Crankshaft Blues...

[gwaidman]

Well, the noise {see 'strange grinding sounds') and clatter turned out to a crankshaft. Nice. We dropped the tranny out of Greg's truck and it seems the crank is sheared at the flexplate. It this the usual place for cranks to break? Heres the kicker... 50k on a GM Goodwrench crate motor. I was shocked to say the least. I even had $5 that said it was the tranny. Anyhow, the guy likes his truck (98 3500 crew cab)and I'm thinking that maybe we can get away with a new crank, this motor was really tight. Is a rebuid necessary? Or, should we go with a rebuilt? 65ldiesel.com as some very attractive pricing. Please, your thoughts! :rolleyes:

[rjschoolcraft]

Thouroghly inspect the block for cracks! Look up my post and check out the pictures for what to look for.

[gmctd]

Mine sheared the flexplate at the crank........

[tom.mcinerney]

If there are yet no web cracks , I'd advise install splayed main caps from Kennedy , since we know '98 blocks are crack-prone.

I'd like to know how the cheap rebuilds are , but if i have to replace an engine it'll be an avant rebuild or new GEP reman from Kennedy.

It would be great to have statistics on the cheap rebuilds--must run for a while--but with normal heads and blocks subject to cracking, these are risky enough as it is.

[gwaidman]

Hmmm... Well, I lent my rig to our unfortunate friend for a few weeks. He has a skid steer that need to finish up some work before we tear into the engine. From what I can see, the crank is sheared clean right before the flexplate. Once we pull it, we'll check for cracks and go from there. It would be realy nice to install some reinforcement in there and get away with only replaceing the crank. If an engine is needed, it may be better to buy from a known source and get it right the firts time around. Will update as progress is made. Hope to have a few photos as well.

[tom.mcinerney]

Due to the fact that many blocks have cracked, it should be possible to get a good used crank.
More Power did a very very good article about the harmonic balancer , and crankshaft failure issue.
If the balancer is fresh, the cranks generally last. {Regretably not your experience}. Check the balancer and the keyway/woodruf key in the crank carefully, too.

[ace58]

If the crate motor is a Navistar new style casting without any web cracks, I would have no problem replacing the crankshaft (and harmonic balancer)