2018GMC

Search for voltage drop test on YouTube. My cable was replaced while under warranty. Cable looked fine but tested bad. I also checked all my grounds, cleaned them and no difference. My voltage will drop on long highway trips the eventually goes back to 14, but this is normal operation as the alternator is computer controlled.

Replace the negative battery cable. Mine had high resistance which was a common problem. That took care of 90% of my random “service stabilitrack” and other odd messages on startup. I’ve always had good voltage though.

I recently added this which greatly improved throttle response. I purchased this and the intake used as the new prices are ridiculous. https://afepower.com/afe-power-77-14003-sprint-booster-power-converter

Who do you recommend to have my truck tuned? I’ve used blackbear for my older trucks but they tell me they can’t tune the 8 speed transmission. I’d like to get both engine and transmission tuned. Truck is like new with only 24k on it and I purchased it new in 2018. I have a plug in AFM disabler but still use AFM on on long interstate trips. It’s always disabled around town though. 2018 GMC Sierra crew cab 6.5’ standard bed 4x4 max tow package 3:42 gearing 6.2L + 8L90. Completely stock except for stock muffler and flapper removed. Replaced with magnaflow 14909. Stock intake removed and replaced with AFE Momentum HD. https://afepower.com/afe-power-54-74104-momentum-gt-pro-5r-cold-air-intake-system Or should I just leave it alone? It occasionally tows my enclosed 4k lb trailer and max I’ve towed with it is 6k lbs. truck is rated at 11,700 lbs.

I may be purchasing a 1969 cst10 4x4 and have questions on a fair price and what to look for. What’s the most active form online for this generation off Chevy trucks?

Look for another frame in the years below. If you have a 1500 you need a 1500 frame 2500 3500 frames are different than 1500. 2007.5 - 2013 GMT900 generation 2014 - 2018 K2XX generation 2019 was last year and new gen as well but new T1XX generation 2019.5 - current? has a completely different frame. 2014-2018 K2XX generation may work as it was mostly sheet metal, interior redesign along with new powertrain offerings. There may be some slight frame differences but someone with more knowledge can chime in. I know when my buddy had a 2009 his frame looked extremely similar to my 2018.

I've read on other forums that a 33" overall diameter tire will fit. That is the largest that will fit in the spare tire location. These are all approximately a 33" overall diameter tire. 285/70/17 275/70/18 275/60/20 FYI - 17” wheel is the minimum that will clear the front brake calipers on 2007.5 - 2025 SUV and trucks. If you have the big brake kit (uncommon option) I believe 20” wheels minimum to clear the oversized front rotors that were offered as an option on RST trims.

23K miles on my 2018 sierra crew cab 6.6’ bed 4x4 6.2L 8L90. no, I haven’t been in prison for the last couple years or ever. I have multiple vehicles and might have a problem lol. Dealer replaced negative battery cable right before the bumper-to-bumper warranty was up due to occasional odd messages immediately after starting like service stabilitrack, Airbag, etc. Even after the negative battery cable was replaced due to it testing high on resistance. I still would see these messages messages occasionally right after start up. Replaced the battery. messages almost never show up although just when I think it’s really fixed I’ll get a message after a few months. Seems the only happen if I restart truck after a brief amount of time like after refueling. Engine and Transmission have been fine. I at home flushed the 8 speed with the new fluid at 18k miles. Drivers window rattles when closing the door. Only if it’s rolled up all the way. If I tap the down button just a touch then no rattle.

Videos of the suburban on my channel along with some other vehicles in the family fleet. DocTube - YouTube

Since you don't have the max tow package, your truck is probably 9200lbs since you have the 6 speed and 3:42 gears. My 2018 CC 6.5' bed 6.2 4x4 has the 8 speed and the max tow package with 3:42 gears. Normal gearing with 8L90 is 3:23. Max tow package and 6 speed you get 3:73 gears. My tow rating is 11,800. I wound never want to tow that much with a half ton. Like others have said, tow 75% or less of what it is rated for. If your truck is rated at 9200lbs it should tow 7000lbs ok, especially with a weight distribution hitch.

FYI - Best price for Mobil 1 Blue label Synthetic LV HP ATP 124715 $46.49 https://www.amazon.com/gp/product/B086R9GDV1 Make sure it is sold & shipped by amazon. I have ordered twice an both times received the blue label even though the product page pictures the old black label.

I hear ya. I changed the fluid myself, did the driveway flush and exchanged 12qts with the new blue label fluid. My 2018 only has 23K on it but I wanted to change out the factory fluid that can absorb moisture. I still get the odd clunky mixup shift every once in awhile in stop and go traffic but I’ve never had the shudder issue and don’t want to experience it.

@Grumpy Bear Thanks for the detailed explanation.

Anyone install the STL010 or updated GM transmission thermostat? I don’t want to do the pill flip because I live in an area where we get below freezing temps and 4 full seasons. Not sure if my 2018 8L90 has the updated part. It’s hard to read what number is stamped in the trans thermostat. my trans temps are always 180 - 200 during the summer and maybe got to 205 when crossing the desert with outside temps 115 - 118 https://static.nhtsa.gov/odi/tsbs/2021/MC-10207911-9999.pdf