Honest Feedback Requested 6 Speed Manul

[Kluk Ztopolovky]

Next mayor better get rid of the bike lanes

yes, I would make cycling on busy motorways illegal and those unwilling to comply I would move to Cuba , Vietnam or China

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[iklln6]

What kinda gas mileage are you seeing with the daytime driving in 4th gear? 80% of my commute is 40 miles per hour, 43 miles one way. Thanks.

I haven't measured, and I'm not going to open the can of worms with this community by estimating. What I will say is I make regular drives between OKC and Houston and have a set routine of when I refuel based on tank level (I'd generally start looking for a convenient exit with the needle at 1/4) which put me at the same handful of gas stations on the route...After adopting the aforementioned style, I'm still stopping at the same stations. That route I'm going between 70 and 80 mph most of the drive and ... believe it or not ... the jeep does not have the most aerodynamically efficient shape (Raytheon is NOT redesigning the AIM-9 Sidewinder based on the contours of the JL)... My suspicion is that paired with the Rubi gearing and tires means the throttle stays more open in 6th gear than in 4th to overcome the force of drag by just enough to nearly compensate for the advantage of the reduced RPM.

For a 40mph commute...when aerodynamics are less of a concern...go back to conventional wisdom.

I realize and accept the can of worms I am opening by answering this

 

[DanW]

I'd bet at 40 in 4th gear you'd get outstanding mileage, if there aren't many stoplights. My commute is that way, but with many stops. I easily get 19 and 20 with the ESS. No doubt it would be significantly better with fewer stops. I mostly don't use the ESS, though. I can't help but think it puts more wear and tear on the starter.

 

[Ronnie S]

I'd bet at 40 in 4th gear you'd get outstanding mileage, if there aren't many stoplights. My commute is that way, but with many stops. I easily get 19 and 20 with the ESS. No doubt it would be significantly better with fewer stops. I mostly don't use the ESS, though. I can't help but think it puts more wear and tear on the starter.

I’m at 19.5mpg and I do stop and go traffic on the dreaded I-96 east every morning. When there’s no stop and go traffic (Friday’s) and I can just do 70-75 it still gets in the 19-20 range. These 3.6’s seems very efficient in all conditions. I don’t use the ESS either. Starting the engine is always the hardest thing for engine wear. Why would I want to keep doing it while driving. Lol!

 

[johnnymiz]

The odd thing is, youre only looking at a 300 rpm difference at 70mph between 5th and 6th. Idk why they chose such close overdrive ratios....shoulda made a 5 speed and left it at that.
It isnt like the extra gear is going to come in handy...who ever says, "i really like the look of those skinny little prius tires, im gonna put a set on my rubicon!". Uh, no one.
I had a 69 camaro with a warmed up 96 LT1 and T-56 6 speed in it.... that had .25 between 5th and 6th compared to the D478 .09 between overdrives.
I guess it had to do with the lack of low end torque of this motor. I can really see how 6th will cause you to actually keep more throttle depending on aerodynamic variables....especially at 80mph.
Compared to the 3.6 roughly 100lb/ft at 2000rpm, my camaro had over 300lb/ft at that speed in a much more aerodynaic package. That thing would cruise at 70 with the motor loafing along at 1700 rpm....gving me far better gas mileage than i deserved (22mpg) on long rides. But it was the massive torque at that rpm that made it possible. All issues here seem to me to be the fault of the 3.6 and not the transmission.

 

[DanW]

The odd thing is, youre only looking at a 300 rpm difference at 70mph between 5th and 6th. Idk why they chose such close overdrive ratios....shoulda made a 5 speed and left it at that.
It isnt like the extra gear is going to come in handy...who ever says, "i really like the look of those skinny little prius tires, im gonna put a set on my rubicon!". Uh, no one.
I had a 69 camaro with a warmed up 96 LT1 and T-56 6 speed in it.... that had .25 between 5th and 6th compared to the D478 .09 between overdrives.
I guess it had to do with the lack of low end torque of this motor. I can really see how 6th will cause you to actually keep more throttle depending on aerodynamic variables....especially at 80mph.
Compared to the 3.6 roughly 100lb/ft at 2000rpm, my camaro had over 300lb/ft at that speed in a much more aerodynaic package. That thing would cruise at 70 with the motor loafing along at 1700 rpm....gving me far better gas mileage than i deserved (22mpg) on long rides. But it was the massive torque at that rpm that made it possible. All issues here seem to me to be the fault of the 3.6 and not the transmission.

I agree that 300 rpm is hardly with it, but here magical high tech feature... It CAN transform itself right before your eyes into a 5 speed. Just don't shift into 6th!

I will add that with 35s, I just matched your Camaro doing 70mph and 22mpg. It has nowhere near the pull of that Camaro at that speed, but it also, as you said, lacks the aero and also has a heavier duty 4wd drive train siphoning off power . As for comparing engines, the Chevy has DI which I'd rather live without. It is also pushing around a lighter sports car. I've driven V6 Camaros and Challengers back to back and the Pentastar puts out about 300 hp in that application and was very competitive with the Camaro.

So why would I rather have 285 hp without DI than 300 with it? Long term durability and reliability. GM revised Dexos because DI causes particulates that were degrading the polymer timing chain guides and causing timing chain wear. I believe they have solved it, but that effort was never required for the Pentastar because there was no issue there to begin with. There have also been issues with carbon buildup in valves over time. Again, not an issue with the Pentastar. If a Pentastar does get that, simply running higher quality fuel cures it.

Don't get me wrong, I love GMs 3.6. I owned one in a Buick Enclave. But, the Pentastar compares very well to it without resorting to DI.

 

[johnnymiz]

Hahaha
So true
Some guys have magically made it a 4 speed the same way.
I DO catch 6th, a lot, but i am very mindful to be judicious with the skinny pedal...very light touch or you waste the benefit of the higher gear.
And i like the D478 ...i think it is a great tranny....old school stump puller first with a nice overdrive.
Really couldve used that in my FJ40 or 68 Scout. I wish the 3.6 just had more grunt below 2k rpms like the FJ and IH.

 

[Rogues Gambit]

yes, I would make cycling on busy motorways illegal and those unwilling to comply I would move to Cuba , Vietnam or China

I was just in NYC yesterday and I saw guys blowing past reds, riding in the wrong lane, riding in the middle of the street and speeding up with the cars... Don't need to be a genius to see why there's been an increase in deaths

 

[Skuj]

We like ours. Only thing annoying is when slowing down for a stop light if you’re going very fast at all and try to get it in first in preparation for the green it might try and grind a bit. Come to nearly a stop and it goes in fine.

When we ordered my wife’s she wanted an auto

Brett

I experience the exact same behavior which required some getting used to. I slow it down to get it below 5 MPH and it shifts better into 1st.

 

[melman8r]

I'd bet at 40 in 4th gear you'd get outstanding mileage, if there aren't many stoplights. My commute is that way, but with many stops. I easily get 19 and 20 with the ESS. No doubt it would be significantly better with fewer stops. I mostly don't use the ESS, though. I can't help but think it puts more wear and tear on the starter.

Thanks for the honest feedback...

 

[melman8r]

I haven't measured, and I'm not going to open the can of worms with this community by estimating. What I will say is I make regular drives between OKC and Houston and have a set routine of when I refuel based on tank level (I'd generally start looking for a convenient exit with the needle at 1/4) which put me at the same handful of gas stations on the route...After adopting the aforementioned style, I'm still stopping at the same stations. That route I'm going between 70 and 80 mph most of the drive and ... believe it or not ... the jeep does not have the most aerodynamically efficient shape (Raytheon is NOT redesigning the AIM-9 Sidewinder based on the contours of the JL)... My suspicion is that paired with the Rubi gearing and tires means the throttle stays more open in 6th gear than in 4th to overcome the force of drag by just enough to nearly compensate for the advantage of the reduced RPM.

For a 40mph commute...when aerodynamics are less of a concern...go back to conventional wisdom.

I realize and accept the can of worms I am opening by answering this

Makes sense, thanks...

 

[iklln6]

Did you a solid. I looked up the gear ratios and calculated the travel speeds in each gear based on RPM, then reality-checked the numbers with a test drive. Here goes:

The 2018+ 6-Speed Transmission is an Aisin AL6 [1] D478 [2] with gear ratios [3]:
1st - 5.13
2nd - 2.63
3rd - 1.53
4th - 1.00
5th - 0.81
6th - 0.72
Reverse - 4.49

I have the Rubicon (should have specified earlier) so I have the 4.10 final gearing, and my stock tires are 285/70R17

Reduction Ratio:
Transmission Gear Ratio x Axle Gear Ratio

Tire: 285/70R17
285 x (12" / 300mm) x 0.70 = Tire Height (distance from rim to tread)
17" Wheel diameter
2x Tire Height + 17" = Total Tire Diameter (32.96", but for reality's-sake I am assuming 32" due to wear and some stretch)
Total Tire Diameter x PI = Total Tire Circumference (inches)
Total Tire Circumference x ( 1 ft / 12 in ) x ( 1 mi / 5280 ft ) = Total Tire Circumference (miles)
RPM x 60 = rotations per hour

Engine RPM x 60 = Engine RPH
Engine RPH / (Transmission Gear x Final Gear) = Wheel RPH
Wheel RPH x Total Tire Circumference (miles) = Travel Speed (mph)


Engine RPM 1st (mph) 2nd (mph) 3rd (mph) 4th (mph) 5th (mph) 6th (mph)
750 3.4 6.6 11.4 17.4 21.5 24.2
1000 4.5 8.8 15.2 23.2 28.6 32.2
1250 5.7 11.0 19.0 29.0 35.8 40.3
1500 6.8 13.2 22.7 34.8 43.0 48.3
1750 7.9 15.4 26.5 40.6 50.1 56.4
2000 9.0 17.6 30.3 46.4 57.3 64.4
2250 10.2 19.8 34.1 52.2 64.4 72.5
2500 11.3 22.1 37.9 58.0 71.6 80.6
2750 12.4 24.3 41.7 63.8 78.8 88.6
3000 13.6 26.5 45.5 69.6 85.9 96.7
3250 14.7 28.7 49.3 75.4 93.1
3500 15.8 30.9 53.1 81.2
3750 17.0 33.1 56.9 87.0
4000 18.1 35.3 60.6 92.8
4250 19.2 37.5 64.4 98.6
4500 20.3 39.7 68.2
4750 21.5 41.9 72.0
5000 22.6 44.1 75.8
5250 23.7 46.3 79.6
5500 24.9 48.5 83.4
5750 26.0 50.7 87.2
6000 27.1 52.9 91.0

I thought it silly to include speeds over 100 mph...but from the above table you can get an idea for what kind of RPM you're at at various speeds. 75 mph in 6th is between 2250 RPM and 2500; 75 mph in 5th is between 2500 and 2750; 75 mph in 4th is about 3250 rpm. The force of drag acting on the jeep flying down the highway is a function of the velocity squared [4]--that force being imparted on the vehicle must be overcome just as though you were slowly driving up a hill (drag equal to half the curb weight of the vehicle would be like driving up a 30 degree incline). At what grade hill would it be better to downshift? Idk but here you go, the tools of curiosity.


[1]: https://en.wikipedia.org/wiki/Jeep_Wrangler_(JL)
[2]: https://en.wikipedia.org/wiki/List_of_Aisin_transmissions
[3]: (Google "D478 Gear ratios" -- it's from jlwranglerforums but the link is long)
[4]: https://en.wikipedia.org/wiki/Drag_equation

 

[CoryC]

All in all the transmission shifts well and the clutch is smooth. It works great in 4low, but has a propensity to stall in 4hi, especially in reverse. I’ll admit, I’m accustomed to the low end torque in my CJ, so I’m not used to babying the JL.

I occasionally experience the bucking and surging as well. It always occurs in first gear at low speed - usually on a slight incline, like my driveway unfortunately. I learned to drive in a standard transmission and all my cars since have had a stick, so I’m sure I’ve picked up a few bad habits. Perhaps @OldGuyNewJeep can enlighten me (and others) on how to prevent the bucking and surging. As mentioned by others in this post, it is very annoying - especially when the neighbors are watching! ;-)

I've also only driven manuals in my 20+ years driving... and this is vehicle #20 (yes, yes... I know...) but this transmission is fantastic! I had a Hummer H3 manual as well as a 2014 Tacoma TRD, and while they both were among the better "truck" manual transmissions I've experienced, this one is the best. The cable connection eliminates the shifter vibration and wobble completely and each shift it really crisp. No... it doesn't like to be quickly run through the gears like a sportscar... but it's NOT a sports car, though the shifter feels that good. As to the first gear surges and bucking... this engine idles low and has very little torque down there... it needs a bit of engine speed to get you going. I find I have the same issue, especially with the radio on since the engine is so quiet and I can't hear where I want the revs to be when I engage first gear. It's like switching to any other new manual, you'll develop the muscle memory for the engagement point in the pedal, and begin to find the right amount of throttle in different situations to minimize that. The pedal is so soft it takes some finesse to really hold it a little longer at the sweet spot letting the drivetrain catch up to the engine and allow for smooth engagement... but I'm getting there. First and reverse are two very different animals due to the gear differences too... so what works for one is a little different for the other! I wish I had a quick fix for you, but just drive it more and more and you'll settle in to exactly how it likes to be engaged... that just means more driving fun!

 

[johnnymiz]

@iklln6, that post was awesome. It should be stickied somewhere in the tech section

 

[m3reno]

I was just in NYC yesterday and I saw guys blowing past reds, riding in the wrong lane, riding in the middle of the street and speeding up with the cars... Don't need to be a genius to see why there's been an increase in deaths

Problem is nobody stops to look anymore, they just figure they have the right away. Yesterday some lady on a bike just went right through the cross street without even looking as a cement truck , who had the right away, was coming for a delivery. This is all DiBlasio's fault, He's a complete moron!!

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