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I smoked my clutch today

omnitonic

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After watching some Youtube videos of guys walking right up and on top of tree stumps and big rocks, I realized that is a thing a Jeep can do. I'm new to this game. I'm learning what I can pull off.

There is a parking lot in my neighborhood with a stupid high curb that has destroyed many air dams on many FWD cars. It's pretty stupid for cars, but it seems like a great place to practice rock crawling skills. It's about 20" tall, and it's at about an 88° angle. I have the clearance to go up the curb and over the sidewalk, but I've found that it's actually very hard to do in practice.

I have JLU Willys with stock 32" Firestone Destination MT/2s and the 6MT. In order to avoid stalling on a hill, I have to rev it fairly high, and ease through the clutch release to avoid stalling. My usual driving around a hilly town technique wasn't nearly in the ballpark to get over this obstacle. I bumped into it, bounced off. I stalled out a couple times.

I finally made it over in 4 low, but I was revving to nearly 5,000 to get there, and as I started to go up and over, I saw a huge cloud of smoke. Shit! That was clutch! I am really ashamed of how badly I smoked the clutch. I've driven manual transmissions for decades, mostly in 18-wheelers, and smoking a clutch is BAD BAD BAD BAD BAD m'kay?

So I thought I would ask for advice on what I did wrong. One thing I can think of is that if I had aired down, it would have helped. I obviously wasn't going to air down pulling a silly stunt in a commercial parking lot before climbing a sidewalk onto a paved street, on my way to Harbor Freight to buy trim removal tools for my upcoming Mopar aux switch install.

Maybe I should try this exercise aired down though. This 20" obstacle isn't jack compared to stuff I've seen people clear in these things, but it's a really tall challenge to me. This seems like a good opportunity to get some rock crawling practice in, and if I'm going to destroy a clutch, it's better that it be a clutch that is still under warranty.

Still, I hate smoking a clutch. I know the arguments for automatics on crawls, and torque converters actually do this job better. Even so, people have been rock crawling since the original Willys MB, and I know it can be done. Obviously, my technique is just complete shit, and I need some training.
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This seems like a good opportunity to get some rock crawling practice in, and if I'm going to destroy a clutch, it's better that it be a clutch that is still under warranty.
You sure about that? I thought clutches, like brakes and tires, were consumable/wear items and not covered by warranty.
 

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You sure about that? I thought clutches, like brakes and tires, were consumable/wear items and not covered by warranty.
The clutch and brakes are covered for 1 year/12,000 miles. Tires have whatever warranty the tires normally come with.
 
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Some Random Guy

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Better to learn this on a trail. Be in 4L, and you should be able to just ease the clutch out with no gas and crawl up things. I can’t remember if you have the rubicon t-case, but if you don’t a 20” obstacle should be ok. If you actually manage to stall, you have to go old school and bring the engine up to 1500 rpm with the clutch fully in and hold the skinny pedal in that POSITION (not that RPM) while you work the clutch to climb (with more room before you stall now that you’re letting the engine breathe more than idle). Easier said than done, especially if you’re trying to step through something and have to keep stopping.
 

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After watching some Youtube videos of guys walking right up and on top of tree stumps and big rocks, I realized that is a thing a Jeep can do. I'm new to this game. I'm learning what I can pull off.

There is a parking lot in my neighborhood with a stupid high curb that has destroyed many air dams on many FWD cars. It's pretty stupid for cars, but it seems like a great place to practice rock crawling skills. It's about 20" tall, and it's at about an 88° angle. I have the clearance to go up the curb and over the sidewalk, but I've found that it's actually very hard to do in practice.

I have JLU Willys with stock 32" Firestone Destination MT/2s and the 6MT. In order to avoid stalling on a hill, I have to rev it fairly high, and ease through the clutch release to avoid stalling. My usual driving around a hilly town technique wasn't nearly in the ballpark to get over this obstacle. I bumped into it, bounced off. I stalled out a couple times.

I finally made it over in 4 low, but I was revving to nearly 5,000 to get there, and as I started to go up and over, I saw a huge cloud of smoke. Shit! That was clutch! I am really ashamed of how badly I smoked the clutch. I've driven manual transmissions for decades, mostly in 18-wheelers, and smoking a clutch is BAD BAD BAD BAD BAD m'kay?

So I thought I would ask for advice on what I did wrong. One thing I can think of is that if I had aired down, it would have helped. I obviously wasn't going to air down pulling a silly stunt in a commercial parking lot before climbing a sidewalk onto a paved street, on my way to Harbor Freight to buy trim removal tools for my upcoming Mopar aux switch install.

Maybe I should try this exercise aired down though. This 20" obstacle isn't jack compared to stuff I've seen people clear in these things, but it's a really tall challenge to me. This seems like a good opportunity to get some rock crawling practice in, and if I'm going to destroy a clutch, it's better that it be a clutch that is still under warranty.

Still, I hate smoking a clutch. I know the arguments for automatics on crawls, and torque converters actually do this job better. Even so, people have been rock crawling since the original Willys MB, and I know it can be done. Obviously, my technique is just complete shit, and I need some training.
Next time you see a large rock or stump etc... Put the jeep in 4 wheel low and 1st gear. Release the clutch and let the jeep try to climb the obstacle. (do not push in the clutch, unless you need to stop at the top, or hit the gas) See if the jeep can make it up without stalling. Unfortunately, your crawl ratio stock is 52:1 in a non-rubi. The higher the number the easier it will be to get over large obstacles without any input. You can either increase it by swapping in a rubicon transfer case, atlas (if they make one at some point), or change the ratio in the axles.

My TJ has a crawl ratio of 98:1 and no joke will keep trying to move forward to the point of breaking traction on the tires even if I point it at a vertical wall. Prior to my atlas I had an np231 and a crawl ratio around 53:1. While I did trails such as the rubicon with the np231 the 5:1 in the atlas made life much more enjoyable because of the increased control you get with the slower pace.

Crawl ratio is: 1st gear ratio x transfer case ratio x axle ratio

A rubicon Stock is: 5.13x4x4.10=84.13
Non Rubicon: 5.13x2.73x3.73=52
(manual)

Example - Regear to 4.88: 5.13x2.73x4.88=68

Check out grimm jeeper and check out the charts. They are very helpful to determine how much gearing will affect your highway / off-highway performance.


If you want to get into rock crawling I'd highly recommend you have the axles regeared or look into a transfer case swap in the future.
 
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omnitonic

omnitonic

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Better to learn this on a trail. Be in 4L, and you should be able to just ease the clutch out with no gas and crawl up things.
I would prefer to be on a trail, but the only rock crawling trail I know about in this area is one I have been warned to avoid until I've done a lot more upgrades.

I approached the curb in gear in 4L and just ricocheted off of it. To get up and over, I had to stop, plant the tires on it, and really force my way through. My desire to drive over the thing overcame any common sense I might have brought to the problem. :CWL:

I can’t remember if you have the rubicon t-case
I do not.

If you actually manage to stall, you have to go old school and bring the engine up to 1500 rpm with the clutch fully in and hold the skinny pedal in that POSITION (not that RPM) while you work the clutch to climb (with more room before you stall now that you’re letting the engine breathe more than idle). Easier said than done, especially if you’re trying to step through something and have to keep stopping.
After reading through that a few times, I think the main thing I need to work on next time is setting a target RPM with the gas pedal, and leaving it there. I think as I started to feel a stall coming on, I gave it more and more gas, as I do when pulling out on the street. I probably panicked a little, too.
 

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After reading through that a few times, I think the main thing I need to work on next time is setting a target RPM with the gas pedal, and leaving it there. I think as I started to feel a stall coming on, I gave it more and more gas, as I do when pulling out on the street. I probably panicked a little, too.
Yes, target throttle position, not RPM. If you stall, start again and target a few hundred RPM higher start point. Think of it as a carb or throttle body, you want to control the air available to the engine, not the RPM. That buys you more room to load the engine before it stalls.
I abused my clutch the first few times in 4L because nobody explained this to me.
 
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omnitonic

omnitonic

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If you want to get into rock crawling I'd highly recommend you have the axles regeared or look into a transfer case swap in the future.
Okay, that's a very, very fair point. Just because I saw a bunch of built Rubicons do this on Youtube does not change the laws of physics. I might be able to improve my technique and do less harm, but the real key here is that basically every ratio on this thing is stacked against me right now.

I've already spent a lot of time playing with the Grimm Jeeper calculator, and none of the options I'm currently considering for gears and tires will do much to improve my crawl ratio. I'm sure if I start punching in lower final drive ratios, I'm going to find the engine screaming too much on the highway to suit me, so this means if I want a good rock crawler, I need to throw a transfer case onto the list of necessary upgrades.

The good news here is that I only know of one place to go rock crawling around here, and it's going to involve way worse than my silly little curb. I already concluded I'm not tackling that particular trail until I perform at least $10,000 in upgrades, and I simply don't have the budget. I guess it's more like $15,000 in upgrades now.

Well, that's part of the learning curve, I guess. Monkey see, monkey do, but the monkey should look at what the other monkey is actually running before trying to copy the stunt. I will let the memory of my clutch smoke serve as my reminder that I should just leave that curb alone. It's not like I actually NEED to drive like a complete asshole anyway. It's just fun. 😁
 
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Yes, target throttle position, not RPM. If you stall, start again and target a few hundred RPM higher start point. Think of it as a carb or throttle body, you want to control the air available to the engine, not the RPM. That buys you more room to load the engine before it stalls.
I abused my clutch the first few times in 4L because nobody explained this to me.
I will adopt that way of thinking about the problem. It does make sense.
 

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I will let the memory of my clutch smoke serve as my reminder that I should just leave that curb alone. It's not like I actually NEED to drive like a complete asshole anyway. It's just fun. 😁
Just stack some rocks and make the approach not as steep. - Don't forget to remove the rocks before taking the photo ;)
 

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Air down the tires...I know you said that feels dumb for this one obstacle, but it does more than just give you more traction. It will help you transition UP the rock/curb with the front tires. Think of it this way, when you are aired down, say 15 psi, and sitting flat on the parking lot you squish the tires down and increase the contact patch. As you air down, you can see your axle or body get closer to the ground. Well, as you approach the curb, the Jeep will push into the curb. That force on the front of the tires will squish the tires in, this pushes air to the bottom of the tire and will actually "lift" the front up. If you could graph the hub in the front, x vs y. You'd see a much smoother curve or transition from x to y or distance to height.

-sorry for the dry explanation...but I did you "squish" twice... LOL

My two cents...
 
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omnitonic

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Air down the tires...I know you said that feels dumb for this one obstacle, but it does more than just give you more traction. It will help you transition UP the rock/curb with the front tires.
I definitely agree airing down would help a lot. It's just not worth the time for this one obstacle that I really have no real need to drive over in the first place. Maybe one day when I just want to fart around going over that again and again.

This thread has really made me pause to consider how poorly equipped I am for rock crawling anyway. Really, that isn't such a terrible thing. If I felt like it was more in reach, I'd be tempted to start down a slippery slope. Since I know it's just not in reach at all, I'll just focus on being happy with what my Jeep does well, which is plenty.
 

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So I thought I would ask for advice on what I did wrong.
You're supposed to drive around stuff like that... Rock climbing tears up the hardware. Leave that to those with the bottomless pockets and/or no brains.
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