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Folks with the 159’ trans thermostat, over long drives does your trans temp still climb well over the 160 mark? I drove my 17 Sierra 220 miles today and by the end of the drive it had reached 180’ in 80 degree ambient temps. I would like to think the cooling system is efficient enough to keep it lower..?.. The condenser/trans cooler was replaced a while back, but this issue happened before that. Once I parked and let it idle, it dropped to 165 in 15 minutes. I’m not concerned right now, but I will be when it gets too 100’f out (Alabama weather, yay) and I’m pulling my boat to the beach or my other truck to and from the track on the flatbed. Do y’all think I’m missing something here and I have some issue? Or is this the standard and I need to just add an external cooler? When I first swapped the 159 thermostat( when the new trans was put in) the temps stayed at 145 all the time, but it hasn’t been that way in quite a while. I even pill flipped it and all that did was make it take forever to warm up but to the same effect. Full system fluid change was done about 1k miles ago with oem filter and ac delco dex6 fluid. Trans has around 47k on it. Truck has about 127k on it. Do y’all think I’m missing something here and I have some issue? Partially plugged line? Or is this the standard and I need to just add an external cooler? Any help would be appreciated at this point..

I have a 2020 RST with the 3.0 LM2 Duramax with 79k miles… the flywheel failed when I was driving down the highway and left me dead in the water.. I had it towed to the dealership 4 weeks ago and they called today and said the transmission and the engine needs to be replaced. Has anyone experienced this with their trucks? I never towed anything heavy and was religious with service.. luckily all covered under the 100k powertrain warranty…

OK everyone I want to give thanks ahead for any advice and help. Truck in question= 2003 Chevy Suburban Z71, 5.3 L Transmission= 4L60-E So the story started when I was going down the road at about 50mph in cruise control, when suddenly I heard the engine begin to rev up. I hit the brake to take it out of cruise control and the engine stopped revving up. Apparently I lost transmission of power from the engine to the wheels because no matter what gear I put it into now, I get no movement from the vehicle. No reverse and no D1, 2 or 3. When I put the vehicle in park and attempt to push the vehicle it will not roll. When placed in any other gear I can then roll the vehicle freely. Before this happened: Since owning the vehicle 4x4 has always been shifty.....hehehe...sorry couldnt help it. I have the model where there are 4 buttons with lights the buttons are located left hand of dash near the turn signal. When I first got the truck sometimes it seemed like it didnt want to switch between gears. for example I would have to hit the button multiple times before it would switch and even then it seemed like it hadnt really switched but the lights would indicate it had. Most of the time the light for the button I selected would flash multiple times and then return to previous selection. Often times after turning the vehicle off and then returning to vehicle to go somewhere I would find that the light has switched back to a gear that it wasnt in when i left the vehicle. It seems to favor 4x4hi. As of lately I havent been able to get the lights to switch at all. It seems to be stuck in 4hi permanently. I have tested the 4wd switch and its fine. I tried unhooking battery for half hour with lights on to reset PC. I then reconnected battery cable and turned vehicle on but not start it. Then I pulled a bunch of fuses and plugged them back in. ( seen it in a video and the guy said it was supposed to wake up the TCCM) Well that did nothing. I have the truck off of all wheels right now and was trying to figure out if the transfer case is stuck in neutral. With the truck in drive as I turn the rear draft the front moves also. I am assuming that means it is in 4wd. But should I have someone hold the front drive shaft while i turn the rear drive shaft to confirm its not just from friction or something. I actually have the front drive shaft partly out right now in an attempt to get at and remove the shift motor and manually put the transfer case into 2hi. I am also considering changing out solenoids. I have gathered it is unlikely the shift solenoids. Is it possible it could be one of these: 1 * EPC (Pressure Control) Solenoid 1 * PWM Solenoid 1 * Manifold Pressure Switch 1 * TCC Solenoid w/Harness Another thing I suspect which would be an easy fix is the transfer case fluid level. I removed the fill plug and nothing came out. I can tell it has been leaking. I would have already topped it off but I have been stuck at home (no running vehicle lol). Could low fluid cause this issue? I hope that's all it is lol. Anyways I got a ride to the store tomorrow and to look at a back-up vehicle. Anything you guys recommend to grab from the parts store while I'm in town tomorrow? What would be your guys recommendation on how to solve this problem and fix it? All help is appreciated. thanks in advance, Aaron

Were working on getting an 86 k10 back on the road. The trans slips between gears and doesn't have a working OD. Does this sound like a master rebuild kit fix, or should we be looking for another trans and just swap it in. I'm sure we could work through rebuilding it, but this would be my first time trying to fix one. Anyway, just wondering what to expect. Things like, how do you know if the pump is good, torque converter, any hard parts that could be broke that would save me the cost of the rebuild kit in case I just have to replace the trans anyway...etc... Thanks!

I am currently helping my father with his transmission rebuild for the 4l60e on a 2002 avalanche, he installed a transgo 4l60e sk shift improvement kit along with adding a corvette servo. he installed a cam on the 5.3 and the engine runs flawlessly and for the transmission he added a 3000 stall converter. the transmission will shift into reverse fine and will shift into second with using the manual shift, however the transmission will not shift into drive. the valve body has been checked over and over again and everything seems to be in place. Has anyone else had this issue or know what may cause this? Any help would be greatly appreciated!

I noticed my transmission temperature getting quite high when driving on trails or towing through traffic so I decided to add a secondary Derale 13900 transmission cooler in addition to the stock front mounted cooler. My truck is a 2020 Custom TB with the 5.3 and 6 speed 6l80e. This kit came with everything I needed except for a couple fittings, and the fan is wired to an ignition power source so it won't drain the battery. You can see that it is mounted to a winch mount that I had made, but without the winch there that would be a great spot to fit the cooler. Essentially I followed the return cooler line from the transmission forward until the hard lines split off into two rubber lines with the return going to the driver side of the truck. NOTE: The hard lines are 3/8" but the rubber line is 1/2" (learned that the hard way). I first held the cooler in place and measured what angle it needed to sit at and tacked together some mounts, then after a couple of iterations got it to where it fit and the skid plate did not interfere. I then finish welded, drilled, tapped, and painted the mounts. On the cooler itself, I mounted the 180 deg thermostat to the lower connection. With the cooler location determined, I then measured and cut the 3/8" rubber hose in the kit. I then clamped the return rubber line on the truck, cut the rubber hose, and connected the 3/8" cooler hoses to the pre-existing 1/2" hose on the truck. I used one 3/8-1/2 straight barbed connector and one 3/8-1/2 90 deg barbed connector. Some zip ties to tidy up the lines too. Wiring was simple as well, easiest way to get a for sure ignition power source was to get a fuse tap from autozone for a micro2 fuse and then you have a fused ignition source. Ran the power to the thermostat and then positive from motor to the other side of thermostat and the ground to the frame. The hole in the skid plate has an aluminum mesh behind it to keep small rocks out, and it's pretty high up so shouldn't see much abuse. Haven't given it a full test for cooling capability yet but the fan is nice and strong so I have no doubt it'll help. For about $200 total I'd say its a great upgrade for anyone who tows in the city or hits the trails on any steeper terrain.

I have a 1988 GMC G3500 Vandura Box truck with 350 5.7L TBI. I am renovating it to be an RV. bought new motor and had a mechanic I know and trust do that and a bunch of other stuff. It drives great. Runs great and shifts great; EXCEPT when I need to down shift to pass another vehicle or going up a mountain here in West Virginia (and there are allot of them, lol). My son is a mechanic but in Alabama. I texted back and forth and he mentioned the things I put as tags. TPS, modulator and adjusting the TV cable. I have the service manual and two other manuals. Anyone else have the same or similar problems? I downshift by using the shifter on the column. any help is greatly appreciated. email is: [email protected].

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?

My 4l60e is starting to show its age a bit. Not ready to condemn it yet but it occurred to me that it would not be too difficult (on the scale of trans swaps) to put a NV4500 from a GMT-800 HD truck in place of my 4l60e. I've done a bunch of research on which part numbers I would need and it seems mostly manageable but I have run across something I can't find the answer to online. My NP246 transfer case has the 27 spline input shaft because it's currently hooked up to a 4l60e. The NV4500 has a 32 spline output and was never (as far as I can tell) offered with a NP246, just the NP261 it seems like. However there's a part number for a 32 spline input shaft for a NP246. If I install that input shaft, will I be able to put my NP246 behind a NV4500?

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?

I have a 2015 Chevy Silverado 1500. Yesterday driving down the interstate with cruise control on I noticed the truck shifting back and forth between fourth and fifth gear. It seemed to hold fine when I would take the cruise off and hold the speed myself. It would also stop when pulling a hill as it would stay in fourth gear. Today it seemed to be doing the same thing in the lower gears and the check engine light came on as well. Planning on hooking it up to the scanner tomorrow but am looking for any ideas of where to start.

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

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.

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

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!

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

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

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.

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

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

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: