Not sure, but I can say that I've never shifted mine in or out over 30 MPH. Not because I've set a limit, just my driving. If it's icy/snowy/muddy enough to require 4x4, I'm not going to be going much faster than that for safety reasons. If I'm coming up to a snowy patch of road I'll just slow her on down and throw it in 4x4. No reason to risk blasting through bad road conditions at high speed even with 4x4 (even though many Land Rover drivers may think they're invincible...).

 

the highest speed limit to and from work plus anything over 50 it starts vibrating at 65 it vibrating bad

 

That's a good question that I've always wondered. I am not going to risk finding out though. I either stop or do it in a slow roll. Never with the throttle on. I've done it probably at 10 or 15 mph.

 

I've done it up into the 40's MPH, push the clutch in, throttle down, treat it just like shifting gears.

 

Always what I've done too Tyler. But I've wondered about what madpogue mentioned.

I've been told by people that with the fords you can drop it into 4wd just like shifting at higher speeds...

 

Yes, you can that with autos too, and you should do it if there's a chance of unexpected ice/snow because the autos will not lock in at higher speeds. When I had mine, I had to almost come to a stop before they would lock in.

With either manual or autos, you can shift at any speed because the rotation of the front tires is turning the axles, diff, and driveline the same speed as the rear; it's just not locked at the tcase. Of course, if you have need of 4hi, you had better not be going 90mph!