99 Ranger 3.0 4x4 5 Speed 220,000 miles

​​​​​Don't know if this has happened to any1 else, But ever since I got this bout a year ago, I've had a vibration that i haven't been able to fig out. Had bucking taking off , put new flywheel, cluch, plate etc. Had tires balanced, new front drive shaft, new u joints in rear.when i had trans out, pulled top off just to check. It looked ok from what i could see . I was coming bac from MO and doing 70 on fwy it was running fine, still had the vibration but didn't seem to bad. Then something blew. Got it towed bac home, didnt even want to look at it for a couple days. When i did, looked like starter was loose. So got under it and starter had corner of case where it bolts up broke off. I had checked all fluids b4 i left and trans was full. Until it ended up all over the fwy. I no i need a new trans, but any ideas on what could have caused this ? Haven't had time to pull it out yet. Thanks Dave
Update. I pulled the driveshaft+ skid plate to get a better look . Well it's not just the corner where starter bolts on, the crack isn't just a crack it's broken in two. It goes all the way around. If i wiggle the tail shaft i just it moves with about 3/4 s of the trans and the front is of course bolted to motor an doesn't. I mean i can move it enough to see into the trans. I will say I've never seen a transmission case as thin as this aluminum is.. once i get it out i ll take some pic s. Not sure when, i ll prob find a trans 1st.

 

There are alignment dowels or sleeves on the engine block and alignment holes for them on the transmission bell housing, 1 on each side
These are there to line up the crank shaft and transmissions input shaft, so they are PERFECTLY aligned, other wise vibrations and what you had happen
Trans bolts can not align these 2 shafts good enough, need both those alignment dowels or sleeves

But an input shaft bearing can also fail(in transmission), causing the same thing
I would think when you did the clutch and flywheel you would have noticed a lot of play in the input shaft?

Long shot is a bent crank shaft, but oil would have been coming out of the rear main seal and you would have seen and mentioned that

Because bell housing broke it would be an engine trans alignment issue
So Transfer case should be fine

 

Ya eng and trans r aligned and it had the same vibration b4 i pulled the trans for new clutch etc. check my update. The brake isn't just the bell housing it goes in2 the trans 2. Never seen anything like this in my 50+ years of working on cars an trucks