So as long as you are on a slippery surface, as in you are driving on snow covered highway, it will be fine. 4 Low is when you can't exceed about 20mph. You do not want to be driving on a dry highway with 4wd engaged, it can damage the system. Your specific 4Runner should have in the manual the details about your specific vehicle. I own a 2008 GX470, and owned a 98 4Runner, both were a bit different 4wd systems. Both also should not be driving on dry roads.

Keep in mind that if you are able to go 60mph, why would you have 4wd engaged anyway? I live in upstate new york in the mountains, and I only use it if I am in a situation when I am losing traction, like going up hill covered in snow and icy.

Also, 4wd won't help you stay on an icy road going around curves etc. 4WD just helps get you moving. Tires and good driving help you not fly off the roads.

Our vehicles get bad enough gas mileage, don't make it worse by using 4wd when you don't need it. 🤣 

You should use it at least 10 miles a month or so, to keep the system in good working order.

if the conditions actually warrant using it then sure. That's what it's there for. Check your owner's manual for limitations. If it's that bad, then I'd think you should driving cautiously anyway. 70mph in slippery conditions sounds like suicide to me.

Your owner's manual should address this. It should not be a problem if your 4WD system has a center differential.

Also, for future reference please use the length-limited address line for a short description, not your full post which in this case appears to have gotten cut off. If there is any additional information you can post it here as a response to your original post. Thank you. (Title edited.)

I asked this the other day. See what others wrote: https://carkiller.com/scottykilmer/postid/315649/