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Hope nobody minds, but I'm going to start up a Quick Reference Guide for common parts/fluids/bulbs for the T1 HD trucks. I'll try to keep it updated if anything changes. If a mod wants to sticky it, I'm down for that too. Owners Manuals Chevrolet: https://my.chevrolet.com/content/dam/gmownercenter/gmna/dynamic/manuals/2020/chevrolet/silverado-2500-3500/2020-chevrolet-silverado-owners-manual.pdf GMC: https://my.gmc.com/content/dam/gmownercenter/gmna/dynamic/manuals/2020/gmc/sierra-2500-3500/2020-gmc-sierra-owners-manual.pdf Diesel Supplement: https://my.chevrolet.com/content/dam/gmownercenter/gmna/dynamic/manuals/2020/chevrolet/multimodel/2020-6.6-duramax-diesel-supplement.pdf Oil Changes 6.6 gas L8T (VIN code "7") Capacity: 8 Quarts AC Delco Oil Filter: PF63E / 19383806 Drain Plug Size: 12X1.75X18.15 6.6 Diesel L5P (VIN code "Y") Capacity: 10 Quarts AC Delco Oil Filter: PF26 / 89017527 Drain Plug Size: 12X1.75X18.15 Engine Air Filters 6.6 Gas: A3244C / 84121219 6.6 Diesel: A3248C / 84554703 Engine Fuel Filter 6.6 Diesel L5P: TP1015 / 23304096 Interior Filters Passenger Compartment Air Filter: CF185 / 13508023 Wiper Blades Drivers & Passenger Sides: 23387857 Spark Plugs 6.6 Gas L8T: 41-114 / 12622441 Glow Plugs 6.6 Diesel L5P: 68G / 12690238 Fuel Tank Sizes 6.6 Gas L8T, All Box/Cab Configurations: 36 Gallons 6.6 Diesel L5P Double Cab Long Box/Crew Cab Standard and Long Box Configurations: 36 Gallons. 6.6 Diesel L5P Double Cab Standard Box Configuration: 29 Gallons. 6.6 Diesel L5P Regular Cab Long Box Configuration: 28 Gallons. Diesel Exhaust Fluid Tank Capacity: 7 gallons Automatic Transmission Fluid 6L90 6 Speed MYD (Gas engine): DEXRON-VI Automatic Transmission Fluid 10L1000 10 Speed MGM/MGU (Diesel engine): DEXRON ULV Automatic Transmission Fluid. Transmission Capacities (Approximate): 6L90 6 Speed MYD (Gas engine) Pan Drop: 6.0 quarts Overhaul: 10.5 quarts Complete System: 12.4 quarts 10L1000 10 Speed MGM/MGU (Diesel engine) Overhual: 20.6 quarts Complete System: 22.08 quarts Transfer Case Fluid Electronic Shift Non-Autotrac MP 1625/1626–NQF: Dexron VI Electronic Shift Autotrac MP 3025–NQH: Dexron VI Transfer Case Fluid Capacities Electronic Shift Non-Autotrac MP 1625/1626–NQF: 2.4 Quarts Electronic Shift Autotrac MP 3025–NQH: 1.6 Quarts Brake System Hydraulic Brake System (Vehicles with DOT 3 brake fluid): DOT 3 Hydraulic Brake Fluid Hydraulic Brake System (Vehicles with DOT 4 brake fluid): DOT 4 Hydraulic Brake Fluid Wheel Lug Nut Torque All Models: 140 lb-ft / 190 N-m Front Axle 9.25" Axle Lubricant: 75w85 Synthetic High Efficiency Lubricant, 10-4091 / 19300457 Capacity: 1.9 Quarts Rear Axle 11.5" Axle Lubricant:75w90 Synthetic Lubricant, 10-4016 / 88900401 Capacity: 3.17 Quarts Rear Axle 12.0" Axle Lubricant:75w90 Synthetic Lubricant, 10-4016 / 88900401 Capacity: 3.17 Quarts

I am looking to replace my sensor and the harness as they are known to be bad and causing the p0711 code. In my research I found the 2015 has a split harness but they changed it in 2016 to a one piece harness and then I believe they went back to the split one, not sure which year. What is the part number for the sensor and harness? I've looked everywhere and can't find nothing, plenty of threads but noone has mentioned part numbers and acdelco website does not have a part listed in their catalog for that year.. nor does any parts site like napa or autozone

Just curious if anyone has the same issue I've been having. So on the very first shift of the day from 3-4 my trans seems to slip into gear. After the initial run through the gears it shifts great every single time after that. I have real basic stuff done to my 14 Sierra..cold air intake, cat back exhaust and blackbear tune (yes the trans was tuned). It really seems to be temperature related because it gradually got worse the colder the nights get (I live in the northeast). And no matter how long I let the truck warm up before I drive it, it does the slip but only 1 time. Not sure if this is also related but the tuner said the torque converter locks after the shift into 4th gear.

Has anyone else used the AMSOIL OE ATF over the Signature Series in their 8 Speed? Any issues? Looking to get a flush done soon and want to make sure the fluid is compatible. I'd rather not shell out $300 CAD for the signature series when the OE will do. Thanks.

Hey all, 2017 Silverado, 5.3/6spd. My transmission issue only happens when I first drive the truck for the first time in the morning. The truck has to have been sitting overnight for this to occur. After starting the truck and driving, the trans will "fish bite" or stutter when shifting from third to fourth. It will do this once, (maybe twice) and be good and problem free for the rest of the day. Has anyone else experienced this? It only happens when the truck is first driven after sitting overnight. It's not really a major issue, as it doesn't happen again after the first time, but it's pretty annoying. This issue only occurs at light/part throttle, and my speed is around 25-30 mph. I do not notice any variances on the tach while this happens. Also, if I drive with more pedal/throttle, I will not experience this stutter. I spoke with the dealer about this when I went in for my second free oil change, and they could not replicate the issue. During my first trip to the dealer, they downloaded a program update for the transmission. It helped overall, but the isolated problem is still present in the morning. I have read somewhere on this forum, that this was a "normal" occurance, and attempts to remedy should not be attempted. I believe that post mentioned that transmission fluid temperature played some part in this. Any ideas or input? Thanks in advance! Steve

Hi All, Newbie here in the forum.. Vehicle: 2021 GMC Sierra 1500 Denali I took the truck to the shop for 3.5 inch lift, earlier. The guy who works there said if I lift my truck, GMC is going to void my entire warranty. I wonder if this is normal? I was also told that most of the lifted trucks have transmission oil leaking issues, so I will need to install a front differential drop kit. Does GMC has such issue for only 3.5 lift? Thank you guys in advance!

So up until yesterday the truck was driving relatively smoothly, there was the occasional hard shift from 1st to 2nd (which I believe these trucks are known for). I stopped at a stop light yesterday and started going and then at about 20 MPH the truck decided it didnt want to shift. This happened a few times throughout the day and seemed to get worse as the day went on and at this point it now does it every time it gets down into the lower gears. I switched to manual to see what gear it was stuck in and it showed 2nd and then 3rd after it shifted and didnt want to shift up. EDIT: Transmission temps when I was looking did not appear to get above 205 F, Fluid is red like it should be, level seems fine. Is there a known issue with these transmissions or an easy fix I can attempt? Transmissions are voodoo to me

I have a 2019 Silverado LD with 21k miles on it. I noticed that if I'm in manual mode, I get a hard downshift from 3-2. No other gears. It does it off and on. What could it be?

Bear with me, this is a long post, but I've been troubleshooting a bizarre intermittent transmission slipping issue and potentially a related electrical issue. Any thoughts/theories would really help here. Just to note, the two shops, Shop A and Transmission Shop B have a reasonable reputation in my area. Vehicle: 2004 Silverado LS 1500 4x4 Ext Cab Short Bed, 111,000 miles (daily driver until 2016), 3,000 miles/year since then. Owned since new, this truck has not lived a super hard life. Symptoms: 1) Initially had intermittent slipping in 1st gear, either in DRIVE or manual gear selection in middle of June 2) Continued to slip intermittently after transmission fluid/filter replaced July 6th 3) Check engine light (code P0758 ONLY) appeared late August, would not go into 4th in DRIVE and slipping in 1st gear again (in both DRIVE or manually selected). 3rd gear on highway works fine. Manual selection of 2nd and 3rd seems to be okay to get around. 4) Solenoids A and B replaced by Transmission Shop B on Sept 3rd 5) No obvious power drains EXCEPT on the IPC/DIC circuit which was about 200 milliamps 6) Previous battery draw issue over the previous 2 years. Usually would kill a battery between 12 and 48 hours. Very intermittent issue. 7) Recent wet day battery draw issue reappeared. Actions taken so far: 1) Fluid and filter replaced by Shop A on July 6th a. Worked for one week, slipping issue reappeared intermittently throughout August 2) Solenoids A and B replaced by Transmission Shop B on Sept 3rd and solenoids tested with independent power source, functioning properly. a. No change, Check Engine Light still illuminated with code P0758 3) Checked all fused circuits on Sept 4th a. One drain on the IPC/DIC circuit of about 200 milliamps Working theories (in levels of severity): 1) Possible gauge assembly short due to the IPC/DIC circuit drain possibly related to a transmission control circuit? Seen this pop up a few times on other forums, but I am doubtful, then again, this was early 00's GM where fog light fuses did not match with the fog light circuits... 2) Short on the transmission harness 3) Short between the PCM/ECU unit in the engine bay and the transmission harness 4) Bad PCM/ECU unit <-- This is my top theory considering the connectors are oriented sideways and have dirt/debris all over, combined with a wet day may result in a small short causing both the transmission issue AND the battery draw.

After accelerating in sand up hill my traction control light kicked on, I attempted to override by pushing the TC button and lost all forward motion immediately. Reverse engages and I can also lock 4wd in reverse however no forward gear or forward movement at all. i dropped the transmission plate with no metal shavings and oil looked normal. Next I changed the separator plate with new check balls in the valve body. New filter and fluid with same result…any suggestions I’d appreciate. Not once did I hear any grinding and no codes were given on the dash. All shops want to buy a new transmission rather than trouble shooting. Please help.

My 09 silverado 5.3 4x4 has shifted hard into 2nd and some into 3rd for several years now. A few months ago I decided to fix it. Codes were for transmission control solenoids, module, oil pressure sensor, misfires...etc. codes like P0700 P0717 P0521 P0523. I replaced all 3 shift solenoids, oil pressure sensor, and immediately the truck shifted like new again and it lasted for a few days or a week. And it started shifting hard again. Really hard. It's so frustrating. And it's throwing all the same codes again. Recently, my truck started misfiring so badly the entire truck was shaking. It was running on two cylinders. All of the ignition colis were failing all at once and the truck was not drivable. Btw, I just changed out those ignition coils, plugs and wires just two years ago, all Ac Delco plugs/wires and duralast ignition coils. So anyways, I replaced all of the coils plugs and wires again this week and the engine no longer misfires, running on all cylinders again. And for a few hours after, there was zero hard shifting now. It was running great, like new again. Shifting smooth as could be. But after making it into the city and hitting traffic lights and stop signs, it didn't take long for the very hard shifts to come back. I've read on this and have been dealing with this in time and parts for so long now. I've read about ground wires could be the cause of all of this. I have replaced everything the computer has suggested, and for a short time after the repairs, the truck would run like new. But the hard shift always comes back. I know there's people out there that have had this same problem. I've read a lot about it but without actually finding the grounds for these specific sensors, I've hit a dead end. The issue just keeps coming back as it's obvious there is a root cause I am not getting to. Please share any knowledge or experiences on this topic. And any knowledge of the location of these grounds may be at. Thank you!

Please Help. We're working on a 2001 Chevy Silverado 2500HD.It was stuck in limp mode. We first got the P0783-85 codes, so we replaced both shift solenoids, as well as the wiring harness. Still shot the same codes and was stuck in limp mode. So we replaced the transmission. Still didn't work. Now it's pulling up P1860 and both shift solenoid again. Also I realized it was shooting these codes before I even put it in gear. And that's what makes me think it's the ignition switch. Any help at all will be greatly appreciated and save my sanity.

I have a 2017 GMC Sierra 1500 Denali 6.2L with the 8 speed transmission (73,000 miles). When shifting from park to drive/reverse there is a clunk and also when the truck is accelerating from low RPMs there’s a hard shift from 1-2 & 2-3 gear. I’ve taken it to the dealer multiple times and they “can’t find an issue” with it. Any help would be greatly appreciated! IMG_6286.MOV

Sorry if this seems long winded but I want to provide as much info as possible. Just picked up a 2019 Silverado 1500 custom. Has the 4.3 V6 with the 6 speed transmission (6L80 I believe) The truck had 99 miles on it. Currently around 2500. No issues out of the gate, after about a week of driving I noticed a very delayed shift I think it was from 1-2 or 2-3. The engine revved 1-2k high RPM than normal before shifting. a few days later while on the highway (cruise set at 75mph) out of no where the RPM’s spiked as if it had downshifted. There was no additional load on the engine to cause this, like going up or down a hill. This happened a few times. I called the dealership immediately and brought the truck to them a few hours later. Got a loaner for a few days while they looked over it. They called me to come pick it up, said the tech noticed a little bit of rough shifting and said they “re-set” the shifting points. Since it was an intermittent problem for me I don’t think it arose for them. So I took the truck home, no problems. My wife drove it to work that same night and the same problem happened again. This time the engine light came on. I scanned the codes this morning and the ECM showed P0700 (transmission control system the TCM showed P2714 pressure control solenoid D performance/stuck off. So back to the dealer it goes, waiting for them to bring me a loaner this time. I was was told by a dealer technician that GM has been having them put a different type of transmission fluid in some of these trucks due to issues with the torque converter. But I guess if a solenoid is stuck it could be due to a fluid issue as well? Just speculating. I’m curious if anyone else has had similar issues. I haven’t had much luck finding anyone else online with the same problem. Which is guess is more of the reason I’m posting this, in case there’s someone else lost like myself. I will keep this updated when I get further down the road with the dealership. I get that there are fluke problems that can arise, but this is a bit irritating considering it’s a brand new vehicle. I will say that the dealership I’m working with has been extremely supportive and not trying down play anything I’m complaining about.

Hello everyone, Well I took my 2014 Chevy Silverado 1500 up to the dealership yesterday for transmission issues. When accelerating around 30mph the transmission makes a high whining noise around 2000 rpm almost like its slipping and the truck shakes back and forth. Then when on the interstate on cruise control around 65-70 you will hear a grinding noise every few minutes. Also when you slow down from the 60-70 mph range to around 30 mph and accelerate the grinding noise becomes more apparent. When I dropped the truck off yesterday I showed the service guy video of the grinding as well as what I believe to be slipping and he said "Yeah that sounds like it is slipping". Received a phone call this morning from the same service technician saying they were not able to replicate the issue. That the transmission guy said that is normal when it switched between V4 and V8 mode. It's amazing I have had this truck and driven it for 76000 plus miles and have never heard that whining or grind noise. I asked how long they test drove it and he said 10 minutes. I told him they need to drive it around longer and actually go on the interstate to hear and see what it is doing. This is not the first time I've taken my truck up there for transmission problems and I am not picking this truck up again until they find the issue. The first time was for rough shifting to which they said was normal. This is my first Chevy I ever have bought or owned. Bought it brand new from the dealer. I must say that with how I keep getting treated with the "can not replicate" issue as a scapegoat for not truly trying to satisfy the customer is getting old. Especially being I have videos in which you can see the rpms and hear the whine up and hear a grind noise. This will most likely be the last Chevy product I purchase. If anyone has any ideas and doesn't mind listening to the videos I have I would appreciate it. I will have to post a link to youtube since the video will be to big to post here. Thanks

I have a 2017 GMC Sierra 1500 Denali 6.2L with the 8 speed transmission (73,000 miles). When shifting from park to drive/reverse there is a clunk and also when the truck is accelerating from low RPMs there’s a hard shift from 1-2 & 2-3 gear. I’ve taken it to the dealer multiple times and they “can’t find an issue” with it. Any help would be greatly appreciated! IMG_6286.MOV

Anyone have a check engine light show up then go away and come back? Code uo129 lost communication with brake control module, UO101 lost communication with transmission Control Module. Went to bed with no check engine light, woke up in the morning for work and noticed the truck would not remote start. When I go in to head to work noticed check engine light. After work ran codes. Shortly after getting codes and using google to research check engine light was gone. Went for a drive never came back on. Woke up this morning it was on again. Can anybody relate?

Recently bought a 2014 Silverado LT w/ 5,3L and 6-speed trans(4wd crew). Truck has 110,000 miles on it, but appears to be lightly used and truely all highway miles. I have been driving it for a week now w/ no issues but this morning on the way to work under light driving the truck jerked and the engine light and the traction control light came on. They went off about a mile down the road but truck now seems to shift hard. Is this a sign of transmission problmes? Should the dealer have been able to see this problem by reading recent codes? I was told there were no issues and the truck had just been scanned and had no codes in the record. Any ideas on the problem? Any comments on if i got screwed by the dealer? Are there issues w/ this transmission? What should i be doing to remedy or extend the life of the trans? Any thoughts would be appreciated. Thanks I have a 2007 that has shifted ereatically from day 1 and now has 180,000 miles without a failure, maybe chevys just shift this way?? ughhh.....

John Goreham Contributing Writer, GM-Trucks.com 4-25-2019 Back in December, GM-Trucks.com member Jammin87SS posted a note here about a class-action suit related to GM 8-speed automatic transmissions. This transmission was used widely by GM, including in the Sierra, Silverado, Colorado, and Canyon pickup trucks. Owners have been complaining of shuddering and hesitation. Owner of a Silverado, Ed T., wrote a typical description for CarComplaints. He says, "Ever since I bought this truck new there has always been a shifting problem. This problem occurs whenever I slow down to a fairly low speed and then accelerate. When I accelerate there is a hesitation for a second or 2. This is very annoying and could potentially be dangerous. I have contacted my dealer and he just says "that's the way they shift, no fix"??? Dealer also stated that the transmissions have a learning chip and shifts the way a person normally drives - that's total BS. I have had my truck for over 2 years and it still shifts poorly. Besides the above I love my truck very much, GM just has to fix this problem..." GM knows there is a problem. It has issued both notices to its dealer's technicians and also TSBs. However, it has yet to find a solution that works. There is a class action suit that you can learn more about here. Our questions for our members are; 1) Have you experienced any issues with your 8-speed, and 2) was the dealer able to fix it? Let us know in the comments below.

I have a 2004 Chevrolet Silverado 1500 4wd with the 4L60-e 4 speed transmission. Currently I have no speedometer and despite the transmission shifting very well, it skips second gear consistently (no intermittent functioning). This is the ONLY gear that it has issues with (reverse and the rest of the gears are good). Here is the story... I bought this truck being told the transmission was shot. Initially it would not shift past 1st and also had a functioning reverse. I had the tranny swapped with an equivalent from a suburban. It improved slightly but still there is no speedometer or second gear. NO ENGINE CODES have come up throughout this entire time including prior to tranny being swapped (this includes no ABS lights). Here are the different problems I have found on the internet that I have tried to rule out: VSS- A mechanic with a good computer states that all 3 Vehicle Speed Sensors read correct speeds in real time on the road Ignition switch- Already changed Fuses/relays- All appear to be intact and functioning Dash cluster- broken connections fixed restoring all function besides speedometer Transmission treatment- Lucas treatment put in in case this could be a sticky solenoid to no avail Grounds- All appear to be in excellent condition and no frayed wires visible Low Voltage- New battery in place Help me out! What I can see as being my next options are either changing out the ECU or the wiring harness, neither of which I am desiring to do. Any recommendations from your experience that I may have missed in my internet reading?

Story: transmission overheated @ 60k miles. Warranty replaced with new transmission. I’ve had the vehicle (2018 suburban LT 4x4) since new and always sit around 190 degrees give or take and back and fourth around 200 when towing. With the new transmission I keep hitting 210 up to 220 driving around town and not driving hard. I haven’t towed yet but tow often and I am very concerned and afraid to tow. I just finished a thermostat delete to test that out and driving for about 30 min around town and freeway it was over 190 and climbing. It took a while to get there compared to normal but still got hot. Dealership has no clue and the transmission shop has no clue. I need help in figuring out what could be causing the heat. I am so for an oil change and my AC blow nice and cold.

Ok so I have a 2015 gmc sierra 1500. after backing up and putting it into drive I get going for about 5 to 10 seconds ill get a jarring lock up for a split second. First time it happened I was going about 40 and I bounced off the steering wheel and left a little skid mark. It sounds like either my transfer case or transmission is locking up but it literally lasts for a split second then goes away. also I've noticed that after shifting from reverse I hear a loud transmission whine before it does it. This has happened at least 30 times for about a year and dealer says they can't recreate it. It's the 6spd tranny Also I know all about the normal GMC transmission clunk when shifting I have that too but I've learned to live with it. This is something else entirely. Its dangerous and I can't find anything on any forum mentioning this issue

How's it going , new to forum and hoping someone could shed some light. I have a 2019 silverado custom 5.3 w/ 6 speed trans with about 37k. A month ago the truck threw error p0741, it would Rev high and not want to shift so dealer replaced tcm and new fluid. A few weeks past and code comes back with trans temp running around 215* when it did so dealer replaced torque converter and said it was good to go. I took for a extended drive of so.e city and a Lil hwy for around d 1hr and Temps climbed to 225*. Is 225* high? Doesn't seem normal and dealer is saying they. Ant find anything wrong 20210429_195723.heic

I have a 2004 Chevy Astro van 2WD 4.3L with a 4L60E automatic transmission and something is seriously wrong, but I have yet to figure it out. I definitely need some help. I usually do all my own repairs and I am very mechanically inclined, but this has me stumped. I even consulted a friend who knows a lot more than me and he was puzzled and asked that I share with him what was wrong once it has been diagnosed. I would probably be willing to drop the big wad of cash down for parts for a remanufactured transmission if needed, or for a remanufactured rear end and new axles.... BUT the van is not worth spending $1,500 (or more) times TWO. I need to definitively be able diagnose the problem so that I can decide how much I'm going to have to invest to get it going again. I bought it used from a municipal police department that used it as a crime scene investigation vehicle and it has no hitch on it, so to the best of my knowledge it has never done any towing. Here is what happened and what I have checked thus far.... I pulled out of the driveway at work and after I had cleared the 2 lanes of oncoming traffic and was in the crossover in the median I let off of the accelerator and heard a slap, pop, or bang that sounded like it came from the right, rear corner. I instantly thought it might be trouble as it sounded like clapping/slapping two solid bricks together. I hoped it was just something I ran over. Then I pulled out and accelerated up to 55 mph. Then about a 1/2 mile down the road I heard what sounded like driving on a tire that was completely flat. I pulled off the road to check out my tires. I was surprised when they all looked fine. I realized something had to be wrong and I wanted to get my van to a better spot where I could investigate further. I put it in reverse to back up a few feet to better align me with the area I wanted to drive to, but the van would not move backwards. I wondered if something with my rear brakes had broken or locked up. I was able to move forward in D, but there was a good amount of resistance as the engine was struggling to move the van forward. There was a good clear spot nearby where I parked. I thought somehow something had broken in the rear brakes and bound things up preventing the van from moving as normal. I jacked up the van and removed both of the rear wheels, removed the pads & rotors, then propped the calipers out of the way. I put the transmission in neutral. I replaced the rear wheels as it was easier to rotate the tires by hand than trying to rotate the lugs on the hubs by hand. The tires spun freely by hand, but after about 10 revolutions there was a clang noise and the tires stopped. I rotated the tire in the reverse direction and it no longer made the driveshaft move as it had been in the forward direction. Then the clang noise again and the tire stopped rotating in the reverse position. Both front wheels easily rotated when spun by hand, so the binding wasn't coming from the front This made me think that it was possibly something going on in the rear end. I pulled the cover and I saw no obvious problems with the differential. I have the G80 rear end which I had never seen that type of rear end before. When I moved my tire forward by hand slowly there was no movement in the rear end, but when I put my foot on the tire and give it a spin the tire moved a lot and the rear end moves a little. I didn't see anything that looked worn or damaged in the rear end. I cleaned up the parts, cover, and magnet and put the cover on with a new gasket and replaced the fluid. While both the rear wheels were still off the ground I cranked the van. It was still in neutral, but both rear wheels were slowly rotating forward. Then I shifted into Drive and, with the engine idling, the wheels would pulse several rotations forward, then slow to almost a stop and then repeat the pulse & near stop. I couldn't understand why the surge and slow was taking place. Then, I drove it the 1/2 back to work to leave it in their parking lot. The van made all sorts of popping, grinding, and clanging noises. When I stopped I put the transmission in neutral, but it would not roll backwards. I tried reverse and the nose of the van dived down and the rear bucked up, but the van never traveled any distance in reverse. I pulled it forward a few feet into the nearest parking space. The van did throw a MIL code on the way back to work, which was a P0756 (PCM sensed an irregularity in shift solenoid B). I thought that I might need to remove the driveshaft and see if the transmission would turn the output shaft while in reverse. Also, I could try to see if there were and weird noises, pulsing, or resistance to the output shift turning when in Drive. But, I wouldn't necessarily know for sure the tranny was good if it only misbehaved while under a load. I had ordered a set of shop manuals about a week before all this happened, and they have now arrived but I wanted to see if anyone had any ideas about how to diagnose my problem before I resorted to the shop manuals. I get bogged down in them because there is soooo much information in them. How can I definitely determine if the problem is my tranny, my rear end, or both? Here is a video link on YouTube showing when I had the rear end cover removed: Here is a video link showing when the rear end cover and fluid were replaced and both rear wheels were off the ground in Neutral and in Drive with the van running:

Hello all. I own an 18 Silverado 1500 LT , double cab, 6’6” box, 6 spd transmission, I have opted to put 26” status alloy empire wheels with tire size of 305/26/30. Stock transmission gave out. Stock Transmission went out. They said torque converter and pump went out then everything else went with it. Was able to replace the entire unit with a remanufactured from GM. 1 month later, back to the shop (dealer). They covered the repairs because it was under warranty but if it goes out again they won’t because they believe it is the rims causing the trouble. However they will cover if it goes out with stock wheels. Which I will be putting back on. Has anyone else experienced issues with this type of truck and 26” wheels? I did research the “Unsprung weight” makes some sense, however only the transmission gave out, not my drive shaft, drive shaft knuckles, diff, just the goofy transmission which I know the 8 speed has had their share of ongoing things. How is it that a truck that is capable of towing 9k lbs has issues with no load on 26” rims. Pulling a payload in the bed of the truck and pulling a trailer should still have the same effect. If I can’t tow anything with the truck, then what is the point of a truck. I have went back to stock rims to see what would happen. Anyone with info ,thought , something sketched on a cocktail napkin would be greatly appreciated. I do thank you all for your time on this. I have attached the service ticket to this post.