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

I have a 2003 suburban z71 with factory 6 disc in dash cd receiver. When it’s colder than 50 degrees the radio powers on but now sound or door chime until the cabin warms up. Summer months it works fine. Cold months nothing the you hear a pop and you get sound. I’ve tried replacing the Bose amp (under the center console) pulled from a junkyard Tahoe of same vintage. Still same issue. Also tried reflowing solider in the main circuit board on the radio receiver and my original amp. Still no change has the no sound when cold. The random theftlock seems new but it self heals and goes away within a few seconds. Only happens very rarely. The random radio powering off then on is new. Anyone else experience this? Is there a known wiring harness issue under dash or center console? My burb has the sunroof, maybe in the past 20 years someone left it open and it rained? Although switching out the Bose amp didn’t seem to fix anything. Also get codes Radio DTCs U1000 Class 2 Data Link Malfunction U1016 Lost Communication with Powertrain Control Module U1151 Loss of VIU Communications U1167 Lost Communications with Rear Seat Audio/Rear HVAC BCM DTCs U1000 Class 2 Data Link Malfunction

I usually run bilstein 4600 for stock height trucks. Recently put KYB monomax on 03 suburban they are 1” shorter than stock which may be ideal for you. I had to add a 1” spacer to the fronts to get full suspension travel. Monomax ride is noticeably firmer than bilstein 4600 but not harsh. Helps firm the old burb up.

I sent the engine computer to Blackbear performance and they put their 87/89 tune on. I left the tow haul button alone since I occasionally tow 3500lb enclosed trailer. After the tune there is more getup and go, trans shifts are firmer and it revs out a bit more over stock, like 5600 / 5700 rpm. Apparently they have a high octane tune for max performance but I didnt opt for that since I don't want to put premium in all the time and its a big heavy suburban after all lol. After the tune, maybe I gained the 10 hp the later engines were advertised with. I live at 7k foot elevation so there aren't any dyno places by me but with the tune, afe intake, and magnaflow muffler, i've done the "easy" performance upgrades.

Took all day to cool down to 110 but on a level surface, idileing in park, i drained half a quart out of the 10mm check plug. I put the plug back in when the stream slowed to a thin stream / spotty trickle. Should I leave battery disconnected overnight or a few hours since I put the new fluid in? Does this reset the transmission shift learning? I don't have shudder issues but I do have the occasional lurch in park when cold and sometimes harsh engagement when shifting into drive or reverse. Very cold winter temps there is the rubber band feeling when accelerating from a stop but once engine and trans warm up no issue. Summer driving and towing no issues.

Propane torch on the surrounding area and hammer the side. Not sure if you are in the rust belt but heat and hammering the side not directly on the ball joint is what helped me. Sounds like yours may be heavily rusted and now one part. Try a different penetrating oil like Deep Creep. Deep Creep | Premium Penetrating Oil & Lubricant for Shop & Household (seafoamworks.com)

I posted this question on TahoeYukonForum, no one had a definate answer but the two theroies were. 1.The switch to electric fans from mechanical. along with more powerful P59 Engine Computer. 2.The LM7 did not have a separate high and low octane table in the tuning. The L59's high octane table had more aggressive timing......and that is where the power increase is from. But only if it determined you put premium in it (it determines this by not hearing any knock while trying to run the most timing it can get away with)

My internet research points out: LM7 isn’t flex fuel compatible and that’s the main difference between LM7 and L59 according to multiple posts. They are 99% the same. I realized this past weekend that I've had an L59 the whole time I thought it was an LM7. Only differences are more injector flow (33 lb/hr vs 22.5-28, depending on the year iirc), different fuel injector connectors (EV6, I believe, vs minitimer), and a few differences in the ECU. Depending on the year, it got a sensor to detect the ethanol content of the fuel, and also depending on the year, it kept return rails longer than the non-flex fuel motors did. Besides that, it is literally the exact same motor. https://rxmechanic.com/l59-vs-lm7/ L59 Vs. LM7 Engine : What’re the Differences? | Rx Mechanic The factory L59 injectors were rated at 33-36 lbs. and support about 435 hp at the wheels. Note the 2001-04 return style fuel system cam with 33lb injectors running at 50 psi, while the 2005-07 engines were returnless and had 36.6lb @ 58psi injectors. The easy way to know which you have is the 2002-04 rails were plastic and the 2005-07 rails were stainless. https://www.onallcylinders.com/2018/10/12/l59-5-3l-engine-upgrade-guide-expert-advice-l59-mods-maximize-performance/

Anyone know what the difference is between these two generations? What was changed on the later versions to increase +10hp and +5tq. Intake? Cam? Just the tune? I have an 03 Burban early build with 8th digit T = LM7 so I got the 285hp LM7. I did get it blackbear tuned which definitely woke it up. 2000 - 2003 285 hp@ 5200 rpm 325 tq @ 4000 rpm 2004 - 2006 295 hp @ 5200 rpm 330 tq @ 4000 rpm

I've done all the work myself except for the alignment and enjoyed most of it. Everything seems good now except I dont get sound from speakers when temps are cold 40F and below (no chime or radio even though radio turns on) After the interior warms up you hear a pop and sound works as it should. This summer it hasn't missed a beat. I replaced the bose amp under the center console but issue still persists. Tried replacing the head unit with another one from junkyard but found out about theftlock. The few places I find on ebay and internet say they don't reprogram bose radios. I may try reflowing solider with a heat gun on the original head unit. Front bumper needs a repaint (tons of rock chips) Rear bumper needs replaced (dented) Of course all the bumpers i find in junk yard are usually beat to hell or not the z71 version. Also a meguiars M105 / M205 cut and polish. Unfortunately it has some deep pin striping down the side but it looks great 15ft away lol. A lot of this gen I see around has severe paint fade and peeling. So far this pewter has held up very well for 20 year old paint. Performance upgrades: Blackbear tune Magnaflow 12588 performance muffler AFE cold air intake.

Wasn’t looking for a suburban but a friend wanted it gone and the price was too good to say no. He did basic maintenance but it needed a lot to make it road trip ready. It has 170k on engine. Transmission was replaced 15k miles ago. He only put 22k miles on it in 10 years of ownership. Things I’ve done: -Multiple degreases and pressure washing engine bay and underneath. -Valve cover gaskets -All 4 O2 sensors (Denso brand) -Exhaust gaskets and Felpro bolts. Had to use Dorman fix on driver side rear bolt was broke off flush. But now no ticks when cold or hot. -Main and ac serpentine belt -Upper and lower large radiator hoses -Torsion bar bushings and new 2” lift torsion keys -1.5" rear coil spring spacers -kyb monomax shocks all around. -Alignment -Intermediate shaft and lower steering column bearing -All 4 window regulators -Fuel pump with sender. Installed Flex fuel pump since it had "robust fuel level sender". Had to change flat 4 plug to square 4 plug but it dropped right in my vin T which is LM7 5.3 non-flex. -Front diff fluid (terrible dirty, prob original) -Rear diff fluid (not bad was changed 10 years ago) -Autotrac transfercase fluid (the special blue Fluid (looked good was changed 10yr ago) -At home trans flush to maxlife synthetic atf. Disconnected trans cooler line at radiator and pumped fluid till new came out. Also dropped pan and new filter. Fluid looked pretty good, some grey clutch material in bottom of pan and on magnet but pretty minimal. -power steering flush -engine oil -Carpet cleaning -Steering wheel buttons (lights were out) -rear hvac actuator. (was stuck on ac (blend door actuator) -Driver heated seat bottom and back new heating elements -spark plugs and wires. Plugs I pulled out had ngk and part # on one side but acdelco and part # on other side. Thought they were counterfeit but sent pics to ngk they said they were oem plugs, could be original at 170k -Front Brake pads, Rear Brake pads, Parking Brake shoes. -Greased all fittings -sway bar links -Z71 factory running boards -Denali cluster with trans temp gauge -Idler and pitman arms were replaced 20k miles and 8yr ago. I've now put about 2k miles on it and it hasn't missed a beat. The blackbear tune made the biggest difference in seat of the pants feel. Also firmed up trans shifts. Towing my 3500lb enclosed trailer, it doesn't do as well as my 97 k1500 with 5.7 also blackbear tuned. Both are 3:73 gears. But the 5.3 does alright just has to downshift and rev sooner than the 5.7.