On our '05 Yukon XL, I replaced all the rubber hose caliper lines with stainless steel braided lines at the 180K mile point. Brought back a nice hard pedal, no more 'ballooning' of the rubber hoses. It was a kit from Summit Racing.
I'm having the same issue with our 2015i Escalade ESV. Same tranny, 8L90E. It has had all the Field Action Recall items accomplished related to 8L90E shudder and driveability problems. But, it still hard shifts between 1st and 2nd under very light accelerator pedal push. If I 'lean' into it, punch it or we are towing, it shifts just fine. For background reference here are the service bulletins from 2015 related to this transmission: N150396 15396 HARSH SHIFTING WHEN STARTING IN LOW TEMPS - Corrective action was Trans Control Wiring Harness Replacement N150389 15389 TORQUE CONVERTER CLUTCH (TCC) SHUDDER - Corrective action was Trans module reprogram Then in 2018 the dealer performed 8480478 Flush and Drain fluids for Trans shake or shudder. Don't know if GM applied all these updates to 2017 models, but there is obviously a history with this transmission.
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Hey KC, I have an '05 Yukon XL with 5.3 flex-fuel. Volant cold air intake, Hedman shorty headers, original Y-pipe with cats, Flowmaster cat-back, never a single code. The drop-tube option with the Volant allows for airflow right from the bumper area to be 'pushed' into the air filter box, with this option I see MAF temps only a degree or two above outside ambient. My tuner is just a Bully Dog GT, I flash for premium when I'm towing, zero pinging with this timing and at least 91 octane fuel. 235K and counting... Enjoy!
Instead of the tow/haul button, I would manually shift to a lower gear that keeps the engine higher in the torque curve which would mean less shifting. I'm assuming you have the 5.3? Shift to a gear that keeps your RPM around 2000-2400 rpm, that minimizes shifting in your tranny, which keeps the transmission heat lower. Fuel economy will be a little less, but what's a few cents worth of fuel relative to the long life of the tranny. I'm at 230K on my '05 Yukon XL, original engine and 4L80E transmission. When I tow, it's always in 3 with tow/haul engaged.
Nice work! I also put MOOG upper and lower arms on my '05 Yukon XL 1500 4WD at about the 180,000 mile point about 3 years ago. Haven't had any issues yet and I'm passing 230,000 mi. Had both front hubs replaced much earlier, probably at the 130,000 mark, they were both humming a bit. BTW, this truck was assembled in Janesville, WI, many consider that assembly plant the last of the good ones.
If you have the 6.0 Denali, with the towing package, 7500 lbs is not a big deal. Owner's manual will have the actual recommended limit. Electronic brake controller is a must for the trailer brakes, and keep an eye on tranny temps. We tow 7000 lbs with 05 Yukon Xl with a 5.3. Your Denali can most likely handle 9500 lbs. properly set up and handled.
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