At 131000k, alone with the obvious Oil and fuel filter change, I would assume the Rear Diff, Front Diff, Transfer case and Coolant have never been changed and do them right away. Setup a good baseline for yourself. Have the trans flushed too if there no service record for it. (basically all the fluids haha)
- Rear diff - I would put in full synthetic, 75W-90 or even a 140 if you live in real hot climate and tow heavy.
- Coolant - Unless it looks super clean or you have a service record for the change, I would do a thermostat (OEM only), new coolant, possibly new hoses.
- PS fluid - bare minimum I would use a turkey baster to suck out as much fluid as I can then fill, drive repeat 2-3 times. If not a full flush.
- Brake fluid - I would just change it all the first time I did the brakes.
- valve lash - thats coming up at 150k, its pretty simple but take a while the first time if you have not done it before. google-fu!
- CCV Filter - Check to see if you still have one, if it was "deleted" I would likely buy a new one and put it back. This should be changed every 67,500k, but I would do less, like 50k.
Heres a good link on the service intervals
, fluid quantity, fluid types and parts: 6.7L Cummins Maintenance Schedule & Service Information
As for the deletes, thats good you are deleted but you pretty much must have a tune on the truck to be deleted. If you didn't you would be in limp mode with CEL. Now they could have used a "stock HP/Tq" tune, but more than likely you its something mild for better MPG. Not many spend the money on a tuner to delete and don't bump the timing a notch to give better efficiency. Nothing to really worry about, but just be away it is likely tuned, even if a stock tune, and it is federally illegal.
Trans - Saving up for one or not, IDK, I see plenty of guys getting 200+ on the stock trans. It all in how you (and the PO) treat it. No burnouts or WOT until 1800rpm and new fluids at or before intervals goes a long way. As does minding the temps, Even on stock truck I would put a trans temp gauge on it. Personally I would get a ISSPRO EV2 trans gauge from Genos, it will come with a clip thingy that holds the temp sensor right up on the steel hot line out of the trans. This is a great place to read temps form and does not involve cutting the line. Pickup a SRT10 pillar to mount the gauge! unless you plan on adding more gauges that is. But trans temp is a minimum.
Other than that, drive the piss out of and you will learn what it needs. 130k is nothing, its mostly catching up on maintenance that was likely skipped, and undoing stupid mods like CCV filter delete, or random electrical crap people feel the need to do a shotty job at lol.
EDIT: Heres my maintenance log if you want to take a look, Its a work in progress but I try to get everything I do on it. (some equipment came off, but thats not on the sheet)