My brother’s truck (Mitsubishi 4wd) got partially submerged in the recent floods we’ve had around here, up to about the door sills. It still drives but the (manual) gearbox has been behaving strangely (gear changes sticky), so presumably it got water in. Everything is shut down and he can’t get the truck to a mechanic for a week or so.
I’m in two minds about whether driving in this condition is good or bad. I can see that it might be good in the sense that it would keep the oil sloshing around in the gearbox and ensure everything has a coating of oil and doesn’t rust. But then I can also see that with water diluting the oil it might be bad due to lack of lubrication.
The oil will want to float on the water, especially when stopped. When running you may get an emulsion but I would be very wary.
My intuition would be to try to get under the truck first thing in the day and pull the drainage plug and see if you can drain the worst of the water. Not an easy or pleasant task I grant. If you could access replacement oil just drain and replace.
I have a bad feeling that the internals will corrode very quickly if water remains. So the sooner any prophylactic action is taken the better.
A real mechanic should hopefully be along real soon.
I once asked a question about restarting a flooded car for the first time. The well-reasoned opinion in the thread was to at least drain the water out of the gearbox before even starting it, let alone running it. The the gear oil will float on the water. The water from the bottom will be sloshing around on the gears doing most of the lubricating, which it won’t do well. The water will promote corrosion in parts that aren’t ordinarily exposed to water. I would say, at the very least, get it on jack stands, let the water settle into the bottom of the gearbox, then drain until clean oil starts flowing out. Quickly recap it, and top it off with clean gear oil. If you didn’t let too much gear out oil when draining the water, you might be able to get away briefly with driving it slightly low on gear oil but I wouldn’t push my luck on that. Transmissions use a lot less oil than engines, so even a small loss of oil could be significant. Good luck.
I broke a rear end in a race car I had due to water in the rear end housing. It was common back then to vent the rear ends with a 90 degree elbow and a length of hose. This allowed us to use a bit more rear end lube, this would keep the rear end gears lubed even during hard cornering. Not sure how the water got in but there was a bunch when I drained the rear end. I wouldn’t drive the truck.
You seem to have water in what you are calling the gearbox (manual transmission). You also have three other gearbox type areas with gear lube in them that also should be drained and the fluid changed. If the transmission has water in it these other gear boxes probably do too.
The rear end or differential, and since it is 4 wheel drive you also have one of those up front too, and a transfer case that the drive line to the front wheels and the other drive line to the rear wheels go. These are all full of gear oil.
These repairs could add up quickly if you don’t change all these fluids. Take care of the transmission only and next one of the differentials goes out, fix those then the transfer case goes.
Full fluid service and while you are at it your oil pan may have water in it, so an oil change is in order. Don’t even start and run the engine without an engine oil change. Water and oil make an emulsification, which is great on salads but not so much in cars.
Regarding the engine oil; since the truck has already been driven check the dip stick to see what it looks like. Also the oil filler cap. If you see milky looking stuff on either, that is emulsification, blending of water and oil. Some on the filler cap can be normal, any on the dip stick is a danger sign.
I’m an engineer rather than a mechanic but I’m quite familiar with gearboxes and tribology and I can confirm what @Francis_Vaughan and others have cautioned is true. The problem isn’t just the water itself displacing the oil but the fact that there are tiny shavings and particles of steel from the gearing that are suspended in the transmission fluid, which occurs as a normal part of break-in and wear. These particles are ordinarily not a problem because the gearing is designed to have enough clearance such that they remain suspended in the fluid as individual particles causing only a small amount of erosion of the gear surfaces; however, with exposure to water they will form iron(III) oxides (also known to lensmakers and jewelers as “red rouge” or buffing “compound”) which will both clump up and wear on the gear surfaces that are already poorly protected by the emulsified oil/water mixture. This, in combination with the water potentially facilitating corrosion cracking anywhere that their might be an incipient crack in the hardened surfaces will generally cause premature failure, sometimes within just a few hundred hours of service.
If the vehicle has been submerged to the point that you can see water in the transmission fluid (the milky fluid that @Dallas_Jones describes) then it will need a teardown, thorough cleaning, and rebuild if you want to have confidence that it won’t start grinding and come apart like a cheap watch at a most inconvenient time.
If it were me I would have drained the oil from gearbox, and both diffs, and checked the engine oil, before driving but it’s not me and my brother is several hours drive away, so I can’t help him directly.
I already had my brother check the engine oil. It’s OK. Thanks also to SoaT for the point about metal particles, hadn’t thought of that.
Anyway it sounds like it’s academic because apparently it won’t go now. I suspect the vehicle is write off.
Well, maybe. You say that water was up to the door sills, so presumably it didn’t get into the air intake, fuel system, or electronics. A transmission rebuild or replacement isn’t trivial but if the vehicle is otherwise in good condition its worth getting a mechanic to at least look it over. On the other hand, if water has gotten into the intake and up into the cabin, it is almost certainly a loss without a ‘frame-off’ restoration.
Very old vehicle only probably worth a few k. If it needs a reconditioned transmission and serious work on diffs, and a few other bits and pieces, that would be more than it’s worth, probably.
I normally do the major work on it, just to keep it running for my brother at low cost. But I’m not sure I have the energy…
I kind of figured being a Mitsu truck, but then, people rebuild MGs and Triumphs that came out of the factory with negative value and basically require having a second vehicle as a ‘parts car’. Sell it for salvage and buy a Tacoma/Hilux as a replacement.
We don’t get the Tacoma in Australia and the Hilux has become overpriced here no doubt due to its “legendary” status hyped up by Top Gear.
It will be a bit sad if he has to sell it. We’ve been keeping it going long past the point where it was sensible to do so, as a bit of a silly project.