JL 3.6 Manual Transmission Clutch.... Please ELI5

[M_Pluto]

A heavy rotating mass (like a flywheel) will be harder to slowdown and harder to spin faster than a lighter rotating mass, all else equal. Race cars often use light weight flywheels because they can be accelerated and decelerated more easily than a heavier flywheel (think high RPMs with lots of shifting, low to high RPMs and vice verse). In contrast a heavier flywheel will keep spinning, be harder to stop (think resisting stalling).

Centerforce flywheel is heavier than OEM. That is all.

Apparently I spoke too soon. Thank you for your response, I was hoping for a reply like this. It sounds like no matter what, a centerforce clutch would do me good to install, especially on a vehicle that might be driven in a low gear when doing something like rock crawling.... Okay, I think I'm starting to get it. Thank you!

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[word302]

So the Rubicon is detuned or the Sahara/sport is? I'm not clear on what you're trying to say.

Sorry for the typo, I was responding to 2 different statements that you made.

1. None of the motors have been detuned.

2. If you have a sport or Sahara you have 3.45 gearing in the axles, which is pretty terrible when paired with the manual transmission. If you add bigger tires it’s even worse.

 

[bjm00se]

...it sounds like no matter what, a centerforce clutch would do me good to install,...

I'm not completely convinced that's correct. Based on the threads I've seen, Centerforce releases a clutch for the JL, a few people buy it, there are some problems, they stop selling it, and announce a "new improved design" to be released a little later. I think this has happened like three times now for the JL.

Am I reading it wrong?

We all know how perception warps reality on the Internet. A few cases of problems on JL clutches have created an echo-chamber perception that JL factory clutch is problem prone, dangerous, or just hard to use.

I swear, it's like Nickleback. You can't be on the Internet without hating the JL 6 speed and clutch.

So, many of us can't help but to weigh in with our counter-experience of "no problems here."

But back to the point - the same level (actually higher) of "anecdotal evidence" that damns the factory clutch seems to me to indicate that the Centerforce clutch is still getting the bugs worked out.

Not to mention, it's an expensive upgrade, unless you're the type who is so mechanically inclined that you think nothing of replacing a clutch as a Saturday DIY project. (even then, it's over a thousand bucks in parts)

I find that the factory clutch provides a little less tactile feedback than I'd ultimately prefer, and if it were to fail, I'd give strong consideration to replacing it with a Centerforce, but I do think this is a case of "if it ain't broke, don't fix it."

 

[fdFifty]

I could go on for quite a long time about possible causes for the clutch issues. But I honestly don't think anyone (yes this is jeep engineers included) have a great grasp on what's going on with them. People who have issues at all seem to have them in widely different levels of severity. I tried for a very long time to get to the bottom of issues I had with mine but could never find a concrete solution. There honestly just isn't a consistent enough data set for anyone to work from.

However, I think centerforce may be very close to having a comprehensive solution with their latest generation clutch with included hydraulics. I had their first gen dual friction and it improved feel and off road drivability a lot. But I still had constant problems with sticky gears, squeaky hydraulics, low speed engagement chatter, along with a myriad of other little things. My gut feeling was that the hydraulics were mostly responsible for this but never reached a lasting fix to know for sure.

Do I think it was at risk of blowing up at any given second? No. But did I find it pleasant or fun to drive? Not really. And that's why I eventually sold it and got another with the 8 speed. The whole reason for driving a manual is to have a connection to the drive and this set up just never did it for me.

My advice would be to test drive this specific 6 speed and see how you like it. If you enjoy how it drives then I'd say roll with it. There are many people who have had no issues and like their manual JL a lot. There's clearly something going on with some of these but I don't know if that alone is enough reason to avoid it altogether.

 

[fdFifty]

Not sure where everyone is getting the whole "dual disc" thing from, it's a single disc still. Dual mass flywheel, with a normal diaphragm clutch and single disc.

Do you know if they revised this design at any point? I'm definitely not a Dual Mass Flywheel expert but the stock clutch that came from my 2019 looks like it has two separate friction discs. One looks like its tucked up into the pressure plate and isn't readily assessable unless you grind some of the dowels down.

I've been trying to wrap my head around this set up for a while so I'm just genuinely curious if they've been revised or if it's not a second disc in there after all.

 

[No14]

First Jeep order here, Also went for MT. Didn’t know about any issues before until seeing this thread (I guess I didn‘d do a good job with my homework apart from test-driving both)… still doesn’t sway me. That ZF-8 is solid and was surprised to find out that Jeep uses that. Wife’s BMW also has ZF-8 and its a very good transmission. Other car is also a BMW with dual clutch transmission (talk about edge of your seat gear changes). Decided to go back to a proper 3-pedal set up.
JL MT does have it’s quirky pedal feel, not a deal breaker….
I have my reasons for going manual, and sticking with that.

thanks for all the info about what to watch out for and possible MT failures tho.
Good luck to OP... And me

 

[M_Pluto]

However, I think centerforce may be very close to having a comprehensive solution with their latest generation clutch with included hydraulics. I had their first gen dual friction and it improved feel and off road drivability a lot. But I still had constant problems with sticky gears, squeaky hydraulics, low speed engagement chatter, along with a myriad of other little things. My gut feeling was that the hydraulics were mostly responsible for this but never reached a lasting fix to know for sure.

So far as I could tell, they are only on revision 2? Or at least, that's the only revision they've released?

 

[desmo2]

'21 MT 3.6L Rubicon 2-door. Loving all of it so far.

Wouldn't change a thing.

 

[fdFifty]

So far as I could tell, they are only on revision 2? Or at least, that's the only revision they've released?

Yeah I think only 2 production revisions for the centerforce kits. I know they had sort of a version 1.5 friction disc that they were evaluating/testing but I don't think that was ever available to the masses.

The included replacement hydraulic components were the missing piece of the puzzle for a long time and I believe those are now available. Those will provide the most ideal cylinder stroke/travel for the centerforce components. I don't think the stock components provided quite enough travel for the clutch to fully disengage. Hence the sticky shifting and other oddness some experience.

The other technical detail to note is that the centerforce hydraulics come with heat shielding. On the JL the clutch release cylinder is located right next to the driver side catalytic converter. Always suspected that heat from the converter was cooking the fluid and possibly seals on the cylinder itself. Never had hard proof but it's interesting to see that centerforce added that shielding.

Hopefully that's not too much technical babble but can be something more in line with the info you're after.

 

[M_Pluto]

'21 MT 3.6L Rubicon 2-door. Loving all of it so far.

Wouldn't change a thing.

While that's great to hear, that is not what I'm asking what you think of your MT in this thread. I'm asking if someone can explain the clutch system to me. Can you do that? If not, stay out please.

 

[M_Pluto]

Yeah I think only 2 production revisions for the centerforce kits. I know they had sort of a version 1.5 friction disc that they were evaluating/testing but I don't think that was ever available to the masses.

The included replacement hydraulic components were the missing piece of the puzzle for a long time and I believe those are now available. Those will provide the most ideal cylinder stroke/travel for the centerforce components. I don't think the stock components provided quite enough travel for the clutch to fully disengage. Hence the sticky shifting and other oddness some experience.

The other technical detail to note is that the centerforce hydraulics come with heat shielding. On the JL the clutch release cylinder is located right next to the driver side catalytic converter. Always suspected that heat from the converter was cooking the fluid and possibly seals on the cylinder itself. Never had hard proof but it's interesting to see that centerforce added that shielding.

Hopefully that's not too much technical babble but can be something more in line with the info you're after.

it's the exact technical talk I was asking for, so thanks! I just need it explained like I was 5 and in more layman's terms because some of the jargon gets lost on me.

Do you think there is much more tuning left to do with v2 (saying this knowing perfection is never any option, but are they close enough now?)?.

Interesting about the heat shielding, it's entirely possible that lacking any on the OEM would definitely be a contributing factor in my eyes (from my very limited knowledge at least! ).

 

[desmo2]

If not, stay out please.

Well, then. I guess I'll be a-steppin'. Adios.

 

[Tncdrew]

While that's great to hear, that is not what I'm asking what you think of your MT in this thread. I'm asking if someone can explain the clutch system to me. Can you do that? If not, stay out please.

Just... WOW!
Maybe it's time you do a little internet research, or try searching YouTube for videos on the operation of a clutch system.... no?

 

[SteadyC]

I am not an expert either, but I have been searching since your post. I have a mt and love it, never had any issues, and haven’t done either recall as I fear risk with dealership introducing issues in my perfectly operating clutch. I did 3 of the 4 parts of the first recall myself, remove the clip, inspect the fluid hose, and dump test. Ok, I didn’t actually do the dump test, but I know it’s not slipping and would pass. Also, my wife kills it a lot going up our steep driveway, . The primary premise to the first recall was air entered the fluid system, allowing the clutch to,slip and generate heat.

what I find interesting, is the concept that ours is a dual mass flywheel, from another blog about our clutch.
Google " Dual Mass Flywheel ", read and weep.
It's a big trade off in reliability and cost over the single mass flywheel, plus the torque range of the dual mass is specific and narrow.

Read this from an external source
https://www.phoenixfriction.com/t-symptoms-of-dual-mass-flywheel-failure.aspx
Like a lot of the parts on the modern automobile, dual mass flywheels are a compromise. On the plus side, dual mass flywheels reduce the torsional vibrations in the driveline and the other related vibration and noises. On the negative side, dual mass flywheels are expensive and more prone to failure than simpler, single mass systems (especially if a vehicle is modified to have increased torque).

Single mass conversion kits replace a dual mass flywheel with a simpler, more robust system. While a single mass system will be a bit noisier* than a dual mass system, it will also be more reliable, especially in high torque/low idle rpm applications.

this is what the CF is doing. high torque low RPM sounds like we do off-roading, maybe.low rpm for sure.

im sure FCA went with the dual mass for that improved driver experience like in other parts of our jeep.

so I think the key is just understand dual mass system, to answer your direct question.

 

[Xtina]

Sorry for the typo, I was responding to 2 different statements that you made.

1. None of the motors have been detuned.

2. If you have a sport or Sahara you have 3.45 gearing in the axles, which is pretty terrible when paired with the manual transmission. If you add bigger tires it’s even worse.

Ya I have the Willys. So the 3.45. And yes it's crap lol

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