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Hello all, I'm going to be adding the transmission oil cooler (GM Part Number 23409058) to my 2020 Trail Boss. I’m going to order the ACDelco Oil cooler lines (GM Part Number 86560008). Does anyone have any detailed photos of how the lines are run under the body, through the engine compartment, and out of the core support to their cooler? Any help is greatly appreciated. Thank you so much!

As everyone here already knows…”it shouldn’t take more than a few minutes” turned into me pondering how many fist sized dents I needed in my door panel for aerodynamic efficiency or the “golf ball” look. Anywho. I delved into the underside of my custom trail boss in an attempt to install a dipstick in my 6L80. Of course, I must mention that the 6L80 was present in the 4.3 models until at least the 2020 model year (RPO code MYC), this dipstick fits all 6L80/90 transmissions as far as I’m aware, in the 6/8 cylinder engines alike. Here is the order of operations. NOTE: TRANSMISSION CROSSMEMBER REMOVAL OR DROPPING THE REAR OF THE TRANSMISSION WAS NOT REQUIRED. FOR MY APPLICATION. Remove dipstick from tube to make installation easier. The dipstick gets in the way otherwise. Also, lube the seal and tube with white lithium grease to ease insertion. In order to access the hole where the plug is (that must be removed prior to installation), there is a heat shield that needs removal on the passenger side of the transmission. It is held on by two 10 mm bolts. Beware of the front one, it’s blocked by the bend in the shield, and too close to the catalytic converter to get a regular 3/8” ratchet and shallow well socket in there. After removing the heat shield, you can use a trim tool, your fingers, or a screwdriver to remove the plug where the dipstick enters the transmission (there is only one location it will go). Then, find the studs on the backside of the bellhousing, and locate the one below the starter hump. Using a 15 mm deep well, swivel, and breaker bar or 1/2” ratchet, remove the stud. Test fit and place it in its approximate location, but beware the ground strap on the back of the block, right next to the path of the tube, there is a chance it gets in the way like mine, and you’ll need to loosen it in order to route the tube unabated. 15mm bolt. Install your dipstick seal first, you can use a thin layer of white lithium grease for ease of insertion. Follow up by seating the tube in the grommet, and then reinstall your bell housing stud. Be mindful that torquing that stud could cause the dipstick to raise out of the hole, so it’s wise to keep light pressure downwards on the tube to ensure it stays in the transmission until you snug and tighten the stud. Once the tube is seated and the stud installed, make sure your O2 sensor wire holder/zip tie is still in its pocket on the transmission, and reinstall the heat shield. If you had to loosen or remove the ground strap on the block, reinstall/tighten the bolt. Use the procedure sent with the dipstick to check level and add fluid as needed. Mine needed 1 quart (this is typical, mine didn’t leak and hasn’t lost fluid.). This dipstick does work with aftermarket and deep pans. Lubelocker also makes a reusable gasket for the 6L80 and one for the 6L90 if anyone is interested.

I have a 2010 sierra 1500 4x4 with around 190k. Recently while driving from 3rd gear on up, the truck seems to almost stall,rev drop and power loss and all, and then regain power again. I have done a txspeed dod delete and thats about it upgrade wise. My question is, is that transmission problem requiring rebuild, or do I need to tear into the motor and look in there?

Hello, about 7 months ago I smoked my 6l80 transmission, removed it with the transfer case still attached last fall, before removing it I made the mistake of putting the transfer case (RPO code NQH) into neutral to aid with removing the rear driveshaft. Fast forward to about a month ago I finally had time to reinstall a new (rebuilt) transmission, upon reinstalling everything I noticed that my transfer case shift knob was not responsive and had no lights (other than on startup when it does a function check or whatever) I got a few wiring diagrams and checked over the whole system, replaced the transfer case actuator motor and the knob on the dash, still cannot get the POS to respond and do something. At a loss with this truck and contemplating scrapping it, it's had 4 motors, and 1 transmission in 126k miles, let alone over 30k in parts and labor. I recently got laid off and buying a fancy scan tool and/or having it sent to a shop is *NOT AN OPTION*. I desperately need advice and or assistance as to WTF I should do with this POS that has been nothing but problematic since day one. below I have sent all the PDF pages I have used to trace and track wiring schematics.

So I went ahead and purchased the "updated" thermostatic valve for my 6L80e, part number 86774933 referenced in the SB. installation look about 10 min and only required a 10mm and 13mm open end. I do my trans fluid and filter every 22,500 as per the service manual and my fluid temp would hover around 185-195 towing or not towing hot outside or cold. As i live in CT the ambient air temp can be 10 degrees or 90. After the installation of the new bypass valve the trans sits at 145 and never got over 150 on a 2 hour 116mile drive. I also think this is much better than the "pill flip" as you retain the bypass ability for colder weather so the trans still gets up to temp quickly. I have not yet towed anything to see if the temp would go back up to the 180-190 range but I figured I would share this info for anyone else who thinks a transmission designed to run at 192 degrees is crazy. Also for anyone who wants one and doesn't wanna pay if your truck is still under warranty the dealer will install one of these if you complain about anything with the transmission even if the "Customer complaint Cannot be replicated." that being said i got mine for $60 on GMpartsDirect.

Hey guys, I did the thermal bypass conversion to active by pass on my 2018 8L90. Did a step by step video because I hadn’t seen anybody do an actual full replacement video nor had I seen one on a 8 speed. Trans runs about 45 degrees cooler now. Check it out and let me know what you think. It’s the exact same procedure on 6 speeds just mounts different on the transmission.

2017 1500 SLT, 52kmiles, stock other than GM/Borla. Truck is never used for towing, but is my daily driver. I noticed recently there is an "odd" upshift between 2nd and 3rd at random times. Usually after driving for a while. Took it in to the dealer who says all is good, no burned fluid and can't duplicate the issue--they say they took it up to ~190. I drove the truck about 470 miles this weekend on vacation after dealer cleared it, but monitored the tranny temps more closely and noticed on the long highway drive with minimal cargo/passengers temp is sitting around 225-232. Ambient temps in the upper 90's. This seems high to me with very little load, but I never really paid attention to temps prior to the shifting issue... so no baseline to compare to. What temps are expected/normal?

2017 Silverado LT 5.3 4X4 6speed transmission 51,000 miles When I first bought the truck the transmission suffered from severe bucking or shudder under light load. GM calls it chuggle. The cause was "intermittent tcc delamination causing scoring on fluid pump". They replaced the torque converter, cover housing and pump cover along with a flush. This was at 10,000 miles. That seemed to solve the chugging problem. For the last year or so I have noticed that the torque converter unlocks and locks frequently at freeway speeds. When it locks, following an unlock, there is a noticeable lurching forward. This is not neck snapping but is definitely noticeable. This lurching motion also occurs when upshifting 4/5 or 5/6. While driving at freeway speeds (65 70mph) when I slightly let off the accelerator the rpm's rise about 200 then settle down. If I should slightly press down the same thing happens. However, when driving at a steady freeway speed, and holding steady on the throttle, on level ground I can feel this unlock/lock along with seeing the engine speed move up then settle down. If I engage cruise control on level ground it is worse and occurs more often. But, with cruise control on and there is a slight road incline there is no unlock or downshift. When I press hard on the throttle then it downshifts and accelerates fine. Locking/unlocking and lurching; I do not recall the transmission behaving like this in the early years. The dealer says if it doesn't throw a code then it is operating normally. I can see that there are times when it should unlock such as when under load, but should it be this happening this frequently and be so noticeable? Or maybe I am being too sensitive? Anybody experience the same thing? Is this normal transmission behavior?

Hi everyone, I’m new to this forum and I just want to get a good idea of how many miles everyone’s getting out of there 14-18 5.3’s / 6L80 combos and what type of maintenance y’all are doing to get there. I have 90,****** now on my 2016. I follow my service schedule to a T. Trans fluid and filter every 22,500 and engine oil every 4000. What’s everyone else do to get there trucks up to high mileage

It started the day before Christmas Eve - noticeable but minor rpm fluctuations (a few hundred rpms) while driving on the highway after being warmed up. About 5 minutes later, I felt the truck stuttering under light loading moving ~60mph - engine rpms below 1500. I checked the fluid and it was perhaps a tad low (very bottom of 'hot' zone) but was definitely not red/pink. I'm not sure if the previous owner had changed the fluid or not, but it didn't seem it. Over the next day, the shuddering got worse and entirely repeatable. Once the transmission fluid was warm, it would reliably shudder under light loading at slow highway speeds. Occasionally I could get it to do it on a hill at slower speeds too. It never happens under aggressive acceleration/heavy engine loading - this seems to work fine with no issues. I scheduled an appointment at the dealer for next Tuesday, the soonest they had available. In the mean time, I'm hoping to make sure I'm going down the right path and understand my best options. I found PIP5504 (attached) and related Torque Converter Diagnosis SI (attached) and tried to work through them as best as possible without the specialty GM tools. Diagnostics Occurs most obviously when transmission fluid is warm-hot Occurs in M5 mode as well as Drive Occurs both when in V8 and V4 (with and without AFM) Occurs with and without Tow/Haul Mode enabled Occurs with and without grade braking disabled Occurs under light load conditions Does not occur under heavy load conditions Using torque app, a couple misfires (less than 20 after an hour of driving, distributed across all cylinders) are noted, but the instances do not remotely line up with when problems are seen. Using torque app, spikes of TC slip is observed. Using torque app, RPMs go UP when TC slip is observed - these so probably not a misfire Working through the PIP, the symptoms seem to indicate either 1 (fishbite) or 2 (Torque Converter Shudder). I'm not entirely sure what fishbite is, but the service procedures are more or less similar. I don't have a GDS2 tool to command TC engagement, unfortunately, so hopefully the dealer is willing to do this properly. The original PIP5504 (not the C revision) had service procedures included that all seemed to point back to a fluid flush or replacing the torque converter. Knowing that my fluid was pretty black (didn't smell burnt though), I went ahead and got a new transmission filter and performed a fluid flush. 20 Quarts of Valvoline MaxLife fluid were flushed through (not here to debate fluid brands/types - it works with Dex VI and it's what was in stock at the store open on Christmas Eve). Observations Fluid was black Transmission pan magnet had fine metal debris (felt smooth between fingers) on it Photo included - what is a lot? Truck has 178,000 miles on it, this is probably the first time it was opened. One small piece of flexible (rubber?) debris in pan Flow through and out of cooler seemed OK from the start No signs of leaks Changes after Flush Shuddering is much reduced - but still faintly there. Doesn't feel like truck is going to come apart though. RPM fluctuations are still there - and perhaps more noticeable than before (probably because the shudder isn't overshadowing them). Using torque app, Torque Converter Slip is still present when RPMs fluctuate. It appears there is no change to the frequency or amplitude of slip. Questions For those familiar, does the amount of metal on the magnet look typical, or does this look like a sign of an internal failure? Any other ideas for what the issue could be? Any other diagnostic tests that would be helpful to zero in on the root cause? The PIP points to replacing the torque converter as the next step. Is there any way that with all this identified, the transmission itself could be the culprit? Living in MA in the winter without a garage, I'm almost certainly going to have to have the shop perform any replacements and don't want to pay for labor twice. If so, thoughts on a reman unit vs. having a shop repair it? I'm well outside of any warranty and see a lot of people going back and forth with the dealers while they throw parts at a problem. Any tips for reducing bad service and getting it right the first time with them? Am I doing more damage if I keep driving on it for the next week? I'm open to thoughts/suggestions at identifying the cause and next steps. Vehicle Information 2016 Silverado 1500 LT Z71 4x4 6-speed auto (6L80, MYC) 5.3L V8 178,000 miles NOT tuned in any way Daily Driver - mostly highway miles Used for occasional light towing (~12,000 miles spent towing an 850 pound teardrop trailer) Generally driven gently (boring, I know) Thanks, -Sean MC-10118277-9999.pdf PIP5504C.pdf Torque Converter Diagnosis SI.pdf

Truck was shuttering a little, almost felt like it was slipping saturday driving in the city, highway fine. Sunday morning there's a whine from the front of the trans at idle. 5 mins down the road the trans/engine revs are jumping all over the place catching and slipping or shuddering till eventually something let go and it starts to coast with the engine reved up. No movement in any gear, engine revving fine, just no power being transmitted in fwd rev or low. Gets towed to the dealer sunday and monday they say its moving fine at least in the lot, they haven't looked into it further yet. Any ideas on what would cause this? It wouldn't even try to move and the next day its moving fine. Also any TSBs with the torque converter or 6 speed trans that might be related? If it is the torque converter do they rebuild the trans as well or just try to flush the debris out? Fortunately its still under warranty (just) but, I like to be informed. Also don't want the trans to go 20k down the road when its out of warranty because it was contaminated. Truck has 145K KMs on it.

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.

Hi all, I'm new here and hoping y'all will be able to help give me some direction. I have a '15 Yukon XL Denali with the 6 speed MYC transmission and almost 140k miles, my transmission has begun shuddering when I'm driving between 25-35 miles an hour, does not seem to do this at really any other speeds. I spoke with a dealer who said their suggestion is just to go ahead and replace the transmission, this feels a little extreme at this point since Im not having hard shifts etc. I've owned the vehicle for the last year and put about 27k miles on it in a year. I have no records of any previous transmission maintenance and the fluid looked good when we purchased it. I know that dropping the pan is a pain in the neck, but I'm thinking that I need to change the filter since I have no idea how old it is. Husband is out of town and I'm wanting to get this dealt with ASAP. I'm pretty capable of doing a flush or dropping the pan if I have a good write up to follow, so any advice would be much appreciated. Also, what fluid have y'all had good luck with? Thanks, Jenn