Hi Everybody,

I purchased a used 2014 4R SR5P with 52k miles in the beginning of October. I had no issues the first month but the first time I used the 4wd I noticed a burning smell in the rear wheel wells. I've smelt it off and on since that first drive in 4wd - usually more so after a decent trip and not so much after a quick trip to the store. It seemed to be letting up and not smelling as much until yesterday when I had to use the 4wd again.

anybody have any ideas before I call the dealership tomorrow? It's still under warranty for a couple thousand more miles....

Before going to the dealer I would make sure you can recreate the conditions that produce the burning smell. Then when you go, have a tech and or service advisor go with you when you do it. That way you won't get an unable to duplicate problem or notice any issue from them. Go ASAP if your warranty is about to expire. It may take then a while and a few trips to work this out.

Even though the burning smell seems to be from the rear wheelwell, I wonder if it may actually be something on the front half of the truck that may be the issue when 4wd is engaged. The reason I say this is because the truck is by default RWD. This means under regular driving, the burning smell would be there all the time if something is wrong at the rear. But because you only notice it when in 4WD, it's likely an issue at the front wheels/differential. Best to have the dealer take a look while it is under warranty.

Keep us posted, so far no one has been able to get any dealer to cop to an explanation for the burning smell.

Sometimes the rear wheel burning smell can be hot brakes as the stability control systems need to work harder in some 4wd scenarios. I can't say that this is your problem specifically, but there really is not much else in the 4wd system specifically that would cause a burning smell...

Now that I think about it, you should check under the vehicle around the front driveshaft area to see if any of the grease from the joints at either end has spun onto the exhaust system. When they were doing the maintenance before selling the car, they probably lubed the driveline. The front driveshaft is disengaged when 4wd is off and will only spin when engaged. If it flung some of the grease from the joints on to your exhaust system, it might cause a burning smell that would linger even after the 4wd system is disengaged. Thats about as good of a guess as I have. Good luck!

is it a hot rubber smell? if so i bet it's the normal smell and is just a coincidence that you noticed it after using it in 4wd. I don't think anyone has a concrete answer for the cause.

FWIW, if you're driving in a region that uses liquid de-icer on the roads, these chemicals can create an acrid smell when splashed onto hot components like exhaust or brakes.

Thanks everyone. I have an appt on Monday. We'll see what they say

well I took it in and it needed a front differential, rear differential, and transfer case fluid change. Stupid me figured that would have been taken care of before I bought it but apparently not. They took it for a spin in 4wd and didn't notice any burning smells so I guess all is good for now

A lot of times people sell seemingly good vehicles because they are damaged.

Did they show you the used gear oil?

I bought it from a Toyota dealership, not some sleazy used car lot. It's under original warranty, came with a warranty from the dealer, and had a clean carfax. I'm not worried about it being "seemingly good."

I asked about the gear oil but the service tech didn't seem to think that was the issue. Also, if that was an issue, wouldn't I smell it every time I drove it?