Max RPM When Engine Braking?

flyer92

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Soooo...although I've owned several Jeeps over the years, I have never lived in a hilly or mountainous region until I got my 2-door JL with 3.6L. Today, my brother-in-law was demonstrating some engine braking techniques on a very steep mountain road, and we spent at least 2-3 minutes at 4500 rpm in second gear. Third gear just didn't slow our descent effectively, and the 3.6L engine red lines at 7000 rpm. However, I still thought 4500 rpm was a bit excessive, and am a little concerned about engine damage at that gear/speed. Still new to the Pentastar, so just curious what you all think, and if you have any experience, advice to share. Many thanks!





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flyer92

flyer92

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After re-re-reading the owner's manual, I remembered that the AutoStick feature will revert the trans to automatic mode if it senses an abnormal overspeed or overtemp condition, so I think I might be OK....but you never know. Still curious what others do or have observed while engine braking downhill, especially with regard to rpm's in lower gears.
 

JeepinPete

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Wouldn't worry in the slightest at 4500 rpm. I would run it up to 6k for a short duration if necessary.

Pete
 

garyji

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No Problem at all. Used effectively, you'll be amazed at your new brakes life. Been using it for years on all vehicles. Got 80K+ on the front disks on my 2016 Tacoma.

G.

G.
 

JJMalone

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No Problem at all. Used effectively, you'll be amazed at your new brakes life. Been using it for years on all vehicles. Got 80K+ on the front disks on my 2016 Tacoma.

G.

G.
^This. My Tacoma has 110K on it. Rear brakes replaced because of an axle seal leak. Front discs are original and about 50%. '20 JLR 3.6 auto at 77,000 miles, brakes are about 80%. I use engine breaking all the time and use the highest gear that yields the braking necessary.
 

garyji

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Got 100k on the fronts of my 2006 Taco. (Rears are still drums)

G. ;)
 
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flyer92

flyer92

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Thanks, all...I sort of figured 4500 rpm was OK based on the 7000 rpm redline, but just wasn't 100% comfortable with all the noise coming from my engine. Guess it just sounds worse than it really is, so really appreciate all the feedback.

Per the manual's discussion about AutoStick referenced above, I now wonder at what maximum rpm the system reverts back to automatic shifting. I don't think I want to try it out for myself, but just curious if anyone has experienced this, as it would be a good threshold to keep in mind when engine braking.
 

garyji

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Jeff,
Don't over-think it. The computer will take care of it. It works just fine. For instance, if you are doing "manual mode" and come to a stop in 3rd gear, it knows to shift you back to 1st to get going again. It's really smart.

G.
 
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flyer92

flyer92

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Jeff,
Don't over-think it. The computer will take care of it. It works just fine. For instance, if you are doing "manual mode" and come to a stop in 3rd gear, it knows to shift you back to 1st to get going again. It's really smart.

G.
LOL...thanks Gary, you are 100% correct. After decades of driving a completely non-automated, non-cushy, non-infotainment-having CJ-5, it's just a bit difficult getting used to all the electronic voodoo! Appreciate the support though...exactly why I love this great forum.
 

DaltonGang

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I was engine braking in mine, going down Pikes Peak, and had to use the regular brakes to assist the engine braking. The rpms were really climbing.
 

omnitonic

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It really doesn't matter to the pistons and valve train whether they are driving the wheels or being driven by them. My personal rev limit is about 90% of the redline on pretty much any engine. That's as high as I will go either accelerating or engine braking, and I usually keep it below maybe 75%. Call it 5,000 on the Pentastar. I would be totally comfortable revving that high for 30 straight miles going off a mountain.

I use engine braking all the time. It's less about trying to save wear on the brakes and more about keeping the brakes nice and cool. I have experienced brake fade. I actually experienced a tire fire caused by a glowing brake drum. That was like 25 years ago. I only had to live through that shit once to start taking engine braking VERY seriously.

My 2013 F150 has 115,000 on the odometer, and still has all the original factory brake parts. I do pretty good keepin'em cool. 😎
 

omnitonic

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"Tuten did a bit of napkin math and figured that at 55 mph, the engine was spinning somewhere around 50,000 rpm, well above the factory redline of 6,600 rpm." Wow!

I suppose I should add the addendum that while it doesn't matter what's making things turn, they are only designed to turn so fast before going kaboom. That article is an excellent example of a kaboom.
 

omnitonic

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That article is an excellent example of a kaboom.
I thought about that some more. It was in 1st gear, in 4 low. What the hell kind of RV was that guy using to pull that thing? The engine braking effect would have been massive.
 

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