YYC-SIERRA

Thanks guys. I'm going to rotate the tires and see if it changes.

I'm at 90k, just put new AT tires on this spring. Started getting a light drone / hum noise in the front. Can't tell if it's just my AT tires or a bearing going out. Tends to slightly decrease the drone / hum in a right turn, stays constant during straight driving and left turns.

What age / mileage do the bearings typically start to go on these 14-18 trucks? Is there one side bearing that typically goes first? (had an old subaru, it was always right rear)

I just installed new Sumitomo AT tires a few weeks ago. Did a 500 mile roadtrip, pretty pleased with the quiet smooth ride. If you're looking for an AT tire, these are tied with BFG KO and Toyo AT3 for best in category on Tire Rack. They're significantly cheaper. I got my 265/70/18s for $171 each, plus shipping, from Discount Tire Zone. All-in price was $768 delivered. https://www.tirerack.com/tires/sumitomo-encounter-at It's a Japanese company that also includes Dunlop & Falken. My tires were manufactured in Thailand.

I found what I was looking for: Fuel Pump Insulator - GM (12695634) Question: Does anyone have first hand experience running their intake manifold with and without this rubber/foam insulator? How much difference does it make to the sound?

Thanks very much for confirming that. It appears there is no equivalent part from the L83 manifold.

I have an S&B CAI paired with the L86 throttle body & manifold upgrade...plus a stage 2 BTR cam. At below 2000rpm in 5th or 6th on the highway, the intake noise is egregious when going up any incline. Really raspy, vibrates my overhead plastic panel, sounds like its lugging.....but the actual power output is fine. I'm hoping by adding this missing insulator, it'll reduce the noise. Above 2000rpm in 4th, 3rd. 2nd it sounds amazing!

Does anyone have a part number for the insulator from a 6.2 L86 intake manifold. The rubber insert to help reduce noise. My new L86 manifold I ordered from rockauto didn't include this noise insulator. Do the L86 even have them? My L83 manifold I replaced definitely had one. (Picture for reference but not sure if it's an L86)

I can't believe it took me this long to figure this out. I didn't even know that valve was there till last week. The chirping noise has been eating at me for over a year. I thought it was my camshaft from a lifter failure.

is it possible it's your adaptive exhaust valve? Go underneath and move it by hand, see if it makes the chirping noise. I just secured mine today and it was 100% that noise I've been dealing with for over a year. https://www.gm-trucks.com/forums/topic/266667-squeaking-underneath-truck-solved/

Just rotate the valve all the way CCW and secure it from moving. That's it. If you ever want to reverse the mod, just take off the screw or clamp. This is a MUST DO in my opinion if you deleted AFM and run in V8 full-time.

Have you ever heard that metal squeaking / chirping sound from under your truck, kind of sounds like a chipmunk? It's most likely your adaptive exhaust valve. The valve is spring loaded closed, and opens during the transition from V4/V8 from exhaust pressure. Eventually they wear out and get rusty and start squeaking like crazy. They're easy to disable (lock fully open) with a screw or clamp, clothes hangar etc. Whatever you prefer. I used a clothes hangar today and the difference was instantly noticeable. ZERO metal noise, no squeaking, the exhaust actually sounded calmer at idle. Best of all, my idle smoothed out tremendously (AFM delete with stage 2 cam upgrade). I was experiencing sporadic rough idle during city driving. I just thought it was due to my cam upgrade since big cams aren't designed for smooth idling. Turns out, when we did the AFM delete, we should have disabled the adaptive valve!! It's SO much better now.

No kits per se, but it's easy to piece together: Derale 13005 filter mount --- just attach it to your frame ahead of the engine with the supplied screws (drill a pilot hole first) https://www.summitracing.com/parts/der-13005 Grab a Wix 51269 (or Napa 1269) fluid power filter / hydraulic filter https://www.rockauto.com/en/parts/wix,51269,filter,8600 That's basically it......just need a few feet of 3/8 oil cooler hose from your local auto parts store, a few worm clamps and 2 heater hose connectors --- put it all together and you're good to go. https://www.oreillyauto.com/detail/c/gates/air-conditioning---heating/heater-fittings--universal-/c93f37b5f9fc/gates-3-8-inch-straight-hose-connector/gat0/28602

Yes I flipped the pill 3 years ago so the trans thermostat has been in bypass ever since. I also installed a remote transmission mount and run Wix 51269 hydraullic filters downstream of the radiator on the transmission return line. Now combined with my upgraded Circle D converter and Tru-Cool 40k, I aim to have the world's 1st million mile 6L80e without failure, lol