Clutch Recall (2/23/23): Clutch Pressure Plate May Overheat -- Affecting 70,000 Manual Jeep Wranglers and Gladiators

[ACTman]

I agree that nearly all of these are user induced however, based on my experience the easy stall low torque dual-mess setup combined with the long mushy break-in period exacerbates clutch abuse. I still firmly standby my theory that the dual-mass makes stalling far more likely and stall avoidance is why people slip it excessively.

I wonder how difficult it would be to weld up the dual mass and test this theory.

Don't bother. The dual-mass has nothing to do with the drivability. I haven't measured it, but less just say there is 20 degrees of rotation of damping in the flywheel, or 5% of one revolution. As you engage the clutch at 1500 rpm (for example), which is 25 rev/second, to bottom out 20 degrees of damping in the flywheel takes .05 seconds. Bottom-line: it happens too quick to be an influence on the drivability.

The reduced inertia does affect it though, since it has about 20% less inertia compared to the predecessor, the JK. Add inertia to the JL/JT and a predicable pedal feel and it vastly improves the drivability and make for a better driver experience.

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[ACTman]

@ACTman I appreciate you openly sharing so much of your data. Cause aside, PP shouldn't be failing so badly that it blows a hole in the bell housing. Totally unacceptable mechanism of failure, IMHO, regardless of pathology. FWIW, I've had zero issues with my OE clutch, even though it behaves more like race clutches I've used than a comfy DD clutch. Such crappy clutch experience on the stock clutch.

There are a lot of cars that would have exploding clutches if allowed to slip long enough. You can find videos of them on the internet. Could it be prevented by design? IMHO, absolutely. Should 100% clutch explosion prevention be a design requirement for vehicle manufacturers? One would think so, but it would likely be a new requirement.

I don't think people realize how much slipping it takes for a clutch to get hot enough for the castings to fracture like we are seeing. This is not just a matter of poor driving habits taking off from a stop light and slipping the clutch for a second or two too long. The clutch would have to be slipping for 10's of seconds under load.

 

[Rahkmalla]

WTF?, If you had to "pump" your clutch pedal, then your master cylinder HAS given up the ghost.

i didn't have to pump it. it didn't regain any pressure, it was just so light my natural reaction was to pump it fruitlessly.

 

[jimbom]

I just don't get why some folks want a stiff, heavy clutch that makes your leg ache after 30 mins of stop and go traffic. I once had an Infiniti G37 that would have made many here very happy.

On the contrary, my Gladiator and Civic are a joy to shift.

 

[Ryan...]

I just don't get why some folks want a stiff, heavy clutch that makes your leg ache after 30 mins of stop and go traffic. I once had an Infiniti G37 that would have made many here very happy.

On the contrary, my Gladiator and Civic are a joy to shift.

I'm perfectly fine with a light pedal, but if it had just a *hint* of feeling that would be great. I do appreciate the lightness on the rare occasion I get stuck in traffic

 

[DanW]

WTF?, If you had to "pump" your clutch pedal, then your master cylinder HAS given up the ghost.

Wow, yeah. That's a major problem and a candidate for a roadside weenie roaster if it needed to be pumped even once.

Maybe mine is defective. It isn't that light. It's lighter than my JK or Vette, but not so light that it has no feel. It feels perfectly fine and normal to me. Even though clutch effort is light. I finesse this Jeep easily off-road, and it's a joy in that case, too.

 

[Rahkmalla]

I just don't get why some folks want a stiff, heavy clutch that makes your leg ache after 30 mins of stop and go traffic. I once had an Infiniti G37 that would have made many here very happy.

On the contrary, my Gladiator and Civic are a joy to shift.

There exists a world between thinking your master cylinder is leaking and making every day left leg day.

 

[ACTman]

Maybe mine is defective. It isn't that light. It's lighter than my JK or Vette, but not so light that it has no feel. It feels perfectly fine and normal to me. Even though clutch effort is light.

17-19lbs is really light for a clutch pedal, but the return stroke concerns me more. We have measured less than 2 lbs on the return stroke pushing against your foot which is hardly enough to feel. See tests from 3 different Jeeps:

 

[DanW]

17-19lbs is really light for a clutch pedal, but the return stroke concerns me more. We have measured less than 2 lbs on the return stroke pushing against your foot which is hardly enough to feel. See tests from 3 different Jeeps:

Ok, but when I'm talking about feel, I'm talking about more than just the clutch itself, but the entire feel you get when you engage it and make the vehicle move. I've had no trouble with precision in tight spaces, on hills, pulling my boat, or whatever. No stalls, no surprises. It's light, but consistent. Maybe I've got a sensitive foot/leg. But friends and family who drive my Jeep seem to have no trouble, either and don't complain about it. My kids, who are beginners and learned on my JK have no trouble with it, either. My 16 y/o girl actually prefers it to the JK.

Clearly it bothers some. I've not driven another. Only mine. Maybe mine somehow was right from the get-go. But I bounce every week from JK to JL to Corvette. No issues going from one to the other and back.

Is the level of consistency between the 3 Jeeps in that graph unusual? Seems to be one that is an outlier, if I read it correctly.

 

[RubiAR]

17-19lbs is really light for a clutch pedal, but the return stroke concerns me more. We have measured less than 2 lbs on the return stroke pushing against your foot which is hardly enough to feel. See tests from 3 different Jeeps:

Yeah, I'm pretty sure my 6.7 Cummins was around 45-50lbs with an aftermarket dual disk. No whimp could steal it, that's for sure.

 

[Geoarch]

Wow, yeah. That's a major problem and a candidate for a roadside weenie roaster if it needed to be pumped even once.

Maybe mine is defective. It isn't that light. It's lighter than my JK or Vette, but not so light that it has no feel. It feels perfectly fine and normal to me. Even though clutch effort is light. I finesse this Jeep easily off-road, and it's a joy in that case, too.

That's pretty much my experience, particularly coming from a 2018 TRDPro with a "normal" clutch. And as bad as the JTR reverse gear ratio is, it was worse on the Tacoma. My 2022 JTR is a dream, including rock crawling here in New Mexico and all over the Southwest.

 

[ACTman]

Ok, but when I'm talking about feel, I'm talking about more than just the clutch itself, but the entire feel you get when you engage it and make the vehicle move. I've had no trouble with precision in tight spaces, on hills, pulling my boat, or whatever. No stalls, no surprises. It's light, but consistent. Maybe I've got a sensitive foot/leg. But friends and family who drive my Jeep seem to have no trouble, either and don't complain about it. My kids, who are beginners and learned on my JK have no trouble with it, either. My 16 y/o girl actually prefers it to the JK.

Clearly it bothers some. I've not driven another. Only mine. Maybe mine somehow was right from the get-go. But I bounce every week from JK to JL to Corvette. No issues going from one to the other and back.

Is the level of consistency between the 3 Jeeps in that graph unusual? Seems to be one that is an outlier, if I read it correctly.

Let me explain the graph a bit more. The blue lines (the outlier) represent testing we did on a brand new Jeep on the showroom floor. The gray and green are after 21K and 62K miles, respectively. Both were fair-weather cars btw. The difference between the down stroke and up stroke is friction. The pedal is always going to be stiffer going down that up since friction adds to the load going down and subtracts from the load going up.

The total amount of friction over time on the JL/JT is not that unusual, but the amount of friction versus load is. The pedal is still very light going down but is in fact over 6 times stiffer going down than returning at the middle to lower part of the pedal travel.

I didn't find the stock JL/JT clutch difficult to manage either. You just have to adjust to referencing pedal travel, and forget about pedal load in order to drive it.

 

[seven30]

I'm perfectly fine with a light pedal, but if it had just a *hint* of feeling that would be great. I do appreciate the lightness on the rare occasion I get stuck in traffic

Its good to make that distinction. Mine did much improve after 4k or so. Never had a clutch take that long to bed in before.

 

[Nance146]

FYI, ACT clutches are 30% off until Nov 30 for anyone on the fence. A little over $200 in savings over standard pricing.

Idk if I can ever get used to the light weight flywheel. There is just too much throttle modulation for my liking. I also don’t think there will ever be a proper fix to the issue because that would be accepting blame imo. Went with the JP6. Fingers crossed I won’t regret it.

 

[jimbom]

17-19lbs is really light for a clutch pedal, but the return stroke concerns me more. We have measured less than 2 lbs on the return stroke pushing against your foot which is hardly enough to feel. See tests from 3 different Jeeps:

So this is all about the spring force, not the friction material, the wear, the throw out bearing feel or anything else.

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