Just bought a 2015 Denali. It’s got 77k miles. Not sure what all has been done previously as far as maintenance and updates. What should I be looking for or what should I be checking that may need changed or looked at?
If it hasn't had a transmission flush, Severe schedule change is set at 45k miles. Also coolant is at 5years. Brake flush I think would have also been recommended. For me, the transmission would be #1. 77k miles, you are still good to get it flushed, you will find a bunch of ideas on drain and fill vs. flush. As long as you keep up on the maintenance (77k miles is fine), flushing is typically fine, its the vehicles with like 300k (exaggeration) miles that have barely gotten it's windshield fluid refilled that you might think twice about a flush due to all the junk that's probably stuck and needs to stay stuck. If you don't have maintenance records, I'd just make a list from the owners manual and list them in order of what you feel is most important and work on getting everything done. Another thing our owners manual recommends is using dielectric grease on the door seal/weather strip, (GM part #12345579). If you opt to do that, don't use too much. I think 5 years was kind of the point where I was getting a bunch done. But I did a bunch all at once because I was either slightly over due or it was coming up. I'm original owner, after I got it all serviced, thing drove like the day I drove it off the lot. I'd also give it a fresh paint detail depending on if you think it was done before you bought it.
Try to get a GMVIS report from a local GM dealer. That report will (should) have a history of everything done to the vehicle at a GM dealership. That can help with deciding what needs to be done with respect to recalls, campaigns, and regular service items.