Manual Trans - RPM oddity?

Terpsred

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anyone notice that when you lift off throttle the RPMs stay elevated a bit? I've noticed that my 2021 does not drop to idle when off the throttle and clutch depressed or in neutral while rolling.

I'll watch a bit more, but it seems a bit speed sensitive. RPMs will stay 2500-3000 coasting to a stop, then drop to idle once stationary.

Anyone else notice this?
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GreySportySpice

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Yup. The manual has very bizarre characteristics. This is one that I have no idea why it does it or even if it is supposed to.
 

AcesandEights

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Called rev hang. Most (from what I read) car manufacturers have this with manual transmissions. It's an emissions thing, believe it or not.
 

Maverick909

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This is for helping make shifting smoother from what i have found. its like this across the board with manual transmissions
 

m3reno

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Rev-hang. All manufactures have incorporated this into their vehicles. It's supposed to burn off the additional unburned fuel in between shifts which in turn will drop the NOx gasses emitted from your vehicle. I hate it ! But on my last visit to the dealership they did a TSB that was meant for my clutch issues but it seemed to also help the rev-hang. There is a company on this forum trying to come up with a tune to try and eliminate it.
 

OldGuyNewJeep

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anyone notice that when you lift off throttle the RPMs stay elevated a bit? I've noticed that my 2021 does not drop to idle when off the throttle and clutch depressed or in neutral while rolling.

I'll watch a bit more, but it seems a bit speed sensitive. RPMs will stay 2500-3000 coasting to a stop, then drop to idle once stationary.

Anyone else notice this?
Rev hang. Only happens if you shift late, like 5k rpm. Shift earlier if it bothers you.

Tons of great YouTube videos on what rev hang is and why it is.

https://www.jlwranglerforums.com/forum/threads/6-spd-mt-hanging-onto-revs.57066/
 

Minilla

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So I've noticed that my 2021 since I did the dealer computer update recall the rev hang is only there if I give it gas while the clutch pedal is pressed in or give it gas while the pedal is let out.

If I get up to 3-4k rpms then let off completely from Gass and press the clutch pedal the revs drop immediately to around 2k rpms by the time I let the clutch pedal back out.

It used to sit at 3-4k rpms making for a very uncomfortable shifting experience.

So I'd check for updates at ur dealer
 

AMKRubicon610

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Yeah I hate that it does it, it’s especially there when the engine is cold. It’s so freaking embarrassing lol especially if you have a louder exhaust
 

58Willys

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The emissions aspect of this makes sense, even though I hate it. Also odd is if you try to down shift without the clutch, you can’t rev match because the throttle is non responsive. If I down shift with the clutch I can match rev’s. Computerized vehicles drive me nuts sometimes. Then again they a lot easier to start on a cold morning compared to carb/choke‘d motors.
 

Kreepin1

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I have to say the drive-by-wire throttle is the worst thing about my JL. Oddly, I don't have any of these issues with my 2012 JLR which is also a 3.6 w/manual transmission.

As I understand it, rev hang is when you upshift but the engine rpm's don't drop to match the new gear. This is done for emissions reasons on port injected engines. I have the Livernois tune and they have pretty much eliminated this. When I shift rpm's start dropping immediately (but not as fast as other vehicles I've owned).

Two other annoying artifacts of drive-by-wire and emissions remain after the Livernois tune. When the engine is cold and you coast in neutral the engine will race to 3,000 rpm of so as described above. Second, when cruising just off idle like in a parking lot or (especially) in low range heading down a trail the fuel will cut off every 3-4 seconds like clockwork. This last one is super annoying as it happens even after the engine warms up and makes it impossible to drive smoothly under these conditions.
 
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