Bad Smell only when window is down...Smells like propane

not told what leaks and to where.
we can no see leaks blind in text box.
axles?
autotrans
manual trans.

cause are only 3.
bad gaskets and seals
overfilled. (never do that)
or on ENGINE ( )PCV valve clogged and engine pushes oil out
rear main seal and to the TC and bottom bell housing leaks oil
and is not the transmission, leaking. fooling owners.
oddly
other causes, 4wd axle vents clogged with mud or bug nests>

no engine told
no transmission told at all(options day1 new car)
RWD
Front; with Mitsubishi R4A51 Transmission
or Front; with Mitsubishi V4A51 Transmission

hi Kemal.

1. Park your vehicle overnight on a clean patch of pavement or a large, clean piece of white paper.Either tape some sheets of paper together or buy a roll of plain white commercial wrapping paper. Newspaper is too absorbent and can change the color of the stains.
2. Place marks on the paper.
   Show where each of the four wheels is resting, and indicate the front and rear ends of the vehicle.
3. In the morning, move the vehicle and look for small puddles or traces of liquid on the ground or paper.
   Touch and smell each puddle or trace of liquid.

Here's how to decipher the evidence:

• If it's clear, watery, and under the air conditioner: It's probably normal condensation if you've used the air conditioner recently.
• If it's black or dark brown, greasy, and located under the engine area:It's probably oil. Figure out which part of the vehicle was over the spot. Look under the hood around the oil filter and the engine and under the vehicle for leaks around the oil drain plug, the crankcase, and the oil pan below it.
• If it's thick, black or tan oily liquid: Gear oil may be leaking from a manual transmission, the differential, an axle, or the steering gears. Any of these leaks needs immediate attention.
• If it's red, pink, or reddish-brown and greasy and you have an automatic transmission: It's probably transmission fluid. Check the transmission dipstick, and if the level is low, top it off with the proper transmission fluid. Then check the dipstick again in a day or two. If it's low again, have a professional check the transmission to make sure that the seals are intact.
• If it's watery or slippery; green, red, blue, or yellow; and is coming from under the radiator or engine: It's probably coolant. Check the radiator, pressure cap, engine, and hoses for leaks.
• If it's oily; pink, red, or clear; and you find it toward the front bumper (usually on the driver's side): It's probably power-steering fluid. The power-steering system is sealed and shouldn't lose fluid. If it's a light-colored or clear fluid: It may be brake fluid. Even if the leaks have dried, the stains should be visible. Leaky brakes are too dangerous to leave unattended. Have a professional repair any brake fluid leaks immediately.
  
• If it smells like rotten eggs: It's battery acid. Avoid getting it on your hands or clothes and have the battery replaced.
• If it smells like gasoline: It probably is! If the smell is coming from under the hood, check around the fuel pump and the fuel injectors - or the carburetor if your vehicle has one. If the leak seems to be under the center of the vehicle, check the fuel lines. If it's under the rear end, check the fuel tank.

blace?
is car 4WD?
ok, is this your first car?
is this your first car with A/C? for first time ever using and A/C?
(btw front defrost mode uses A/C functions)

if pure water, its just A/C condesate, 100% normal all cars.
today cars have a wide variaty of new fangled fluids.
in the olden days we had tan, and green'
now its many.
toxic AF (antifreeze) green, pin, yellow, red, orange , etc. now.
Engine oil think goodness is just tan/brown or black
pull dip stick gander at the tip (THAT is your color today)
now the transmission, A./T automatic, it usually is pink, but can be
read or dark red. (if your year has a dip stick on A/t pull it and bingo your color is there)
then there is the leaking, (rare) window washers. (can be any color)
but is soaping to the touch.
last is M/t boxes. manual gear boxes,, and transfer case (4wd)
the they can be , clear to brown. my synthetic is clear but is very viscous, and smells sweat.
Some axles and transmissions have (gear boxes) have hypoid gear lube that is brown and stinks to high heaven.. nasty smell.
But this too can be different today, and be any color, from clear to purple to brown.
last is brake fluid, its always clear, but in large volume or old is amber.
it smells sweet. and sticky.
that is what we have today.

find your cars A/C condensate drip tube under car
and memorize that location, then when it leaks, you know.
its that.
on some cars its at passegers toes.
on my jeep its dead center, of car.

You need a full service of the auto transmission. Check the oil condition for burnt smell.
The oil may be burnt out and fails to lubricate when temperature goes up.
But most likely the gear gaskets or gear teeth are worn out.

you have an electrical gear box but it still works on oil presher and clutch/brake bands,,,if there slipping first check the gearbox oil is full and the colour of it,,it shouldbe red,,if its a dark brown and smells burnt you need to have the gearbox looked at,, do this sooner than later as the longer the box slips the more its going to cost you fixing it,,

The most reliable and tried and true method is to check the transmission oil. Check it for...
1. Correct level
2. Right colour: a nice light red. (or somtimes yellow) not brown
3. Smell, it should have a not unpleasant smell, if it smells 'bad', it is starting to break down and will attack the friction material on clutch packs and brake bands.
4. Remove the transmission oil pan and check it for flecks of friction material, metal filings and pieces of rubber.
If any of these things are present, you have, or will soon have a transmission failure. The whine could be the transmission oil pump, the gear set is known to to come incontact with the pump body causing whining noises and creating metal filings which cause the transmission valves to stick..

The rear diff. turns the rear wheels. It is located in the middle of the rear axle. It won't last long if you ignore it. May just need dearing's but if it is driven the cog wheels will grind to dust or drop off this can cause the rear axle to seize up and can be a danger because the back wheels will lock up. If you are going to fix it yourself let me know and I will be able to guide you through the process

It seems as though the Transmission clutches are slipping if it's an automatic or the clutch is worn if it's a standard. If it's an automatic transmission check the Transmission oil it should be clean and no burnt smell. You will easily recognize burnt oil by it's nasty smell.

one of the best ways to tell what is what is to open the one that you want to add first and smell it...then remove the cap of the one you think it is and smell that ...