My current job is driving railroad crews to where they need to go, and half of the places I need to get them to is offroad and poorly maintained (if maintained at all). I drive the company's 2006 Chevy Suburban with 4WD.

This is a high-rainfall area, and sometimes I have to go through deep water. I am okay with this as long as I have some idea what I'm doing. I know to go very slowly.

My question: how deep can I go safely? If I had a crew member hanging out the front window to visually check the depth, how deep is where we're getting too deep? To the bottom of the doors? Or is that pushing it?

Also, there seems to be Upper and Lower 4WD buttons. I've used the upper one when I've need to, but never the lower one. What is the difference?

Any info and tips welcome.

Sue

The difference between 4WD high and low is a gearing ratio, usually. If you put it into low, the vehicle will go slower for a given level of engine revolutions, and that's a pretty basic explantion. It allows the vehicle to have more torque to run at lower speeds.

My guess is that the absolute limit for depth of water is determined by wiring. Allow your wires to get wet, and the ignition may not fire because the spark will run to ground before it gets to the spark plug. But that's a guess.

Not that I have lot's of rescue experience or anything, but from the basic physics of the situation, driving through water is deceptively dangerous. People typically have the mistaken belief that a bigger, heavier vehicle is safer when traversing water, but that's not necessarily true. A football field-sized super tanker floats just as well as a rubber raft. It's the volume of water displaced that generates the buoyancy, so the bigger the vehicle body, the more water it displaces.

People also often underestimate the power of moving water, even slowly moving water. A slow current pushing against the large exterior of a Suburban is a lot of force per square inch.

In general, I would avoid driving over flooded roads if there's any way to go around since you can't see if there are big holes or objects that could flatten your tires under the surface. But, if I were to proceed, I would not let the water reach the frame rails. Water can rise quickly--or you could drive into a depression which suddenly puts the water over the frame rails--and like I said, it really doesn't take much depth of water to generate enough buoyancy for your tires to lose traction, even in a really big SUV. At that point, if there's any sort of current, you could be pushed downstream and flipped over or sent into deeper water quite easily.

I suppose the only exception to this advice is if the interior intentionally or unintentionally filled with water. Then the vehicle wouldn't really be displacing much water and wouldn't be very buoyant. It's like that scene in the movie Dante's Peak where they're crossing the river in the Suburban and the interior fills up with water. (But they had a snorkel for the engine, too. )

Around these parts, lots of emphasis on when not to drive through water thanks to flash floods (we have what's known as the Stupid Motorist Law ... basically, you pay for the rescue if you try to cross water when it's a dumb thing to do).

From the NOAA website: "a depth of two feet will float your car." Moving water compounds things.

Here's a webpage you might find useful: A Selected Few 4 Wheel Driving Tips.

My experience with 4x4 offroad is limited but in that experience a 'low' range 4x4 often means that the front wheels are going to run at a different gear ratio than the rear...no good for pavement but can be handy for getting up a hill at any more than a snails pace.

Also, how much water you can go through has a lot to do with the design of the vehicle. How high is the air intake for the engine? Many vehicles have snorkel kits available to raise that level. How is the exaust designed? If you stall in hood deep water will water leak into the engine from the exhaust side due to the water pressure? (water in an engine creates hydrolock and can do amazing amounts of damage). How waterproof are the electronics? Will the lights go out if you swamp for example?

You'd think most modern 4x4 vehicles would have this covered...but then many modern 4x4 vehicles weren't designed to see anything but pavement despite what they're advertised to do.

I know a few guys with Jeeps who spend tons of money on countering the whole water thing. I doubt my Jeep Compass could handle more than a couple feet of water and only slowly at that...it's just a glorified station wagon after all

The problem with a flooded road is you cant tell if the road is still intact or has been eroded by current. A good rule of thumb is to keep the water line below the frame rails. As others have mentioned much deeper than that and you run the risk of water shorting out the electrical system AND getting into the vent tubes of the differentials. (the later is not an immediate danger to the vehicle but will cause some expensive repairs if not taken care of soon after a water crossing with any depth) Not to mention the buoyancy risk. I have tried crossing a body of water that was only hub high(half way up the tire) and because of the power of the current it began pushing my truck sideways. However slight it was it was still in fact moving the vehicle and I was nowhere near the frame rails in depth.water crossings if the bottom(solid or soft) and depth is unknown is a scary proposition.

In my limited experience the biggest limiting factor is where your engine gets it's air.

If your intake sucks up water the engine, at the very least, stops. Unless your fast turning it off and very lucky it's toast. If there is any chance of it having sucked up water you need to pull the spark plugs and clear the cylinders before you do anything else. Some trucks and SUVs suck air through a hose that reaches down in front of the wheel well. Which means if the water gets much above the hubs your sunk. Simply relocating the air intake so it draws higher up can make a big difference.

In my experience the wiring isn't usually all that vulnerable. Fresh water isn't all that good a conductor and because the engine compartment tends to get pretty wet anyway they are protected from shorting out fairly well. I would look at where the battery is. You don't want water to get into the battery or let the terminals short out. A sealed battery and/or moving the battery shelf up some might help. A plastic battery box might help keep splashes at bay but if you can't keep the water out you need to provide a drain for it to get out.

This is also true for tail lights and position lights. If they are truly sealed your good to go. But if not they have to have a way to drain. Using silicone dielectric grease, designed for the purpose, to keep water out of the sockets and prevent corrosion is a good idea.

Spark plug wiring are typically sealed under rubber boots with silicone dielectric grease. If your planning to ford streams you would be wise to closely inspect those spark plug wires to make sure thee are no cracks or worn spots. Intact and well sealed they shouldn't give you any trouble.

Of course a diesel would eliminate the spark plug wires as a source of potential trouble.

I'm not real clear on the effects of fording on wheel bearings. I have heard that for just occasional crossing of water over the hubs there is no need to change anything. Just make sure they get regular maintenance.

This is what I have done and so far so good. A couple of times a year I was running a small car deep enough to have water over the hubs during hurricane season. A friend who does a lot of fording streams with a jeep suggested I might switch to a special grease and maybe install some sort of bearing protector. The car kept rolling so I guess everything was okay and now I have a truck. Still something you might ask your mechanic about.

As long as you exhaust system is intact the air pressure of the exhaust gasses should keep the water out. At least well enough for short dunkings.

You might ask around to see if there are any off-road or FWD clubs around your area. They would have experience in your area and be able to look over your vehicle with a critical eye.

having seen videos on tv of folks that have attempted to drive through moving water,

and knowing how slick underwater rocks may be,

and agreeing with the folks' comments above,

and finding your comments and posts insightful and humorous and would be greatly missed - please don't drive through an unknown depth of rapidly moving water - if at all possible.

they can't be paying you enough.

and if you must go, keep the water below the body of the vehicle.

Going by GM specs for a tahoe, your suburban (basically the same setup) should be able to ford through 20" of still water at 5mph. I wouldn't attempt going through fast moving water though. Like many have said here, moving water has a lot of power, a few inches of fast moving water is enough to push a vehicle sideways.

As far as 4x4 low, what it does in a suburban is multiply your torque by about 2 through a change in gearing. Therefore, if you're trying to make it up a steep slippery hill (like a boat ramp or dirt hill offroad) it will allow your vehicle to make it up the hill without putting as much strain on the engine and transmission. This should only be used on slippery surfaces and only at a crawl. The best thing to do would be to check the owners manual, which should offer an explanation of how and when to use it. It's a bit more complex in its operation than 4x4 Auto or even 4Hi mode.

A general rule for water crossings is if you can't walk through it, you shouldn't drive through it. Even slow moving water can sweep a car downriver pretty easily.

If you plan on doing this regularly, there are precautions you can take. There are techniques such as creating a bow wave to help drive through really deep water, and there are preventative measures you can do to keep your car from getting ruined. The air intake is only a part of the problem, you also have to worry about the vents on the axles, transmission and transfer case to keep water out of those areas. Then there's the whole issue with the electrical parts. A good 4x4 book will give you a much better explanation.

If you want to go through really deep water, get a diesel

http://youtube.com/watch?v=tzGh43-leO4

and if that's still not good enough, then you'll need a submarine

If the water is still or slow moving I have had a blazer in the water up the bottom of the steering column. If it moving fairly good you will have to decide whether it is safe or not on site. You don’t have to worry about DC systems shorting out when it gets wet like you do for an AC system. It does help if your fuse box is water proofed and that can be done fairly easy and you can find a lot of sights online about the subject. You can have a snorkel system installed and then to can play submarine if you want.

there are trucks that have railroad wheels attached to them so they can operate either on a roadway or a railroad track. don't know if they are still around - maybe the company has one of them?

I'm not an expert, but I think previous posts have covered the main issues quite well.

Your employer's maintenance contractor should be able to tell you if the vehicle has been 'proofed for water crossings.

If you go through the same crossings regularly, get your crew to pound in metal garden stakes (6' garden T-stakes are cheap) to give a visual indication of the water level. Could save you a lot of grief.

My two-cent's worth.

Interesting, purposely creating a bow wave is actually a water fording technique? I had learned a long time ago that a common reason why cars stall in water is because their owners drive too fast, which forces water into the enclosed engine compartment from the front or splashes up from below, which then chokes the air intake, causes electrical issues, etc.

As an avid off-roader and one that drives through lots of swampy water in the NJ Pine Barrens there are a few things that you need to know.
1. Open the hood of the vehicle on a nice day and look for the air intake. This is your "I can't go any deeper than that" point. If you do you will suck water into the intake and through the carb or throttle body then into the engine. Engine does not burn water. Engine is done, you're stuck and have major repiars to do to engine. Don't ask me how I know this.
2. Before entering water; standing of moving, get some sort of stick and walk throuch the water, measuring how deep it is. Use this as a reference for your intake point.
3. If you think you can make it safely through the water, put the vehicle in 4wheel low with the transmission in low gear and slowly, very slowly drive through the water. You want to cause as little wake as possible. Keep moving slowly, don't stop unless you absolutely have to. If you stop the water that you have pushed with the vehicle will usually come back to the vehile and you may have a wave higher than your intake point.

Slow and steady wins the water race.

I like ducktapeguy's thinking.

I often drive over flooded roads (still-water usually caused by beavers, up to about 30" deep) and I always walk through the new ones first to check for hidden hazards. This will reduce the risk of crossing flooded areas and prevent you from taking a serious heckling from your co-workers for getting stuck and needing a tow out!

As already mentioned, stakes along the edge of the flooded road help gauge changes in water depth and also direct you to stay on the road-bed. Twice I have rescued people who have dropped off the road-bed into the same lake while launching a boat, it is not that the water is dangerous (no current and about 5 feet deep) but that it is a 16km walk out to the highway.

I caught a group of grown men one time throwing big rocks (about 1 foot in dia.) into a large deep murky puddle on a Hydro access road, to discourage other people from traveling into the public area where they were hunting/fishing. It was difficult not to laugh as they waded into the slop to remove the rocks, so an unknowing person driving through the flood did not injure themselves or there property.

Another nasty trick is to pour paint or stain into a stagnant puddle, every vehicle that drives through it after that gets an unwanted paint job.

You do not see things like this often but when you do it can really upset you, most people have much more respect in the woods.

Mike

I should have specified that I don't go into moving water. I'm from desert country and know all about that. DDIS... Don't Do It, Stupid!

The water I go through is like small ponds up to about 100'long. These are areas sort of like gullies alongside the tracks. Actually, they're gullies with deeper gullies on the edges. I heard that one driver rolled his Suburban from the central gully into the side gully; it took two wreckers to drag it out, and they had to move the train to do it.

What are 'frame rails'? Is that about as high as the bottom of the door?

Thank you for all the info. This company is more concerned that you know how to do all the paperwork, more than driving: "Here's a key. There's the car that it fits. Drive it."

Sue

My company's "maintenance contractor" is JiffyLube. Need I say more? My vehicle has been running for three weeks with the 'check engine' light on, at my manager's insistance.

Six-foot T-stakes! YIKES! Those things cost $4.15 each! The RR only made over a billion dollars last year... do you think they're MADE of money???

My crews only run the trains, period. Conductors, engineers, brakemen, switchmen.

Sue

Good advice so far. Slow and 4 Low are generally good. Checking the depth and the bottom is also good. I've crossed a lot of rivers in Colorado, but they have all had good gravel bottoms, good traction. Been in water about a third up my door (old 88 Toyota pickup), probably 3 ft. or so.

If you submerge your wheel bearings, they will need maintenance, as in re-packing. I don't know if that SUV has sealed bearings or not. If so, then it might be a problem. Some other areas that don't like to get dunked are your front and rear differentials, transmission, and transfer case. I routed all the breathers on mine waaaay up so that they wouldn't suck in water. If you get water in any of those, it needs to come out and quickly. One way to do that is to stop for an hour or so, let the water settle to the bottom, and crack the drain plug, but tighten it back up when oil starts coming out - remember water is heavier than oil. It will still need a fluid change soon, though.

If your door seals are bad, find out where the computer is. Usually, there is at least one in the passenger footwell. If that gets wet, it's quite expensive.

Don't let the vehicle stall in the water if the tailpipe is submerged. Water can create enough back pressure to prevent starting, or make it very hard.

Your frame rails are the parts of the frame that run from bumper to bumper. They are lower than the door.

Basically, if you submerge it, it needs fluids changed, bearings and driveshafts repacked. If water gets in, rust soon follows, and that's real trouble.

I put over 280,000 miles on my Toyota with LOTS of off-roading and water crossings, no problem, but I am anal about the maintenance also.

With the addition of the snorkel to my 4Runner it's possible to run in water deep enough to reach the roof as long as it didn't go higher then the snorkel intake. The deepest to date has been to the fenders which would have caused water to get into the stock air intake tube.


Check out this deep water crossing:
http://www.youtube.com/watch?v=c1T7j_PIhew

One other thing no one has mentioned. If you have to cross water deep enough to submerge your fan, either go VERRRRRY slow or disconnect it (remove the belt or if electric, disconnect the wires) or risk deflecting the fan into the radiator with traumatic results. Yes, I know it can happen (thank goodness not to me). On my old Suburban that we use on the farm and off-road I put on an electric fan with a switch in the cab (also routed vent hoses with care, raised the intake to the cowl vent, and moved the computer and fuse block as high as possible),

If you are traveling through the same washes, some of these already have waterline stakes. Check these when they are dry to verify that they are reporting good measures.

Susan, you might want to check out some of your local 4 wheeler clubs. Find one that travels through the woods, not the ones that just go to a mud hole. I'm sure that they would be happy to trade a little driving knowledge for someone that will lend a hand in getting them unstuck.

I drove a Chev pickup truck at work for years (now drive a Ford)and there was a strange thing that happened when I drove through deep water. The front licence plate always ended up getting bent at a right angle near the top, so that it was sticking straight out horizontal. It must have been water pressure from the rear that did this and after every crossing I would have to bend it back down.

Mike

On 4Runners and most Toyota trucks this isn't an issue; the stock fan our vehicles is a clutch fan. The clutch will allow some slip once it's in water so that it won't be damaged or force any of the blades into the radiator. As long as you don't venture too deep for extended periods you'll be fine or else you run the risk of overheating the fan.

That technique can help when the water level is at or near the level of the air intake, it will actually lower the water level in the engine compartment enough to give you some added space around the air intake. What most people do is throw a tarp in front of the radiator to block off the opening, then drive through the water at a consistant speed to create a wave in front of the vehicle. The tarp will block the water from pushing through the front, and drop the level directly behind it. It's kind of like the eddies that are created behind large rocks in a river, the water level will be lower on the downward side. You don't want to speed through the water to create a big splash, just maintain enough speed to create that wave.

If you're at that point where the water is near your hood level, I'd recommend not driving through it. But it could help in an emergency and you had no other choice and were forced to cross.

As a general rule, I'd drive any car through water level lower than the center of the axles. Above the axles and below the top of the tires I'd start to worry. Anything above the tires I'd be really careful and wouldn't try it unless I was really prepared.

Good advice BigDaddyTX, I do the same thing when travelling on ice roads in the north.

Mike

If you wade a vehicle too deep you can face the problem of flotation. If the vehicle floats, or even just take sufficient weight off the wheels, you can lose traction and even a weak current can drag you downstream.

One of the advantages of open vehicles, or rusted out ones, is that they let the water in and pretty much prevent the vehicle from floating. The water rises and I have seen people drive by with only their drivers heads and shoulders above water. In that case the air intake was snorkeled so the truck pretty much drove across the bottom with the driver wearing nothing but a swimsuit and an SEG.

Do watch out for currents. The side of most vehicles offers a lot of area for water to press against. Don't underestimate how much force flowing water can produce. A cubic yard of water weighs roughly a ton. A bit of flotation taking pressure off the wheels, a bit of moss on the rocks and a small but steady current can conspire to produce a sleigh ride you can't stop. Sometimes your lucky if you just lose the vehicle and escape with your life.

Good Tip Art,

I have not seen this flotation problem happen in a truck, but I did see it happen to an ATV.

A co-worker of mine stopped his 4 wheeled ATV in a flowing river about 16" deep, and stepped off the bike to have his picture taken. As soon as his weight was off the ATV it started to drift downstream and we all had to scramble to secure it before it dropped into a much deeper adjacent pool.

Mike

The '06 suburban is the same way; clutch fan. So no issue there.

The newer suburban/yukon uses electric fans, which makes it look pretty funny when you open the hood and see so much open space. It reminds me of trucks from before emmissions and fuel injection. Tons of room under the hood.

Here's a good example of being carried away:
http://www.youtube.com/watch?v=c1T7j_PIhew

Yow, being able to bob around totally out of control in a river is supposed to make me want to buy that snorkel? I kept waiting for the vehicle to catch on something and roll over.

thats actually not how a clutch fan works. a clutch fan is controlled by temperature, when it gets warm enough the clutch engages. It might cool enough to allow slip, but then again it might not, it could get filled with water and get stuck since it wasn't designed to slip.

Depends on the clutch. There are two main types, thermal and non-thermal. The thermal type uses a temperature sensitive spring to control the fan speed. A non-thermal clutch just uses a fluid coupling that slips as RPMs go up. There are also hybrid versions that combine both aspects. I have no idea what GM uses in an '06 Suburban. They've used a couple different setups. Regardless the fan shouldn't have a problem with water sending the blades into the radiator, as the design of the fan doesn't allow the edge of the blades to warp or bend (unless it outright breaks).