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schaef_12

The day the tranny died.

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just got done working my POS Injectors over (thats another story all of its own) and the truck was running better then ever, shifted from 4th into 5th and pushed on the skinny pedal and BAM ripped out 5th gear. Something else is screwed up in there too, it likes to lock up in reverse all 2 days before the freaking dyno day.

Just a story for now, i might have it going by tomorrow night. Pics to follow

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Sorry to hear that! Hope you can get it going good again that soon!

(Why does there always have to be a 'weakest link'?)

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Yup, I pulled the back cover off the tranny today, and found just about every tooth from 5th gear in the bottom of the transmission, reverse is smoked too. As of now I am going to put a new 5th gear and syncro and reverse in it and call it good. I have to pull the side covers off and make sure other gears aren't screwed up but i'm pretty sure the 4 other forward gears are just fine.

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Yup, was going to tell you that reverse was probably acting up because pieces of fifth were piled up around it.

As a warning. Never pull in fifth below 1800 rpm. You will destry the teeth or rattle the gear off. Same problem with the 5600 build I posted.

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This is really good to know. Thanks Chris!!

(So it should be ok below 1800 rpm in a high gear as long as there isn't much load on it? Just to clarify: As long as the truck is empty and not pulling very hard at all, then lower rpms are ok? As soon as you have to give it some boost or accelerate more than just softly, then make sure you get the rpms above 1800 by downshifting?)

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5th gear is a week link because well, its a small gear. With my 4.10 i'm hardly ever pulling below 1800 rpm. Mine let go right around 2200, granted it was the same time that the boost gauge touched 55.

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This is really good to know. Thanks Chris!!

(So it should be ok below 1800 rpm in a high gear as long as there isn't much load on it? Just to clarify: As long as the truck is empty and not pulling very hard at all, then lower rpms are ok? As soon as you have to give it some boost or accelerate more than just softly, then make sure you get the rpms above 1800 by downshifting?)

Being easy on a 4500 and 5600 is actually worse on them. Cummins are the only one's with 5 gear problems in the 4500. Why? Because a Cummins is the only one that can build power down low. It is all about harmonics. The damage is usually started way before the failure. Ever seen the lady break the glass with her voice? Well the same thing happens on a transmission. It weakens and fractures the teeth. Harmonics is also the reason that 4500's have the dreaded 5th gear nut failure. Ever heard your trans talk back to you when in too high of a gear? Well if you have you have started on the path to damage. I have ridden with alot of guys that think it is cool to shift way too early into OD and watch the Cummins pull hard and build boost. Cool yes, but also detrimental to the trans. I know there are nay sayers out there, but if you keep your rpm's up in OD especially, it will last along time without failure.

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