Manual hubs locked on the highway, what might be broken?

[dm1333]

A neighbor left the manual hubs on her Toyota locked and drove on the highway. When she got back to the apartment complex there was a little smoke coming from the back of her front wheels and you could smell the grease that was cooking.

My knowledge of 4 wheel drive is just about nil. What should I check on her rig and how should I check it? Bearings? Is there a way to check the hubs? The CV joints? I figured I'd check here since you guys have given me some good advice here before.

[kamesama980]

go to a toyota truck forum and ask. if it got hot enough to smell burning grease and see it smoking, you'll probably need new wheel bearings/hubs and lock assemblies. NOT something you want to be doing yourself if you don't know what you're doing.

[JanGeo]

Probably cooked the differential oil too - what happens is the tires are different diameters from normal 2 wheel drive wear and she was loading up the gears a lot extra when the wheels were sticking to dry pavement turning at different speed but coupled together by the 4 wheel drive (if she was in 4 wheel drive). On snow or slippery surfaces it is not a problem but on dry pavement it can be if there isn't a limited slip coupling between the front and rear wheel drive trains.
She should have noticed something was wrong but sometimes people just give it more gas and keep driving.

[kamesama980]

leaving 4wd on around town will smoke the tires before it smokes the diff. a front diff isn't any less ballsy than a rear diff. on the highway, the turning radius/distance thing won't matter and again, it'll do the tires in before the diff and won't bother the hubs. it takes a LOT to smoke a toyota diff. I had a friend drive a cressida...well lets just say stupidly fast very often and for at least 500 miles with no oil before it finally siezed up on the highway doing 90+ and ate itself. then drove another 15 miles after letting it cool down.

I'm now wodnering if there's a warning in the glove box manual saying don't drive over 55 with the hubs locked or something and she was doing 70+ on the hwy... overspeed/overheat the bearings and poof, she let out the magic smoke that makes things work. Either way, I'd bet it's an older truck and the hubs/bearings haven't been serviced/lubed in a while.