1989 Chevy 3500HD broken crank..HELP

dylaferd · October 5, 2016

Recently bought a 1989 Chevy 3500HD dually and it had a broken crank so i pulled the motor out a new crank in it and 5 miles down the road the crank broke again... it was a re-manufactured crank. i'm hoping that's not the problem. also wondering if it's the harmonic balancer? if anyone's had an issue like this or has any suggestions will be great.

StepsideGMC · November 1, 2016

Is the harmonic balancer in rough shape? Did it run smoothly for those 5 miles?

etex211 · November 1, 2016

When you installed the new crank, did it spin over easily in the block with none of the rods hooked up? Is the original crank and the new crank broken in the same place?

What kind of engine is it? 350 cranks and 305 cranks often get interchanged incorrectly. They have the same stroke, but the counterweights are different.

Overtightening the belts can cause the crank to break near the front.

I can't see the dampener causing the crank to break that fast, unless it is an externally balanced engine and the dampener is the wrong one. If this is the case, you would have definitely felt it.