just as much as the v8 does. The shift points are about the same. And you can cruise around town at 1200, 1300, 1400 RPM. You can use 5th at 40mph with 3.73 diff gears. 6th at 60. And the clutch is much more normal now.

So if you based your impression of the manual transmission and 3.6 on a test drive of a new vehicle, know that it gets much better after a bit.

And for anyone with a new automatic, it'd be interesting to know if the computer avoids cruising at 1200-1300 RPM for the first few hundred miles.

I know this is an old thread but this has not been my experience. I'm 7,000 miles into a 2024 Manual Transmission Rubicon with the 4.10 gearing and as much as I love my truck, 6th gear is unusable. Today in 6th gear it couldn't maintain 75MPH on a flat stretch of highway. I can't maintain 70MPH in 5th gear with even 1 degree of uphill grade. My truck struggles to accelerate at anything under 2200 RPM. It's effecitvely a 4 speed Manual because in the PNW there are so few perfectly flat roads that would ever allow me to coast in 5th gear.

 

[Thunderspud]

I know this is an old thread but this has not been my experience. I'm 7,000 miles into a 2024 Manual Transmission Rubicon with the 4.10 gearing and as much as I love my truck, 6th gear is unusable. Today in 6th gear it couldn't maintain 75MPH on a flat stretch of highway. I can't maintain 70MPH in 5th gear with even 1 degree of uphill grade. My truck struggles to accelerate at anything under 2200 RPM. It's effecitvely a 4 speed Manual because in the PNW there are so few perfectly flat roads that would ever allow me to coast in 5th gear.

Without getting into the weeds on tire sizes, driving habits, geography, etc........it's worth mentioning that our manuals ARE essentially a 4 speed.......with two overdrive gears.

 

[bd100]

I'm 7,000 miles into a 2024 Manual Transmission Rubicon with the 4.10 gearing and as much as I love my truck, 6th gear is unusable.

Keep going! Maybe break it in a bit more with full throttle 3000 to 4000 RPM bursts.

Tire size?

 

[Afternoon Spray]

Keep going! Maybe break it in a bit more with full throttle 3000 to 4000 RPM bursts.

Tire size?

Stock Rubicon tires. 285/75/17. The stock falken wild peak MTs are HEAVY. I want to swap them out for some lighter ATs but can't justify the price when I have a ton of wear left.

 

[bd100]

I wouldn't give up yet. Did you do a break-in procedure yet? Full power bursts at mid RPM.

 

[Afternoon Spray]

Not planning to give up on it. Bought this to be my last car, especially now that they discontinued the manual. Only future I envision I get rid of it would be to give it to my daughter when she turns 16.

I thought I followed the break in procedure prescribed in the manual. I'll try to give it some more full throttle bursts in the 4k RPM range if you think that'll help.

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