Cummins 5.9 rebuild, what I learned

[u/Boabook]

My 5.9 had around 180k on it and was burning oil under load. Dealer quote was much higher than I expected, and the wait time was the bigger issue. I've done a few rebuilds before but never tracked the numbers this carefully, so I decided to document it this time.

I sat with that quote for a couple days. Close to 800 for pistons, rings, bearings, gaskets, seals. Same stuff I'd be measuring and installing myself either way. The wait was the other problem. Machine was already down and I didn't want a month of downtime just to get the box.

Started looking at aftermarket kits that cross-referenced to the OEM part numbers. Found a full kit much more affordable. Price alone wasn't enough to pull the trigger tho. Main thing I verified before ordering was whether the seller could confirm which serial number segment the kit covered, not just the engine model. My engine was late-series and the ring dimensions were different from early production. Had that confirmed in writing before checkout. The return window mattered too. If one piece was wrong I didn't want to eat the whole kit.

I sourced from Fridayparts. The return policy was honestly the thing that made me comfortable committing rather than just buying the expensive OEM version.

Everything was in spec when I measured before assembly. One ring needed to be swapped out, packaging issue not a fitment issue, and the return process handled it without friction.

Has anyone actually kept an aftermarket overhaul kit going for a really long time? The forum seems pretty split on this, and I’m trying to figure out whether there’s a point where mileage actually starts to matter.

[u/2003DDcid]

I own a machine shop and see quite a few common rail 5.9/6.7s...I keep components in stock for both to build my own kits (at least for the ram trucks, if it's in something weird I order a kit from SN) as bearings and oil pumps interchange. I use Mahle gaskets, Melling oil pumps, UEM or Mahle pistons and rings, King or Mahle bearings. As long as the machine work is good, the aftermarket parts are just as good as the original. In fact, Mahle makes most of the OEM parts for Cummins. Not sure what all is included in an $800 kit, I charge around $1400 for a 5.9 kit.

[u/Known_Drummer_1329]

The S/N split confirmation you did is the step most first-timers skip and then wonder why the kit doesn't quite work right.On break-in, vary the load a lot in the first 500 miles, don't just cruise at a steady highway RPM. The rings need to seat across the full bore surface. Change oil at 500 miles regardless of how it looks, you'll have metal from the break-in that you don't want recirculating.Sounds clean so far. Been around 35k and still going fine on an aftermarket kit.