JL 3.6 Manual Transmission Clutch.... Please ELI5

[Rodeoflyer]

Congrats on passing on the skill to the next generation! Drivers ED cars should still be manual.

This monstrosity exists because of CAFE fuel economy standards. In order to squeak out a higher number, manufacturers went to auto start-stop systems. It takes fuel to start and engine, but the lower your rotational mass, the less fuel it requires, plus, it's easier on the starter motor for additional reliability. To lower the rotational mass, they reduced the size and weight of the flywheel.

That had the negative affect of reducing the torque capability of the clutch assembly, so they went with a twin-disc design to double the area of friction surfaces to regain that clamp load. On the flywheel side, the low-mass flywheel was insufficient to absorb the nvh of the motor so the dual-mass design effectively canceled unwanted vibration at a lower overall mass.

All of this is terrific for a small car or SUV. It's terrible for a heavy SUV, especially one that's going to see larger heavier tires. Plus, once we install our Tazers and deactivate the auto-start-stop, the benefit of this clutch system is completely neutralized.

The CF is a basic design that's worked well since the beginning of motorized times. There weren't any reliability issues with the clutches themselves, it was the stock hydraulics that were out-matched. That has been improved upon. I don't know about an install video but there are a few step-by-step threads on this forum covering it.

Absolutely.. a manual transmission saves wear on EVERY other part of the drivetrain. There is no doubt about that. It saves your brakes, it saves your motor, saves your gears and lockers, it doesn't need a torque converter, it's the THE simplest of drivetrain connectivity known to man. I rarely even have to use my brakes.. IF you know how to use a proper manual trans.

CAFE and profit over reliability is the devil IMO

And brake dust, the environmental impact is greatly reduced with a manual trans.

It's about PROFIT not environmental issue

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[Toycrusher]

Absolutely.. a manual transmission saves wear on EVERY other part of the drivetrain. There is no doubt about that. It saves your brakes, it saves your motor, saves your gears and lockers, it doesn't need a torque converter, it's the THE simplest of drivetrain connectivity known to man. I rarely even have to use my brakes.. IF you know how to use a proper manual trans.

CAFE and profit over reliability is the devil IMO

And brake dust, the environmental impact is greatly reduced with a manual trans.

It's about PROFIT not environmental issue

To be fair, brakes and clutches are often made of the same materials. But you are correct, on their own, all the energy stored in a moving vehicle needs to be converted to heat by the brake pads. If you slow with your engine, some of the energy is converted to heat by the clutch, but the rest of the energy is converted to heat by engine friction and sent out through the cooling system. Measurably "cleaner" than brakes alone.

 

[Rodeoflyer]

Yep and I forgot about the transfer case as well IF you have the 4hi type clutch it it. But those guys all have autos haha

 

[DP79]

A complete transmission swap is what's otherwise known as "opening a can of worms". It's challenging when you have a complete donor vehicle to steal from. If such a vehicle has never existed, it's even more so fun.

I manual swapped my 360ci Ram pickup. Plenty of 5.2 manual Rams but the 5.9/manual combo was never offered in the 2nd+ gen truck. Most things were adaptable from the 5.2 trucks, but I'm currently pending a custom ECM as the 5.9 ECM doesn't know how to handle certain conditions with a manual.

On our JLs, we're pretty much stuck with crappy 2-3 gear spacing. My plan is 5.13 or higher gears. My 2nd gear now becomes a tall first, and 3rd to 6th becomes a close ratio non-overdrive 5-speed.

Sorry - delayed reply! Yeah gotcha. I think I meant to say switch out the clutch, to have that awesome “old school” clutch feel, and then the differential to help with the gear spacing. (I’m not much of a gear-head so get these things confused often…) That would seem to significantly improve the overall MT driving experience, no? Any idea how much those two upgrades would run? Would almost rather do that first than spend money on huge tires, lift kit, etc.

 

[Rodeoflyer]

Theres no 'old school' with this tranmission. You would have the 'feel' of a heavier flywheel... like when you release the clutch at lower rpm less of a 'stall' feel and less rpm loss if that makes sense.

Gear spacing sucks and that won't be improved.. the heavier flywheel will make it feel like less of a gearing issue.

Imagine throwing something really heavy on a rubber band spring.. the heavier rubber band makes it seem like its not as heavy or far... you won't lose as much rpm into the next shift.

 

[Cutterone]

The shop installing my CF2 took 2 hours to get it bled properly, and today struggled with getting the new hydraulics installed and flowing, mainly the new slave cylinder I think. But he did say its an impressive kit, very high quality. Now lets see if they installed it correctly when I get it back, I'm really nervous!!! I'm praying it drives like a dream now...

 

[Rodeoflyer]

I really think these clutch kits will be much improved over the factory but it won't be magical in the feel/improvement with a rubicon and 5.13 gears like my situation. It will prob be a bigger deal for the sports/3.45 gear guys.. whether in a positive or negative yet to be seen.

They will be BEYOND a doubt more durable

I kinda like the dual friction feel with the gears.. it locks up quick and fantastic even at low speed with 5.13's but offroad the added flywheel mass would be great

 

[Cutterone]

What really sticks out to me, as I've mentioned before, is the OEM clutch is only rated at 272 ft/lbs, a mere 12 ft/lbs overhead of the 260 ft/lbs the Pentastar puts out. That seems like cutting it way to close, but that could be my lack of knowledge on the subject. The CF2 is rated at 430 ft/lbs, a beast in comparison and should handle anything you throw at it in stride...

 

[Rodeoflyer]

that doesn't matter. it's relative some manufacturers use different parameters.

But yes, the CF is MUCH more beefy...

 

[Cutterone]

that doesn't matter. it's relative

Ok, I'll admit I don't know the overhead most clutches have, just seems too close for comfort!

 

[Rodeoflyer]

Yes, theres likely no comparison lol.

 

[Cutterone]

In theory, couldn't one do an intake, exhaust, tune, and exceed the stock clutch holding capacity? Perhaps why you can't get manual with the 2T, its 295 ft/lbs is too much for the clutch...

 

[Cutterone]

I'm just looking for positive reinforcement that putting the CF2 in my Sahara was a smart move even before clutch problems...

 

[Rodeoflyer]

It wasn't a bad move so yeah.. smart move

 

[Cutterone]

It wasn't a bad move so yeah.. smart move

I will join you in celebration when I get the Jeep back and its functioning properly...

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