Paging DirtyLarry, roommate bought an 8.1 Yukon XL

[83GMCK2500]

Also, anyone else with vast 8.1 experience. I searched the limited 8.1 threads we have around here and I didn't quite have all my questions answered, would appreciate your input on maintenance items, recommended service.

My roommate (Ted) has a '97 K2500 EC/LB 454/NV-4500 truck that he uses to tow his TT around in the summer on camping trips. Recent addition to the family (up to 4 now) dictated it was time to find a larger tow vehicle. Found:

2001 GMC Yukon XL 2500 4x4, 8.1L, 4.10/G80, 192k miles (Ted subscribes to the "no replacement for displacement" theory)

I went and looked at it with him, usual seat wear, couple small dents, overall really clean and well taken care of. Hadn't been started in weeks (supposedly) and it was cold when he started it up while I had my head underhood. There was the slightest valvetrain noise that almost totally clears up after short while. I crawled under it and there is a loose heat shield, that's it. The rear axle seals are clean, pinion and ends; transfer case outputs are clean; front axle is clean...it's really quite impressive. The only wet spots are steering lines and engine oil cooler lines. The trans fluid still had enough red to it and didn't have any unpleasant odor, I know the 80/85E is far more robust than the 60/65E found in 1500s.

The person Ted bought it from has had it since 163k miles, in that time he's done engine oil changes, a radio install, and the driver door window regulator. That's all he could remember.

Other observations: once it's warm it has a random miss, brake fluid is black, power steering fluid is dark, under very light load and a medium coast the rear end has a slight whine.

What we've got on the list so far:

- Plugs & wires (already ordered oem delco sets for both)
- Seafoam the intake and half can in the fuel tank. It's due for an oil change, do that after seafoam.
- Check/replace air filter, replace fuel filter, check/replace cabin filter
- Trans filter and fluid (not full flush, just the qty required to do filter).
- Transfer case oil change
- Front and rear diff oil change
- Would like to talk him into power steering fluid flush and brake fluid flush.

In the past I've had good results putting ~1/3-1/2 can of seafoam in the engine oil when it's warm, running it a short while and then doing an oil change. I've also read where some people use ATF and the detergents in there accomplish the same thing only more gently. Yay/nay/waste? If the tuneup doesn't clear up the random missfire there is a good injector service shop in the area that disassembles, ultrasonically cleans, puts new screens, seals, etc as part of a complete injector service.

Anything we haven't though of? The two 8.1s my dad had were 1) half the miles and 2) ordered brand new. This is the first higher mile one I've been around, but I've got 305k on my '96 now so not unfamiliar with high mile big blocks. What do you recommend for engine oil, brand/weight? I run Shell Rotella T 10W-30 in my 454. Ted hasn't had this one long enough to determine how much it uses at what interval, but I warned him that is a "feature" of the 8.1.

Thank you for any advice you might have, onto the pics.





P.S. The last L29/L18 advice you imparted upon me was here: Post 27 and just wanted to update that I found brand new L21 valve covers and the correct ECM bracket to retain the 12200411 ECM under my GMT-400 hood. The one found in 2002 3500HD chassis-cabs...had to special order them, so I ordered 10 and will be selling the extra for the increasingly common 411 ECM swap.