3406C crank problems - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 2 (permalink) Old 10-22-2019, 03:28 AM Thread Starter
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Hey guys, been lurking for a long time, first post. My 3ZJ 3406C laid down on me last week. Started with a very minor vibration early in the day, then all of a sudden it got worse, then she started shaking and bucking. Pulled it over, towed it home. Found the crank broke right at the front of #7 main.
My first question is what should I check, damper will get replaced, what else would cause this? Was running light, no sudden shock loads happened.

Next thing, how common is it for the block to be savable after this kind of break? The flywheel was rocking back and forth pretty good. I will have the crank bore checked and the block crack checked, unless the resident gurus think that would be a waste of time?

Last question in this novel, is the best place to source a crank. Cat wants $7k+ for new, and similar for ground reman, since I have no core. I don’t know if any of the aftermarket cranks (Highway and heavy parts, Abilene Machine) are worth a damn, and I really don’t want to put a ground crank in it. I can find late E model/C15 cranks much easier and cheaper, like a 0R9906, will one of those work? I thought the newer rotating assemblies could swap in? Or am I better off looking for a good magnafluxed original CAT crank? Planning on running 10R1439 packs, if that matters.

Thanks in advance, guys!
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post #2 of 2 (permalink) Old 10-25-2019, 02:49 AM
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I had a crank break in the same place once. The engine ran very little after it let go. It put a slight ridge in the rear main bearing bore in the block and cap. I was able to carefully remove the ridge and put a new bearing in with no lingering problems. The rest of the engine was in good shape so I took off the front and rear housings, stood the engine on end,. Took all the rod and main caps off and replaced the crank without tearing anything else off. Took a lot of meticulous care but it worked. The worst part was trying to get the engine tipped from vertical to horizontal again. That was really hairy.
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