Mine was alot like that. Got real loud and blew ALL the oil out at freeway speeds. I thought for sure I blew it up. Thank God I was wrong! It blew a hole in the piston and had huge amounts of blowby at 75 mph, pressurized the crankcase hard and fast and roughly the speed of light (or maybe even sound, IDK) and forced all the fuel from a cracked injector into the crankcase. I was not feeling too good but could find no hole in it. After pulling the head I found the problem. Luckily, the diluted oil wasn't ran very long and all the internals were still ok. Crank and all rods were in good shape still. ... ... ... . I should have it put all back together by the end of next week!
Maybe your story will be similar? All you can do is hope and pray.