beaups

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I have been thru both of the the forums about the clutch recall. I understand the temperature will be a "calculation" based on other readings form the vehicle. I have not seen anything in the thread about tire size. This has a HUGE effect on the calculation. I have a Sahara and put on the Rubi Wheels and tires, I have not make the change to the ECU -- Threrefore, the Jeep is going faster then it really is ! I would assume this will cause problems with the calculation. Am I wrong ?? If not, then the dealer will need to mkae the update for the tire size, AND in the future when you change tire size it will cause problems ! ! Again, please someone correct me if I am wrong.
The ECU will see the same as stock *until* you reprogram (only a GPS knows your parameters are incorrect). So, no, there would not be an affect on the calculations.
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I have been thru both of the the forums about the clutch recall. I understand the temperature will be a "calculation" based on other readings form the vehicle. I have not seen anything in the thread about tire size. This has a HUGE effect on the calculation. I have a Sahara and put on the Rubi Wheels and tires, I have not make the change to the ECU -- Threrefore, the Jeep is going faster then it really is ! I would assume this will cause problems with the calculation. Am I wrong ?? If not, then the dealer will need to mkae the update for the tire size, AND in the future when you change tire size it will cause problems ! ! Again, please someone correct me if I am wrong.
You are wrong :giggle:

We don't really know how the algorithm works, but if I were writing it I would create a time series comparing engine rpm with indicated speed in, say one second intervals. I would reset the time series every time you shift to a new gear and release the clutch. Under these conditions, when you divide rpm by speed you should get a constant value, if not the clutch is slipping and you trigger limp mode and an error message.

I would also have an algorithm for when the clutch is depressed. Specifically I would look at throttle position, indicated speed and duration the clutch is depressed. This would not be a time series but a cumulative calculation of energy being transmitted to the clutch.

Bottom line is that actual road speed is not important, the algorithm is looking for 1) slippage and 2) energy transmitted through the clutch. Bigger tires or lower gears would appear the same as going up or down a slight incline.

I could be wrong, but I'm not. ;)
 
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You are wrong :giggle:

We don't really know how the algorithm works, but if I were writing it I would create a time series comparing engine rpm with indicated speed in, say one second intervals. I would reset the time series every time you shift to a new gear and release the clutch. Under these conditions, when you divide rpm by speed you should get a constant value, if not the clutch is slipping and you trigger limp mode and an error message.

I would also have an algorithm for when the clutch is depressed. Specifically I would look at throttle position, indicated speed and duration the clutch is depressed. This would not be a time series but a cumulative calculation of energy being transmitted to the clutch.

Bottom line is that actual road speed is not important, the algorithm is looking for 1) slippage and 2) energy transmitted through the clutch. Bigger tires or lower gears would appear the same as going up or down a slight incline.

I could be wrong, but I'm not. ;)

OK - maybe I started talking about "Speed" which is related, but really what is to be considered is RPMs- The RPMS of the flywheel related to the RPMS of the driveshaft. If the RPM of the Flywheel does not match the RPM of the drive shaft then you have slippageThe RPMs of the flywheel is known (engine speed) - The RPMs of the drive shaft I think is NOT known and is calculated using the data from the speedometer, tire size and gear. If someone regears or changes tire size and does NOT update the computer, then the calculation of RPMs of the driveshaft will not be accurate. Therefore the computer will think the clutch is slipping, but in reality, it is not.
 

beaups

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OK - maybe I started talking about "Speed" which is related, but really what is to be considered is RPMs- The RPMS of the flywheel related to the RPMS of the driveshaft. If the RPM of the Flywheel does not match the RPM of the drive shaft then you have slippageThe RPMs of the flywheel is known (engine speed) - The RPMs of the drive shaft I think is NOT known and is calculated using the data from the speedometer, tire size and gear. If someone regears or changes tire size and does NOT update the computer, then the calculation of RPMs of the driveshaft will not be accurate. Therefore the computer will think the clutch is slipping, but in reality, it is not.
That's still incorrect. The ECM knows the engine speed, the current gear, and the wheel speed. The important part is wheel speed sensors measure angular velocity, not linear. TLDR if you put 80" tires on your wrangler and don't reprogram anything everything looks the same to the ECM as stock as the wheel RPM has the same relationship to engine rpm as it did with the stock tires. The only thing you've changed is how *far* the vehicle travels for each rotation of the wheel, and that is invisible to the ECM (hence why the speedometer is wrong).

If you change gearing without reprogramming, that would change the expected engine RPM vs. wheel speed and *could* cause some undesired behavior depending on how they coded this update.
 

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Quick update, my ESS started working again. Back to how it was prior to the recall.
 

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A factor into why we like manuals is the low tech nature of it. It's a bummer to be relying on computers rather than mechanical components - if I wanted that, I'd opt for the automatic. It's still early days so hopefully a better clutch gets put in at some point.
 

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There's a speed sensor in the transfer case, so the wheel speed sensors aren't needed here?
 

beaups

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There's a speed sensor in the transfer case, so the wheel speed sensors aren't needed here?
Depends what sensor they are using. But either way it’s the same math, rear wheel rpm = 1/4.10 or 1/3.45 of TC output shaft speed, regardless of tire size.
 
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Kreepin1

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OK - maybe I started talking about "Speed" which is related, but really what is to be considered is RPMs- The RPMS of the flywheel related to the RPMS of the driveshaft. If the RPM of the Flywheel does not match the RPM of the drive shaft then you have slippageThe RPMs of the flywheel is known (engine speed) - The RPMs of the drive shaft I think is NOT known and is calculated using the data from the speedometer, tire size and gear. If someone regears or changes tire size and does NOT update the computer, then the calculation of RPMs of the driveshaft will not be accurate. Therefore the computer will think the clutch is slipping, but in reality, it is not.
As @nomographer pointed out, the speed sensor is located in the transfer case and directly connected to the driveshaft. I don't think changing tire size or gearing will impact the calculations. Relax.
 

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OK - maybe I started talking about "Speed" which is related, but really what is to be considered is RPMs- The RPMS of the flywheel related to the RPMS of the driveshaft. If the RPM of the Flywheel does not match the RPM of the drive shaft then you have slippageThe RPMs of the flywheel is known (engine speed) - The RPMs of the drive shaft I think is NOT known and is calculated using the data from the speedometer, tire size and gear. If someone regears or changes tire size and does NOT update the computer, then the calculation of RPMs of the driveshaft will not be accurate. Therefore the computer will think the clutch is slipping, but in reality, it is not.
as others have said your speed on the speedo is measured by a hall effect sensor on the rear output of the transfer case and then the computer makes the calculation for final drive speed depending on what size tire and gear ration you have installed to as it is a more reliable way to measure true vehicle speed (when you turn all 4 wheels turn at a different speed) and allows them to install the same drive train into different vehicles with different tire and diff gear combinations at minimal complications

there is wheel speed sensors, the abs tone rings on each axle shaft end but these are only used to detect slippage of the wheels to the abs or traction control system, it just does a comparison of wheel speed on a axle and does not factor in tire size
 

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Interesting reading this and the earlier/other recall thread. People seem to have difficulty sifting through speculation and facts, but the software change is a failsafe designed to prevent a catastrophic failure that might lead to injuries, road debris, etc., exactly as indicated in the notice.

Nothing in the notice indicates they are done, but if they spent the next eighteen months investigating having not taken this step it would be less responsible. Ask how you'd feel if another dozen exploded in the next year and "they knew all along but did nothing".

This is a very infrequent failure and many customers with problems aren't aware of it, making it very difficult for them to even investigate. If you failed the clutch dump / slip test, were they supposed to take your Jeep back to the factory to let engineers tear it apart? Do you want them to build a thousand just to drive around hoping that one of them starts failing so they can investigate? The entire business is "theoretical" (including your traction control, your ABS, even the battery charger), and the simple fact is that the hose change seemed to improve things for some customers.

Centerforce had issues, so why would Jeep think a full replacement was a solution?

Are they trying to limit costs? Sure. Could they extend our warranty? Yes, that would be a sign of good customer relations even if they had to eat a few "wear parts".

Quite simply, though, people are flying up hills in fifth gear with their tachometer sliding all over and the driver doesn't notice. Some drivers can't even tell that the ESS restart is ready to move the vehicle. Some are stalling because they should recalibrate the throttle pedal but are just popping to 4k to get started and wearing the clutch. The software is here to tell those people to get their inattentiveness to a dealer so someone can pay attention.

ps I don't have a financial interest in Jeep/FCA/Stellantis, not a lawyer, not a dealer.
Well written. Worth re-posting. As long as FCA follows with a re-designed clutch. At the end that’s the cause of the problem. People not knowing how to drive are driving other manual cars with no issue other than premature wear.
 

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Interesting reading this and the earlier/other recall thread. People seem to have difficulty sifting through speculation and facts, but the software change is a failsafe designed to prevent a catastrophic failure that might lead to injuries, road debris, etc., exactly as indicated in the notice.

Nothing in the notice indicates they are done, but if they spent the next eighteen months investigating having not taken this step it would be less responsible. Ask how you'd feel if another dozen exploded in the next year and "they knew all along but did nothing".

This is a very infrequent failure and many customers with problems aren't aware of it, making it very difficult for them to even investigate. If you failed the clutch dump / slip test, were they supposed to take your Jeep back to the factory to let engineers tear it apart? Do you want them to build a thousand just to drive around hoping that one of them starts failing so they can investigate? The entire business is "theoretical" (including your traction control, your ABS, even the battery charger), and the simple fact is that the hose change seemed to improve things for some customers.

Centerforce had issues, so why would Jeep think a full replacement was a solution?

Are they trying to limit costs? Sure. Could they extend our warranty? Yes, that would be a sign of good customer relations even if they had to eat a few "wear parts".

Quite simply, though, people are flying up hills in fifth gear with their tachometer sliding all over and the driver doesn't notice. Some drivers can't even tell that the ESS restart is ready to move the vehicle. Some are stalling because they should recalibrate the throttle pedal but are just popping to 4k to get started and wearing the clutch. The software is here to tell those people to get their inattentiveness to a dealer so someone can pay attention.

ps I don't have a financial interest in Jeep/FCA/Stellantis, not a lawyer, not a dealer.
Or, at lot easier than redesigning the parts so they work properly.

"Do you want them to build a thousand…" Yes. It's called failure analysis, and is standard in most industries, especially where safety is concerned.

"Gosh darn it, these planes just fall out of the sky sometimes for reasons we don't understand, so rather than figure out why engines detonate, we'll just have them spontaneously reduce thrust when we think it might be prudent."

With this same mindset, anything you do in a vehicle could cause injury, so from now on the software just won't allow your vehicle to start if it thinks you're tired or have been accelerating more exuberantly than it thinks is proper. 🙄
 

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Quick update, my ESS started working again. Back to how it was prior to the recall.
Your Jeep was probably just doing the "sixth gear relearn" process. This happens after the battery is disconnected or settings are changed (tire size, gear ratio are examples).
Gregj
 

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Well written. Worth re-posting. As long as FCA follows with a re-designed clutch. At the end that’s the cause of the problem. People not knowing how to drive are driving other manual cars with no issue other than premature wear.
They're going for the band aid solution -- no surprises here typical tactic of most manufuckturers. I wouldn't want that virus in my software . A while back I saw a video ,(not 100% sure if it was a computer control issue but pretty sure it was) where the guy driving a wrangler trough snow could go in reverse but was stuck because it was restricting the throttle to the point the engine didn't make enough power to move it on almost flat ground.
 
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