It seems I just can't win with this truck! I just completely rebuilt this engine about 6k miles ago, ran into a minor oil consumption issue early on and straightened it out. Just put a brand new rebuilt A4LD trans in, I thought for sure we had this thing licked... it had been running great. Until I get a call this afternoon the GF said her truck died, someone helped her get it off the road and into a parking lot. She popped the hood to see what happened and discovered the crank pulley/balancer came off! She called me back to tell me this so I came out there with my F250 and car trailer I hauled it back to my shop. My buddy and I got it inside, after further investigation it turns out the end of the crank snapped off inside the pulley/balancer! Has anyone ever heard of this happening on these engines? It's the craziest thing I have ever seen, I have seen cranks break inside the engine on one of the journals but not this! Any idea what could have caused it? The retaining bolt didn't back out. Any and all input is appreciated, thanks!
John

 

That does seem very strange. I've heard of this with guys that run big superchargers driven off of the crank. The additional drive belt usually wraps around a pulley at or in front of the stock pulley, and it puts a lot of additional stress on the end of the crank shaft. Do you know if this was done in a past life of this engine? I know that the 4 liter engine was not a popular one to supercharge, but it has been done by the likes of BBK.

 

Yeah I could see that, we're not running a supercharger on this one. I guess it rules that one out. The only thing I can think of is maybe the balancer was out of whack, or maybe I overtightened the retaining bolt. This is just crazy, I can't believe it!

 

The same thing just happened to my friends ranger. Not sure what year it is but it has the 4.0. We couldnt figure out why it wouldnt start, happened to look undernith and saw the crank pully just hangin there! No one can believe it just broke off for no reason. He still has 2 payments left. What a let down. Wish there was a way to weld it back on or smthin. Sucks for him.