I have done the same thing and only noticed it after many many miles when the front tires started digging into blacktop on a slow sharp turn-------the fan switch can sometimes be mistaken for the 4X4 switch, no harm, maybe even good since it no doubt churned up the oil in the front differential and got rid of any condensation

 

 

Mike,

I got a three year old too. He's done that 4x4 switch thing to me more than once. Every time he gets into my truck, he switches it to 4x4 and mostly to low. One day I was leaving for work and taking him to school and as I was backing out of the driveway I kept on saying to myself, something is wrong here. That's when I looked and I was in 4 low, hmmmm. I looked back at my son and he just smiled.

I look for that now when he's been in there without me.

I think you're probably okay as 4 hi is fairly forgiving, however 4 Low would be a totally different story.

~DM~

 

Selecting 4HI or 4LO creates a direct mechanical linkage between the front and rear wheels through the transfer case. In effect, the transfer case tries to turn all four wheels (well, really the front and rear wheels that are receiving power at any given moment) at the exact same speed. The fun begins if the front set of tires is (through different degrees of wear or different inflation pressure) a different diameter than the rear tires. Under these circumstances, the front tires will want to spin at a different speed than the rears at any given road speed. In 2HI, no problem. The front tires are freewheeling, not tied into the transfer case. In 4HI or 4LO on a slippery surface, the front tires can easily break traction briefly (skipping or stuttering) to relieve stress on the drivetrain created by the different tire diameters and rotational speeds. On a high-traction surface, like dry pavement, the tires wil have a more difficult time briefly breaking traction and certain components in the 4WD system may "wind-up" instead, in the worst case leading to broken or permanently twisted parts.

It sounds like you were lucky. In any event, I would find a dirt road and activate 4HI and 4LO to verify proper operation.

 

Like someone else mentioned find a good dirt/grass road and verify correct operation. I would almost bet no harm was done, I've hit 65 mph in 4wd HI. If you are really worried I would change the front diff grease and the t-case fluid. I'd say it's big case of no harm, no foul.