Centerforce Clutch Installed on JL Rubicon

[DanW]

Just for the record, with the CF, the dual mass flywheel and twin-disc clutch are replaced with a traditional flywheel and single clutch, thereby completely eliminating any chance of such a failure. It's possible to make such a bold statement as having a pressure plate scatter is pretty much an unheard of failure among any clutch, especially a traditional single disc unit. Maybe somewhere in the world at some time it's happened, but neither I nor anyone I know has never heard of it occurring. At worst, when a clutch fails, you get a smoking molten goo and no transfer of power

Even Centerforce's friction plate won't handle 1100 to 12oo degrees, which is the temp range the factory pressure plates that had failed were determined to have reached. The pressure plate itself is not the problem. I hope it never happens to a CF customer, but time will tell. Haven't heard of one yet. But there are just so few out there.

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[LLRubylady]

what is a normal operating temp for a clutch anyway?
and why is it that the oem gets to 1100 degrees?
i read that it is suspected with the overheating fluid but wonder what else it could be?

 

[DanW]

what is a normal operating temp for a clutch anyway?
and why is it that the oem gets to 1100 degrees?
i read that it is suspected with the overheating fluid but wonder what else it could be?

It got to 1100 degrees from excessive slipping when the original problem was in play. They get nowhere near that in normal conditions. I've hit my bell housing near the clutch with an infrared thermometer after hard driving and it wasn't even 180. Being aluminum, which is a great conductor, that means that what was on the other side wasn't that much hotter.

 

[LLRubylady]

It got to 1100 degrees from excessive slipping when the original problem was in play. They get nowhere near that in normal conditions. I've hit my bell housing near the clutch with an infrared thermometer after hard driving and it wasn't even 180. Being aluminum, which is a great conductor, that means that what was on the other side wasn't that much hotter.

Yikes-well you got to that temp but yours didn’t blow. Are you on the original clutch or did you get a fix?
only time will tell if the CF’s hold up. I hope so for those that installed it.

 

[BuyHold]

It's a good theory, but in reality, brake fluid boils when hot rather than expands, resulting in aeration which reduces it's ability to exert force

Typically, for a given mass of liquid/fluid, the gaseous state would yield a larger volume than in liquid state. Think steam vs fluid water.

 

[nomographer]

Gasses are considerably more compressible than liquids, however, it's not clear what the pressure limit is in this system, and it's easier for larger volumes of gas to escape (but arguably not so for small bubbles since bleeding has been an issue). Even as a liquid however:

https://www.sciencedirect.com/topics/engineering/brake-fluid

Brake fluids have been studied in depth for many years, especially since overheating used to lead to more obvious failures.

 

[Toycrusher]

Even Centerforce's friction plate won't handle 1100 to 12oo degrees, which is the temp range the factory pressure plates that had failed were determined to have reached. The pressure plate itself is not the problem. I hope it never happens to a CF customer, but time will tell. Haven't heard of one yet. But there are just so few out there.

The weak point of a clutch is the friction material. At 500 to 700 degrees your average clutch turns into a cloud of acrid smoke and your forward momentum stops. There is no explanation as to how this pressure plate would ever make it to 1100 degrees

 

[JeepinPete]

Just because the clutch material isn't grabbing at " 500 to 700 degrees" doesn't mean the heat from friction just ceases. The coefficient of friction of the clutch material falls off, but it doesn't go to zero. There is still force from the pressure plate squeezing everything together which causes more heat.

The pro's to this clutch design are light weight and increased clamping force of a given spring load. Jeep chose to lighten the clamping force which gives us the light clutch pedal.

The tradeoff on the dual disc clutch is the secondary pressure plate has a tiny mass compared to the flywheel. On top of that the heat doesn't have any great way of moving out of the secondary pressure plate. If you slip it much, the heat in the secondary pressure plate will climb all of of proportion compared to the flywheel in a standard single disc clutch.

Pete

 

[Toycrusher]

Again, you should be suffocating from a cloud of toxic smoke waaaaay before you are able to hit 700 degrees, much less 1100 degrees anywhere in the clutch assembly

 

[DanW]

Again, you should be suffocating from a cloud of toxic smoke waaaaay before you are able to hit 700 degrees, much less 1100 degrees anywhere in the clutch assembly

There was a forensic/metalurgy report from FCA and I believe NHTSA that determined that in the cases where the friction plate came apart, it had been heated to 1100+ degrees from excessive slipping, damaging it and leading to the failure. I don't have a link but I did read it.

Bottom line: No friction plate in any mass produced manual transmission is designed to handle that kind of heat. From what my nephew who owns a racing engine building company tells me, there aren't any he's seen in racing that are designed to handle that, either. Of course, most components in the racing transmissions are actually less stout because they aren't designed to last very long.

 

[Toycrusher]

There was a forensic/metalurgy report from FCA and I believe NHTSA that determined that in the cases where the friction plate came apart, it had been heated to 1100+ degrees from excessive slipping, damaging it and leading to the failure. I don't have a link but I did read it.

Bottom line: No friction plate in any mass produced manual transmission is designed to handle that kind of heat. From what my nephew who owns a racing engine building company tells me, there aren't any he's seen in racing that are designed to handle that, either. Of course, most components in the racing transmissions are actually less stout because they aren't designed to last very long.

Which, again, begs the question, WHY is the pressure plate the weak point rather than the friction material? Every other clutch reaches end-of-life status when the friction material can no longer transfer sufficient torque. This is almost always accompanied by heat and smoke, not fracturing pressure plates.

Not that I would ever want to go back to stock, but Jeep should have just ponied up and replaced the clutch assemblies rather than program in the detune bandaid. It's obvious which route was cheaper

 

[LLRubylady]

We still don’t know if the new part “AD” is sufficient. We can not guess if the newer jeeps that have had the explosion had that part or not.
oh well, time for a new Jeep for me.

 

[word302]

Which, again, begs the question, WHY is the pressure plate the weak point rather than the friction material? Every other clutch reaches end-of-life status when the friction material can no longer transfer sufficient torque. This is almost always accompanied by heat and smoke, not fracturing pressure plates.

Not that I would ever want to go back to stock, but Jeep should have just ponied up and replaced the clutch assemblies rather than program in the detune bandaid. It's obvious which route was cheaper

Because replacing all the clutches for a minuscule failure rate would be silly.

 

[Toycrusher]

Because replacing all the clutches for a minuscule failure rate would be silly.

Most recalls are over minuscule failure rates, why should this be any different?

 

[LLRubylady]

It’s true that most people will not experience any clutch problems and mine has been ok. It’s just nerve wracking to think at any moment boom. It’s affecting my enjoyment so gotta go.
it’s unfortunate.

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