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Old 12-29-2016, 12:46 PM
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Help me understand - manual tranny

Hey everyone, I'm sure this is a noob question, but, I'm gunna ask anyway.

I've read a lot recently about how shifting a manual in deep water is bad, because you can get mud and crap in your transmission. What I don't understand is how can that happen? If the manual trannies are sealed to the point of not necessarily needing a fluid change, how does water/mud find its way into one as a matter of general rule?

I've looked up vents, but can only find breather tube references for the axles and auto trans.

Is the problem with the GIANT HOLE in the bottom of the tranny that I'm pretty sure I can feel the flywheel thru? If that's the case, how does road grime not get in there to ruin things driving thru puddles and dirt roads?

If this gaping hole is the problem, why is it on the bottom to begin with? Can I put a strong piece of duct tape over it for temp protection if possibly deep water is anticipated?

If that hole is not the problem, please enlighten me, with pictures if you can, because I really don't understand =\

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Old 12-29-2016, 12:58 PM   #2
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This thread might answer your questions..

https://www.wranglerforum.com/f274/wa...on-107556.html

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Old 12-29-2016, 01:40 PM   #3
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The problem isn't so much the transmission as it is the clutch. With the clutch disc engaged to the flywheel there is typically no debris there between the clutch disc/flywheel/pressure plate. As you disengage the clutch to change gears, because the surfaces are no longer mated to eachother. You introduce a gap between them that allows debris to get in. Then when you engage again, all this debris can allow slipping as the disc slips and grinds this debris across the flywheel. If its hard to visualize..hold your hand against the table with a lot of force and try and slide it across the table. It takes a lot of force to move your hand (clutch disc pressed to flywheel). Now imagine putting dirt under your hand and trying the same thing. Your hand will slide, and you will scratch both your hand and the table. It can potentially cause damage. If it's clear water, not so bad.. that water will dry up. However dirty water, or even worse mud. Not so good...
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Old 12-29-2016, 01:44 PM
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So I saw that previous thread, and that and the post from czar, I understand what the problem is with it, dirt and stuff in between the clutch parts, what I don't understand is how it gets there?

I will reread that thread tho to see if I overlooked anything.
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Old 12-29-2016, 01:47 PM   #5
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Simply, like a lot of things, just use your best judgement. Grit and sand will hurt your clutch. I do not know if throwing some duct tape on would help or hurt as it needs to drain water out if it gets in.

Your best bet is to try to not shift, start in a comfortable gear in 4 low. The link that talks about floating gears doesn't mention floating gears in 4lo is easier said than done. Shifting with a clutch in 4lo is often clunky and difficult, floating gears with the resistance pushing again you in water is a no go in my mind, you would come to a stop before you grabbed the next gear!

Just be smart. If you have to shift... then shift. If you can help it don't. I often downshift in water, because I rarely need more speed. But I am not in deep deep water.
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Old 12-29-2016, 01:50 PM   #6
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So I saw that previous thread, and that and the post from czar, I understand what the problem is with it, dirt and stuff in between the clutch parts, what I don't understand is how it gets there?

I will reread that thread tho to see if I overlooked anything.
The clutch is not water tight. I has vents. So when you push the clutch and pull the pressure plate away from the flywheel dirt can get in between. Most dirt will work its way out and is not a problem.
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Old 12-29-2016, 02:18 PM   #7
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So I saw that previous thread, and that and the post from czar, I understand what the problem is with it, dirt and stuff in between the clutch parts, what I don't understand is how it gets there?

I will reread that thread tho to see if I overlooked anything.
The clutch, pressure plate, flywheel, and throw out bearing/fork are not inside the transmission. I think that's where your misunderstanding is. They are between the engine and transmission in a bellhousing. That bellhousing has two big ventholes at the bottom that let junk in and out.

This is the simplest diagram I could find
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Old 12-29-2016, 03:02 PM   #8
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I always think this subject gets a little over blown. We've been playing in the water and mud long before automatic transmissions hit the scene in 4x4's. I'm not saying don't use common sense but at the same time don't sweat it.
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Old 12-29-2016, 04:39 PM   #9
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I always think this subject gets a little over blown. We've been playing in the water and mud long before automatic transmissions hit the scene in 4x4's. I'm not saying don't use common sense but at the same time don't sweat it.
Totally agree with you here. I have never had an automatic off road capable vehicle. If you are in water deep enough to damage your clutch, something else is going to be a problem way before you destroy your clutch from shifting.
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Old 12-29-2016, 05:39 PM
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Blastek, that clears a lot up. I didn't know that the bell housing was even a separate thing, I thought it was just part of the transmission.

So then my next question, is the vents for the bell housing, what is their purpose? Since it's not for fluid pressure expansion. And whose bright idea was it to expose such vital components to the elements?
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Old 12-29-2016, 06:31 PM   #11
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I'm not sure why it isn't sealed but I can assure you it can be bad in deep mud. A buddy of mine buried his jeep in a deep mud hole and pressed and held down the clutch while we hooked up to pull him out. With the clutch down the fingers on the pressure plate are spread apart. When he released the clutch mud/sticks/debris had gotten all in between these fingers. So the clutch wouldn't make contact with the flywheel even when the clutch was pulled up. Had to pull him off the trail and all the way home. Then had to pull the clutch and spray out the pressure plate fingers with a pressure washer to clear it. Was a huge mess.
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Old 12-30-2016, 06:35 PM   #12
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I was taught not to shift when fording. Engage all wheel drive and put it in 1st , keep rpm's up , slow and steady , start up stream from where you want to come out.
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Old 12-31-2016, 03:36 PM   #13
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I always think this subject gets a little over blown. We've been playing in the water and mud long before automatic transmissions hit the scene in 4x4's. I'm not saying don't use common sense but at the same time don't sweat it.
Agree'd. The clutch disk has grooves to force crap out, not like it's a solid surface. I've had 2 different Cherokee's in deep water (several times with water spurting up through the transmission hump, once sitting waist deep while in the drivers seat and on another occasion needing to climb out the window because mud/earth/water would not allow the door to open), all needed to be run first to reverse... neither vehicle failed, several times in clear water, once in nasty in brown water the other already described.
It's hard to agrue the theory of all the nay-sayers because it's sound theory, however my experience has shown otherwise.
If it were the case, the same would hold true for brakes. They too clamp a surface.
Cannot speak to running/being buried in landslide material or quicksand, but could see how in those circumstances the theory may well hold true.

Having said all that, I avoid shifting in those circumstances if at all possible due to lost momentum, not for fear of destroying the clutch.
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Old 12-31-2016, 03:40 PM   #14
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one more thing... go watch some ancient footage of Camel Trophy...
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Old 01-02-2017, 06:17 PM   #15
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With manual transmission's ones experience will determine the gear you need to stay in. I often have to cross streams/mud pits in the spring, the best practice for me is 4low and 2nd gear and go smooth through the hazard to prevent needing to grabbing another gear. Rather similar in climbing or decending a very steep grade.
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Old 01-02-2017, 07:25 PM   #16
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As stated before, it is a bit overblown. Fording deep water can destroy your transmission in the same way it can hydrolock your motor, or get into your diffs, or flood your transfer case. THERE IS NEVER ANY GUARANTEE THAT YOUR POWERTRAIN CAN SURVIVE DEEP MUD OR WATER. There is always a chance it will get in, and manage to ruin something.

As far as the "What gear should I be in" depends on you, the obstacle itself, and your rig. 2nd gear on my Rubi has the same amount of final gear reduction as 1st gear in a Sport/Sahara.

Take your rig off road, put it in 4lo. You'll figure out the feel for the gears within the first 15 minutes. It will become painfully obvious very quickly what gear you want to be in for what purpose. My advice would be if you are still not comfortable fording water or a deep mud, avoid it until you are.

Trust me when I say you're overthinking it! Go off road with some friends, take part in a local Jeep group! You will have a blast, don't be afraid!
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Old 01-02-2017, 09:18 PM   #17
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Directed to the technical aspects... I believe the holes are there due to the dry nature of the clutch. It has no fluid to cool it so it needs to let the air in the space expand and contract... and likely a form of clutch-dust removal as well.

More to the point, here is what the holes look like on the JK It's the Big Hero 6 looking slot just aft of the oil pan....


I have pondered that it must be reasonable for anyone truly concerned enough to plug the holes, temporarily while fording. The shape makes it tricky, but a urethane plug could be cast pretty easily.

The fact that I am unaware of anyone doing this before, suggests all the advice above is correct, and to not worry too much.
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Old 01-03-2017, 05:34 PM   #18
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Also I would guess that is not the only plug needed. I would guess there is a place on the side for a barring tool to move the flywheel... Just a guess tho, I have never looked.
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Old 01-04-2017, 04:20 PM   #19
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So then my next question, is the vents for the bell housing, what is their purpose? Since it's not for fluid pressure expansion. And whose bright idea was it to expose such vital components to the elements?
From what I've read, it's either an inspection port (i was told by the dealer that they cannot inspect the clutch from the port), a vent to cool the clutch, or a port to let clutch dust out. My other two 5 speeds (01 escape/ 96 200sx) do not have a vent on the bellhousing like the JK's. They're completely sealed and have a vent tube from the transmission side, which is normal.

You could block it and drill a hole on the top side, but I would just avoid shifting in water. You can restart the jeep without the clutch if it stalls in 4low. I can say this, it won't take you long to search and find many examples of ruined clutches or throwout bearings due to shifting in mud.
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Old 01-04-2017, 05:17 PM   #20
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So then my next question, is the vents for the bell housing, what is their purpose? Since it's not for fluid pressure expansion. And whose bright idea was it to expose such vital components to the elements?
From what I've read, it's either an inspection port (i was told by the dealer that they cannot inspect the clutch from the port), a vent to cool the clutch, or a port to let clutch dust out. My other two 5 speeds (01 escape/ 96 200sx) do not have a vent on the bellhousing like the JK's. They're completely sealed and have a vent tube from the transmission side, which is normal.

You could block it and drill a hole on the top side, but I would just avoid shifting in water. You can restart the jeep without the clutch if it stalls in 4low. I can say this, it won't take you long to search and find many examples of ruined clutches or throwout bearings due to shifting in mud.
I'd leave it alone and as stated above just avoid shifting in the water.

I will also say plugging the bottom and adding a hole topside is a terrible idea. Should water or mud be forded taller than the transmission, any debris or water that enter the bell housing will be thoroughly trapped. If your "sealing" fails, same thing.

I bet for every manual transmission failure caused by shifting water or mud, there is an equal if not greater amount of hydrolock threads, or pictures of milky dirty diff oil, shorting out electrical connectors or ruined sensors, etc etc. People don't buy "Flood" cars for this very reason.

Bottom line is fording water or deep mud has a very high probability of damaging something. It's up to you if you wanna take the risk.
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Old 01-04-2017, 09:23 PM
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I guess I just didn't think that it would need a vent to cool it, but I supposed it makes sense for that reason. I'm not thinking of intentionally planning on shifting in water if the situations arises. However, if I get to a point that I no longer feel comfortable with going forward, and I want to stop, and back up, I will have to shift. Just trying to understand more where the problem originates from, after having read many times what the problem is.

Guess my next step in that situation is to see if you can start in reverse in 4lo without the clutch in, haha
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Old 01-04-2017, 11:07 PM   #22
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I guess I just didn't think that it would need a vent to cool it, but I supposed it makes sense for that reason. I'm not thinking of intentionally planning on shifting in water if the situations arises. However, if I get to a point that I no longer feel comfortable with going forward, and I want to stop, and back up, I will have to shift. Just trying to understand more where the problem originates from, after having read many times what the problem is.

Guess my next step in that situation is to see if you can start in reverse in 4lo without the clutch in, haha
Yes you can start in 4lo without depressing the clutch. I use that feature when I sleep in the back!
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Old 01-05-2017, 09:26 PM
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Yes you can start in 4lo without depressing the clutch. I use that feature when I sleep in the back!
Yeah, tested it before I left for work today. What does sleepign in the jeep have to do with using the clutch to start it?

btw, I had read that you could start it in 1st 4/lo, but didn't see anything mentioned about reverse. I guess you learn something new every day
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Old 01-05-2017, 11:07 PM   #24
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Yeah, tested it before I left for work today. What does sleepign in the jeep have to do with using the clutch to start it?

btw, I had read that you could start it in 1st 4/lo, but didn't see anything mentioned about reverse. I guess you learn something new every day
So I can just turn the key from the back without getting out of the sleeping bag... In neutral of course!

Edit: what gear it is in doesn't matter, just harder on the starter. So wouldn't think reverse would be any different. But never tried it.

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