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-   -   Grenaded clutch (http://www.wranglerforum.com/f274/grenaded-clutch-233660.html)

Elconquistador 04-08-2013 12:04 PM

Grenaded clutch
 
So I went wheeling this weekend at southington offroad in northeast Ohio. The first hill I came down, I grenaded the clutch. I have a 2013 2door rubicon with 3000 miles on it. I was in 4lo and came down off a plateau to a steep hill, and as soon as I hit the descent the clutch just blew apart. Having it towed to the dealership today. Anybody have clutch problems? Think my warranty will cover it?

Jared66 04-08-2013 12:28 PM

How fast where you going. Did you down gear hard or ride the clutch? What gear were you in.

Hokieneer 04-08-2013 12:34 PM

was the clutch pressed in when you started down the hill?

Elconquistador 04-08-2013 12:40 PM

I had the clutch pressed in, but I was in 4lo so the clutch is always engaged. I probably got it up to 4000-4500 rpm before it blew.

Hokieneer 04-08-2013 12:47 PM

sorry I am a bit confused was your foot pressing the clutch pedal in or was your foot off the clutch

Elconquistador 04-08-2013 12:53 PM

My foot had the clutch pressed in down to the floor

Goofyjumper 04-08-2013 12:54 PM

Sounds like you did an over speed on the clutch. If you were going down hill in 4-low and depressed the clutch pedal you could have gotten the clutch disk to spin at an excess of 8,000 rpm. You would not see this on your tachometer as your clutch disk would be spinning from forces imposed by the transmission and not the fly wheel. At that speed your clutch disk would rip apart as it can not handle those speeds.

Ivoryring 04-08-2013 12:56 PM

Quote:

Originally Posted by Elconquistador (Post 3609299)
but I was in 4lo so the clutch is always engaged.

I have never heard that about 4LO... are you sure?

Ivoryring 04-08-2013 01:00 PM

Quote:

Originally Posted by Goofyjumper (Post 3609350)
Sounds like you did an over speed on the clutch. If you were going down hill in 4-low and depressed the clutch pedal you could have gotten the clutch disk to spin at an excess of 8,000 rpm. You would not see this on your tachometer as your clutch disk would be spinning from forces imposed by the transmission and not the fly wheel. At that speed your clutch disk would rip apart as it can not handle those speeds.

What you are saying makes sense - but why would his tach show 4000-4500, unless he has three feet involved....

He said foot depressing clutch fully to the floor, going downhill - so I assume he has a foot on the brake... at which point the engine should be idling, no?

idiot magnet 04-08-2013 01:02 PM

Make sure your jeep is spotless when you take it to the stealership. Much better than a muddy trail driven Jeep. Could save you some headaches with your warranty.
I rarely have my foot on the clutch in 4lo going down hill.

Goofyjumper 04-08-2013 01:06 PM

Quote:

Originally Posted by Ivoryring (Post 3609370)
What you are saying makes sense - but why would his tach show 4000-4500, unless he has three feet involved....

He said foot depressing clutch fully to the floor, going downhill - so I assume he has a foot on the brake... at which point the engine should be idling, no?


I imagine that his initial descent down the hill was with the clutch engaged (pedal up) putting force on the engine (showing tach at 4k) and then the OP pushed in the clutch and that is when the clutch went boom.

8000 rpm equals 133 rotations per second for clutch grenading.

Let's say the tire speed was 2 rotations a second...

2 rotations/second * 4.10 gear ratio * 4 to 1 transfer case ratio * 5 to 1 1st gear ratio === 164 rotations per second or 9,840 rpm (BOOM!)

aypanthony 04-08-2013 01:07 PM

I, too, am curious as to how fast you were going(and gear) when the clutch blew.

So.....When going down a steep decline in 4lo, in this case, it would have been better to ride the brakes to slow the decent? The main issue was speed, correct?

I am trying to understand what happened and how to avoid it.

Elconquistador 04-08-2013 01:11 PM

It defiantly makes sense that I could have over reved the clutch because the guy who towed me back to the campsite was able to pull shreds of clutch fibers out. Hopefully jeeps warranty helps me out! I'll know for later to never ride my clutch...doh

Mike_4462 04-08-2013 01:14 PM

Yep. The flywheel and pressure plate went from 4k to 800 RPM. The clutch disc went from 4k to 9k...BOOM

Elconquistador 04-08-2013 01:14 PM

I had it engaged to get me over the ledge but because the incline was so steep I panicked a little a pressed in the cutch and brake to slow me down and boom no more fun weekend

JEEPDON 04-08-2013 01:16 PM

This is why we keep tranny in gear AND CLUTCH ENGAGED when descending steep grades!! Especially in 4L. The clutch WILL over-speed if allowed to spin freely.

Ivoryring 04-08-2013 01:17 PM

Quote:

Originally Posted by Goofyjumper (Post 3609389)
I imagine that his initial descent down the hill was with the clutch engaged (pedal up) putting force on the engine (showing tach at 4k) and then the OP pushed in the clutch and that is when the clutch went boom.

8000 rpm equals 133 rotations per second for clutch grenading.

Let's say the tire speed was 2 rotations a second...

2 rotations/second * 4.10 gear ratio * 4 to 1 transfer case ratio * 5 to 1 1st gear ratio === 164 rotations per second or 9,840 rpm (BOOM!)

That's making more sense. Sometimes I will catch myself going downhill and realize my feet have gone in muscle memory mode and I've got the clutch depressed fully and my foot on the brake - when I should be just using engine braking instead.

I tend to be a bit of a wimp - I think I've only had my engine near 4k a few times (offroad uphill on wet ice in 4lo, not daring to take the time to shift, but needing to build momentum up). I don't think I'd be anywhere near that rpm going downhill (because I'm a chicken and that sounds like going too fast to be in control to my comfort level) - but it's good to understand how it could happen.

Hokieneer 04-08-2013 01:18 PM

Quote:

Originally Posted by Elconquistador (Post 3609346)
My foot had the clutch pressed in down to the floor

yeah over reved the clutch, that stinks, hopefully no other damage was done

Ivoryring 04-08-2013 01:22 PM

Quote:

Originally Posted by Elconquistador (Post 3609426)
I had it engaged to get me over the ledge but because the incline was so steep I panicked a little a pressed in the cutch and brake to slow me down and boom no more fun weekend

Exactly what I ment by catching myself in muscle memory... good or bad, I've got a "emergency stop" habit from driving other vehicles of "both feet on clutch and brake". It's hard to break those reaction habits.

Hokieneer 04-08-2013 01:26 PM

Quote:

Originally Posted by Ivoryring (Post 3609442)
That's making more sense. Sometimes I will catch myself going downhill and realize my feet have gone in muscle memory mode and I've got the clutch depressed fully and my foot on the brake - when I should be just using engine braking instead.

I tend to be a bit of a wimp - I think I've only had my engine near 4k a few times (offroad uphill on wet ice in 4lo, not daring to take the time to shift, but needing to build momentum up). I don't think I'd be anywhere near that rpm going downhill (because I'm a chicken and that sounds like going too fast to be in control to my comfort level) - but it's good to understand how it could happen.

I think that rpm was coming down the hill was more for getting enough resistance to go slowly down hill not really giving it gas, at 4.5k rpm in a rubi in 1st in 4 low is 3-4 mph. Its one big thing to get used to coming from a 4.0L to the 3.6 the 4.0l would stay really low on hill descents rarely over 3k but the 3.6 is pretty rev happy so I wouldn't worry about 4.5k should hurt anything

JEEPDON 04-08-2013 01:27 PM

Quote:

Originally Posted by aypanthony (Post 3609395)
I, too, am curious as to how fast you were going(and gear) when the clutch blew.

So.....When going down a steep decline in 4lo, in this case, it would have been better to ride the brakes to slow the decent? The main issue was speed, correct?

I am trying to understand what happened and how to avoid it.

The main issue was not speed, but descending a hill with the clutch depressed while in 4L. THAT is a no-no.
Personally, I never press clutch while descending a hill- even in 4H or 2H; except to shift or stop. When stopping, I keep clutch engaged until almost stopped, THEN step on the clutch pedal.
Put tranny in first gear and TC in 4L, and let the engine hold you back.
This is one reason that I believe that all stock JEEPS put way too tall of gears in their diffs.
I am running 5.38's with a 4:1 TC. First gear in 4L gives me like a 94:1 crawl ratio. I never need to ride the brakes going down steep grades!
PS. As a side note. I don't know how drivers test examiners are today with manual transmissions; but when I took my test (circa 1960), they would fail you for stepping on the clutch too soon coming to a stop sign or going down a hill. Yeah, I am an old fart!!
And having spent a lot of years in the big rigs, there you also want to keep the clutch engaged at all times. And I do know the CDL examiners will fail you for the above stated reasons if you are testing to get a CDL.

clayps 04-08-2013 01:33 PM

So pressing in the clutch and letting the vehicle just coast down hill while foot on the brake is a no no in 4lo? You're better off keeping the clutch engaged and vehicle in gear and just riding the brake at that point? It makes sense to me, but like Ivoryring states its all muscle memory and I'd likely forget that 4lo has a very low stall point and would be afraid to use my brakes.

I'm new to the Jeep as well as 4wd. What gears can be used in 4lo? I'm assuming anything past 2nd gear wouldn't really help much..

In the OP's case..what gear would have been the best for his situation?

JEEPDON 04-08-2013 01:45 PM

Quote:

Originally Posted by clayps (Post 3609497)
So pressing in the clutch and letting the vehicle just coast down hill while foot on the brake is a no no in 4lo? You're better off keeping the clutch engaged and vehicle in gear and just riding the brake at that point? It makes sense to me, but like Ivoryring states its all muscle memory and I'd likely forget that 4lo has a very low stall point and would be afraid to use my brakes.

I'm new to the Jeep as well as 4wd. What gears can be used in 4lo? I'm assuming anything past 2nd gear wouldn't really help much..

In the OP's case..what gear would have been the best for his situation?

If you guys and gals new to wheeling are relying on "muscle memory " rather than thought process......maybe you need to proceed a little slower, take a little more time, and think about what you are going to do.
I know, some of the places we put our JEEPS can be more than just a little nerve racking. This is where going with someone that has a LOT of experience off road in the technical stuff can really be a huge help.

Hokieneer 04-08-2013 01:50 PM

here is a pretty good article on it

Exploding Clutch - Tech Tip

What gear you are using in 4L just depends on what your doing

Elconquistador 04-08-2013 01:58 PM

Great article! Thanks, that is pretty much exactly what happened. We learn from our mistakes though, this just happens to be an expensive one haha

JEEPDON 04-08-2013 02:04 PM

Quote:

Originally Posted by Hokieneer (Post 3609579)
here is a pretty good article on it

Exploding Clutch - Tech Tip

What gear you are using in 4L just depends on what your doing

Sounds just about like I was talking to myself in that article!!!!:thumb::thumb:

Ask me how I know to keep clutch engaged while wheeling!!! Only I did it in reverse!

Jared66 04-08-2013 02:06 PM

Never depress your clutch and coast down hill. Gear down and run in gear. 1. Ita illegal to coast down a hill and 2. You cause damage like blowing yor clutch and wearing your breaks. Use your gears. That's what there there for.

Ivoryring 04-08-2013 02:06 PM

Quote:

Originally Posted by JEEPDON (Post 3609562)
If you guys and gals new to wheeling are relying on "muscle memory " rather than thought process......maybe you need to proceed a little slower, take a little more time, and think about what you are going to do.
I know, some of the places we put our JEEPS can be more than just a little nerve racking. This is where going with someone that has a LOT of experience off road in the technical stuff can really be a huge help.

In my case it isn't a matter of relying on muscle memory so much as "focus on one thing, and if things start to get a little out of control, the muscle memory kicks in". And that is exactly why I said I'm a chicken and a wimp... when possible, I prefer to take it slower. I did some off road driving this winter on ice, and won't be repeating that.

I also do as you mention and go with a group of much more experienced guys. Ultimately though, we all learn through making mistakes... I'm pretty sure the OP won't be repeating this one (no matter who pays for the replacement clutch).

legitposter 04-08-2013 02:16 PM

The moral of this story: Don't take your wrangler off road.

live_slow 04-08-2013 02:18 PM

I remember the first "group ride" I did as an adult. Before the long decent, members of the Jeep club familiar with the trail stood about 15 yards before it and talked to every driver, spending a while with the MT people to remind them of what was about to happen. (And also reminding them to "follow through" the decent and not congregate at the bottom to congratulate each other)


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