JT/JL Clutch and Flywheel explained by ACT

[ACTman]

I installed the ACT clutch with the Promass flywheel today, and when I drove it away, the slave cylinder blew. I hope a new one last a while.

This is usually caused by the slave cyl not connecting with the clutch arm correctly. It is so common AllData instructs to use a scope to make sure it is installed correctly. It should be fine just make sure it is installed right.

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[Geoarch]

This is usually caused by the slave cyl not connecting with the clutch arm correctly. It is so common AllData instructs to use a scope to make sure it is installed correctly. It should be fine just make sure it is installed right.

Thanks. That makes sense.

 

[mtbjeeper]

@ACTman and the other contributors in this thread and the numerous other clutch threads: First off thanks for all the time and information, it is really appreciated. Sorry if this will be a longish post but please read.

My quick backstory: I’ve been a JL MT owner for six years, no issues very happy outside of stalling from time to time as if I hadn’t been driving a manual for 30 years. An upgraded clutch has been on my radar since day 1. My JL never had recall work done to the clutch, which is now close to 70,000 miles with plenty of off-road time.

I very recently purchased a used 2020 MT Gladiator (really happy about that) and I have an ACT clutch sitting in my house awaiting install as I am really focused on making this build the best that I can. So, on maybe my sixth time driving this new to me vehicle, in heavy traffic outside of NYC, I received my first ever Clutch Overheat Warning.

I was pretty rattled as I have seen the reports of fires etc. and as I was in heavy traffic with no shoulder present I had nowhere to go but forward. I focused on cleaning up my typically lazy traffic-based clutch work, made it to my exit and the warning display stopped. As you can imagine this episode led to a whole bunch of Google time.

Best I can tell is the vehicle computer uses some type of fuzzy math taking rotational speeds and gear selection into account to determine if there MIGHT be slippage and as such heat build up. As far as I know there is no actual temperate sensor in the clutch.

So my question for those in the know is will this warning display and possible subsequent limp mode continue after the ACT clutch install? While the new clutch may be better equipped to handle heat build-up, the computer still uses the same logic and has no idea that there is a different clutch in the vehicle. So will the warning display and limp mode persist even after the clutch is upgraded?

One additional question: several people online have surmised that a series of slave cylinders were not fully bled from the factory. As such when the pedal is all the way down the clutch is not fully disengaged allowing heat build up. During heavy traffic this could lead to a lot of additional heat but how would the computer know that without an actual temperature sensor? Also could this be true about the slave cylinder? Can the slave cylinder be bled? Should I replace it as part of the clutch upgrade?

Sorry for the long post but I’m really interested in hearing your educated answers.

Thanks you,

Mike

 

[mrhemi]

Does anyone know if the stock factory clutch slave cylinder, or the hydraulic line, have what is known as the "Clutch Delay Valve" in place? This is installed in all manual trans. Dodge Challengers and contributes to vague, inconsistent clutch feel. I have searched and cannot find any reference to it in Jeep forums. In the case of the Challengers, it is easily removed and vastly improves clutch operation.

 

[seven30]

@ACTman and the other contributors in this thread and the numerous other clutch threads: First off thanks for all the time and information, it is really appreciated. Sorry if this will be a longish post but please read.

My quick backstory: I’ve been a JL MT owner for six years, no issues very happy outside of stalling from time to time as if I hadn’t been driving a manual for 30 years. An upgraded clutch has been on my radar since day 1. My JL never had recall work done to the clutch, which is now close to 70,000 miles with plenty of off-road time.

I very recently purchased a used 2020 MT Gladiator (really happy about that) and I have an ACT clutch sitting in my house awaiting install as I am really focused on making this build the best that I can. So, on maybe my sixth time driving this new to me vehicle, in heavy traffic outside of NYC, I received my first ever Clutch Overheat Warning.

I was pretty rattled as I have seen the reports of fires etc. and as I was in heavy traffic with no shoulder present I had nowhere to go but forward. I focused on cleaning up my typically lazy traffic-based clutch work, made it to my exit and the warning display stopped. As you can imagine this episode led to a whole bunch of Google time.

Best I can tell is the vehicle computer uses some type of fuzzy math taking rotational speeds and gear selection into account to determine if there MIGHT be slippage and as such heat build up. As far as I know there is no actual temperate sensor in the clutch.

So my question for those in the know is will this warning display and possible subsequent limp mode continue after the ACT clutch install? While the new clutch may be better equipped to handle heat build-up, the computer still uses the same logic and has no idea that there is a different clutch in the vehicle. So will the warning display and limp mode persist even after the clutch is upgraded?

One additional question: several people online have surmised that a series of slave cylinders were not fully bled from the factory. As such when the pedal is all the way down the clutch is not fully disengaged allowing heat build up. During heavy traffic this could lead to a lot of additional heat but how would the computer know that without an actual temperature sensor? Also could this be true about the slave cylinder? Can the slave cylinder be bled? Should I replace it as part of the clutch upgrade?

Sorry for the long post but I’m really interested in hearing your educated answers.

Thanks you,

Mike

I have 70K on a MT JT. Stock clutch. Cams failed before clutch! When new the twin disc clutch is pretty vague and mushy which combined with low torque engine and dual mass flywheel means your going to slip it a lot trying to avoid stalling.

It took my clutch 1k miles before it was "normal" and 4k to completely breakin.
But now the clutch is excellent with good control and light pedal. No overheat even backing a trailer or crawling rocky trails.

After far as the warning goes the ecu uses engine and output shaft rpm to calculate slippage and infer heat.

 

[mtbjeeper]

After far as the warning goes the ecu uses engine and output shaft rpm to calculate slippage and infer heat.

My JT has 32,000 miles on it. I bought it used and have only put about 600 miles on it. One of those miles threw a Clutch Overheat message. My concern is that the warning and limp mode protection will still persist after the original clutch is replaced. The ECU has no idea that a different clutch has been installed. Correct?

 

[Birds83]

My JT has 32,000 miles on it. I bought it used and have only put about 600 miles on it. One of those miles threw a Clutch Overheat message. My concern is that the warning and limp mode protection will still persist after the original clutch is replaced. The ECU has no idea that a different clutch has been installed. Correct?

I’ve only had the overheat light once pre act clutch and none since(recall was done prior to Jeep purchase new). Can’t say why or why not. Mine set it doing heavy beach driving without using the clutch I can think maybe I overheated it cause it was slipping in thick sand with my 35s due to poor design but that’s just a guess.
I am battening a service transmission light due to the recall and my larger tires but that’s another story.

 

[seven30]

My JT has 32,000 miles on it. I bought it used and have only put about 600 miles on it. One of those miles threw a Clutch Overheat message. My concern is that the warning and limp mode protection will still persist after the original clutch is replaced. The ECU has no idea that a different clutch has been installed. Correct?

No clutch is designed to slip much. The low torque V6 tends to encourage slipping. You have to practice keeping the clutch right at lockup with minimal slipping. If you find yourself keeping rpm up and using the clutch to control power that is guaranteed to overheat the clutch.
And yes, the ECU monitors engine and transmission rpm and throttle to estimate heat.

 

[mtbjeeper]

No clutch is designed to slip much. The low torque V6 tends to encourage slipping. You have to practice keeping the clutch right at lockup with minimal slipping. If you find yourself keeping rpm up and using the clutch to control power that is guaranteed to overheat the clutch.
And yes, the ECU monitors engine and transmission rpm and throttle to estimate heat.

So assuming that a well designed aftermarket clutch slips less than the stock clutch is prone to, the ECU shouldn’t throw up any warnings. Sound about right?

The higher clamp force of an aftermarket clutch should resolve slippage at highway speeds where the failures seem to be occurring. My only concern is slow speed operation on road where we use the clutch to modulate speed in bumper to bumper traffic., or hold the vehicle still at a traffic light without the brake. During these times we use slippage to our advantage, as we have for over a hundred years. The ECU’s not going to like that. Is the only option to drive it more like an automatic?

I’m sold on the ACT clutch for drivability, especially off road, but I don’t think it resolves the overheat warning and limp mode issues unless we/I change the way we drive.

But maybe I’m missing something or maybe I’m the worst manual driver of all time and I finally have a vehicle with a computer that will happily tell me so.

 

[bd100]

My only concern is slow speed operation on road where we use the clutch to modulate speed in bumper to bumper traffic., or hold the vehicle still at a traffic light without the brake. During these times we use slippage to our advantage, as we have for over a hundred years.

In bumper to bumper traffic either shift to neutral and coast or leave the clutch fully engaged and let the gap grow and shrink to compensate. It's easy to do and stop 'n go traffic is fine this way. And at a traffic light hit neutral and use the brakes. Much easier on the system, and much easier to service!

 

[BuffaloSoldier]

Thank you for your post. It has answered a lot of questions that I had.

 

[Birds83]

So assuming that a well designed aftermarket clutch slips less than the stock clutch is prone to, the ECU shouldn’t throw up any warnings. Sound about right?

The higher clamp force of an aftermarket clutch should resolve slippage at highway speeds where the failures seem to be occurring. My only concern is slow speed operation on road where we use the clutch to modulate speed in bumper to bumper traffic., or hold the vehicle still at a traffic light without the brake. During these times we use slippage to our advantage, as we have for over a hundred years. The ECU’s not going to like that. Is the only option to drive it more like an automatic?

I’m sold on the ACT clutch for drivability, especially off road, but I don’t think it resolves the overheat warning and limp mode issues unless we/I change the way we drive.

But maybe I’m missing something or maybe I’m the worst manual driver of all time and I finally have a vehicle with a computer that will happily tell me so.

boils down to the computer not being happy. Doesn’t happen all the time but does happen…. At least for me.
Best option to fix that part is to send pcm out for pre recall software so it stops all that BS all together.

 

[msugeek]

or hold the vehicle still at a traffic light without the brake.

Wait, what? People do this?? Good way to burn a clutch out real quick.

 

[HenrytheDestroyer]

boils down to the computer not being happy. Doesn’t happen all the time but does happen…. At least for me.
Best option to fix that part is to send pcm out for pre recall software so it stops all that BS all together.

do you have a lead on pre-recall software to do this?

I’m bummed that aftermarket clutches which presumably fix Jeep’s initial failings are still subject to the half assed nanny fixes they attempted rather than make a good system in the first place.

 

[Birds83]

do you have a lead on pre-recall software to do this?

I’m bummed that aftermarket clutches which presumably fix Jeep’s initial failings are still subject to the half assed nanny fixes they attempted rather than make a good system in the first place.

See photo it’s Hemi-fast. I think I’ve seen 1 person say they sent out and got it back and worked great so far been a few weeks.

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