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I've got '95, 2500, 2WD with 430,xxx on the odometer. Love this truck! I've had it for 20 years, and it's never made me walk. Trans is an ATS Stage IV, with 323,xxx on it. Truck runs great. My question is does Cummins specify a mileage to change out the connecting rod bearings? Somewhere rattling around in the back of my mind, is a sticky note saying yes, they do, but I can't find anything on it.

Here, I'm towing my hillbilly RV out West.

 

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No, they do not. When I tore my 800,000 mile engine down there was a slight bit of wear on one set of rod bearings. IIRC it was the #5. The only other thing I found was a small crack in the #6 piston. The measure Cummins uses that I've heard is oil consumption. In my case it was qt every 800 miles. The best way to find out if you need bearings is by an oil analysis. High lead and/or copper is the tip off.
 

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Thanks Ames. I used to get an oil analysis every few years. I'll do it again. Mine is using 1/2 qt every 5,000 miles.
 

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The Uppity 12v Guy
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Bottom-end bearings, piston rings, etc, do not have replacement intervals.

Gary, that's really not bad for 800k given that I've seen engines with less than 300k that looked almost that bad. When I tore down my original engine at 334k, there was just the faintest whiff of copper showing on the upper rod bearings.
 

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The Uppity 12v Guy
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Eh... it's complicated. My job requires testing new performance parts and I needed to make sure the shortblock was ready for 800-1000hp.

It had nothing to do with the condition of the engine, it easily could have gone another 150-200k at the ~500hp I was making before teardown.
 

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Eh... it's complicated. My job requires testing new performance parts and I needed to make sure the shortblock was ready for 800-1000hp.

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Must be nice..... not many guys can say their job requirements include having a 1k hp capable truck!!!!
 

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Interesting! Thanks for posting that. My main requirements are twofold--a good husky tow machine and great reliability. The only HP/Torque upgrade I've got is a #6 plate in the injection pump, but that's plenty for me.
 

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The Uppity 12v Guy
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It's not all sunshine and unicorns. The flip-side is all the prototype validation that takes place on stuff "while it's apart anyway" and then inevitably becomes the delay to reassembly makes for an incredibly drawn-out build process. Then when waiting on others in the company to have time to do their part (as some projects objectively aren't the highest priority for the company)... yeah. I'm ready to be done for a while. Luckily, the guinea-piggery it's slated for next requires substantial mileage to be put on it for the forseeable future.

Even with everything I get to take advantage of, it's not a poor man's game either. Not by a long shot. It started as a voluntary transmission swap. I was actually money ahead going from my G56 (sold as a swap kit) to an 850/1000hp hybrid auto trans with a full-manual valvebody. Then things started to go sideways. Engine came out "while it was apart" to refresh it and set it up for it's new life 800-1000hp lab rat. The 5.9 build turned into a P-pumped 6.7 12v build, I pulled the trigger on personal projects while the truck "was down anyway" for company projects, and by now the retail cost on everything that's happened to my truck in the 16 months since I started my "transmission swap" would be approaching $40k. That's retail cost on parts and labor at a fair, billable rate for the completed task. Actual labor, time spent figuring everything out, etc, would probably be another $20k on top of that.

It's been a journey. I learned a lot. I'm better for the experience. And everything, no matter how fun at first, eventually turns into work.
 

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My 1996 has 469000 miles on it doesn't use a drop of oil. I always told myself when it gets to 500000miles I am going to rebuild it. But idk it just runs good.
 

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Gary, that's really not bad for 800k given that I've seen engines with less than 300k that looked almost that bad. When I tore down my original engine at 334k, there was just the faintest whiff of copper showing on the upper rod bearings.
The weird thing is it didn't have much blowby so I kept looking for cheap easy fixes to combat the oil consumption. It didn't have one leaking gasket and I even replaced the valve seals. I finally succumbed to the fact I wasn't going to get a million miles out of it since my oil/fuel mixture was resembling a two stroke engine. My oil sample days didn't start until the last engine was installed and I decided to extend oil drains based on oil quality, not mileage. I'm sure they would have caught the lead and copper from the pictured bearing.
 

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My 1996 has 469000 miles on it doesn't use a drop of oil. I always told myself when it gets to 500000miles I am going to rebuild it. But idk it just runs good.
I wouldn't touch it. The oem internals are better quality, IMO, than you could find to replace them with. At 450k my engine is using a qt every 2000-2500 miles and I didn't skimp on quality rings, bearings or pistons. I just didn't buy them from Cummins.
 

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Yeah I probably wont touch it. If I do rebuild it. It will get cummins pistons and rings
 
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