The recently accumulating anecdotes suggest that the tcc is not unlocking, during deceleration to a stop. For my truck, this is an intermittent problem, but for @nluchau's truck, for example, the problem is chronic. @nluchau, when did you first notice this and did it begin as an intermittent malfunction and progress to a chronic one? I'm starting to think this is a defect in the design of the tcc and this problem might eventually affect all 6L80 trucks as they age and get past 50k miles.
My truck's tcc lockup by itself is not harsh or jerky. For my 2016 Silverado 4.3L V6, harsh or jerky describes the 3-2 and 2-1 downshifts as I come to a very gradual stop and the tcc has not yet unlocked. At zero throttle, decelerating to a gradual stop, my truck's tcc seems programmed to unlock after the 2-1 downshift, just in time to NOT lug the engine before shedding those final 2 or 3 mph. In other words, under the described conditions, tcc unlocks at the "last minute" so that engine RPM stays above or at 600 (idle) as the truck slows to 3, 2, 1, and finally 0 mph. I'm considering buying an hp tuner at hptuners.com just so I can play with the tcc minimum speed (minimum unlock speed while decelerating). It seems if I could raise tcc min speed to maybe 10 mph. then the 3-2 and 2-1 downshifts would occur while the tcc is unlocked, and so the torque converter's fluid coupling would absorb the 3-2 and 2-1 downshift harshness and all would be good.
@nluchau, are you feeling the tcc (torque converter clutch) lockup? At light throttle, it can occur (is permitted by a data table in the TCM) any time after 2nd gear is engaged, so your 2-3 shift could happen simultaneous with the tcc lockup. At 1/8 throttle, with my truck, tcc lockup occurs after the 1-2 shift. At 1/4 throttle, with my truck, tcc lockup occurs after the 2-3 shift. This suggests the TCM has some leeway on its deciding when is a good time to lock. With my truck, the tcc lockup is much slower than the gear-to-gear shifts. The slow lockup deserves the "ease into gear" characterization, so I was wondering if you have the tcc lockup event properly categorized given that you didn't mention it. With a cold transmission, below 32F, the TCM does not lock the tcc at any speed, until the transmission temperature gets above 32F. This can give people in colder climates additional diagnostic info... Your thoughts?
I'd have the dealer correct the fluid level free of charge since they're obligated to follow GM instructions when doing repairs. I can't imagine a TSB instructing the tech to overfill the transmission. If they claim the dipstick is wrong then have them get you the correct dipstick. SMH on your dealership.
Ain't THAT the truth!
It's conceivable that the TCM has a coding error that adapts to "idle" throttle position changes caused by having the a/c on (higher throttle position needed to idle at 600 rpm) or by having a less restrictive exhaust (lower throttle position needed to idle at 600 rpm). Perhaps there exists a coding error that mishandles the default idle throttle position and properly handles the other 2 throttle positions I described above. I noticed on my truck that if I brake to a stop (using my left foot) while having the throttle only a tiny bit open, the 3-2 and 2-1 downshifts are much stiffer. So this could be a 3rd idle position. Has any reader of this thread actually gotten revised/updated shift tables uploaded into their TCM by the dealer under warranty? I challenge GM engineering to release a technical document describing the design objectives and features of this advanced transmission that learns how I drive. Does it compensate for how I drive? Does it shift earlier or later because it has learned I am a lead foot or slow poke? How long does the learned behavior persist? Or once it learns I am a lead foot, does it relearn only with a battery cable disconnect? Or do we all have to get hptuners in order to fix these issues?
There's no substitute for round tires. Ever time you buy a set of tires you gamble because the retail tire industry always blames 60-90 mph issues as balance issues, rust jacking issues, or "they all do that." Tire manufacturing is like sausage making. Bad optics and questionable results. The tread belt has to overlap itself somewhere. Better hope those new tires get their tread belts properly placed on the ol' tire production line.
Note that: 1. Most car manufacturers buy their auto-dimming mirrors from GENTEX. Most of the mirrors available on ebay (new or used) are GENTEX mirrors. 2. WT trucks (trucks with Work Truck trim level) do not have a compass as equipped from the factory. 3. WT trucks do not have an auto-dimming inside rear-view mirror as equipped from the factory. Instead they have an old-style manual-dimming prism-based mirror which unfortunately is a few inches out of the reach of most drivers including myself. It requires an extreme stretch--while driving--to flip the tab on the bottom of the mirror to change from un-dimmed to dimmed and vice versa. Not very safe! I replaced my factory mirror with a GENTEX GNTX-455 mirror with built in digital compass. It fits the existing factory glued-on mirror mount and works as expected. The compass dims automatically at night. https://www.ebay.com/itm/Gentex-Auto-Dimming-Universal-Rear-View-Mirror-with-Compass-GNTX-455/173319918081 Adding an auto dimming GENTEX mirror WITH COMPASS solves 4 problems with GM trucks with WT option levels: 1. It eliminates the image echo at night when the dash lights are reflected multiple times by the rear window and mirror in the manual mirror image. With the LCD based GENTEX mirrors, there is no prism and therefore the reflection of the dash lights only occurs once. (WT owners will know what I am talking about.) It makes it much easier to look-past the dash lights reflection when backing-up at night. 2. You can add a compass since otherwise in a WT, you have no compass. 3. There are no On-Star buttons on this mirror model (GENTEX GNTX-455) and that fits the WT perfectly since it doesn't have On-Star vehicle tracking. 4. The out-of-reach problem is solved because the mirror dims automatically. (The initial mirror position adjustment will still require a stretch but this can be done while parked.) You can add a compass-equipped GENTEX mirror to any GM truck since the compass is entirely contained inside the mirror and does not require any additional wiring beyond what is required to use a GENTEX mirror that does NOT have a compass. All you need is a switched 12V feed (IGN or ACC) and a ground. The outside temperature display is not needed--or wanted--since it's already available in the RPO IO3 radio display and a temperature signal may not be available in the overhead console. It takes 15 - 30 seconds for the GENTEX mirror to transition from daylight mode to dimmed mode, or from dimmed mode to daylight mode at 70 degrees Fahrenheit. Upscale GM trucks provide a backing-up signal to un-dim an otherwise dimmed GENTEX mirror if backing-up at night where lights and glare are present. But since the mirror is so slow to change modes, most people are already done backing-up before the undimmed mirror can assist them. I did not bother to provide a backing-up electrical signal to the mirror to enable this ridiculous feature. The GENTEX 455 has only one button and it is to toggle the dimming feature on/off. That is a more logical way to un-dim the mirror for those few times you will ever want to un-dim the mirror for backing-up. Even then, you will have to wait 15 - 30 seconds before the mirror regains full reflectivity.
I have a 2016 4.3L and 6L80 and it too behaves like a 16 yo kid downshifting a manual transmission (using the clutch properly) 3 to 2 and 2 to 1 as his truck comes to a otherwise casual stop. The gear clutch engagements are about what you'd expect with the 16 yo driving a manual trans and doing the downshifts himself with zero throttle and an engine at idle rpm. There is no roughness beyond what a 16 yo would consider "sport downshifting" and therefore I am not concerned about any damage from this behavior of my 6L80. But I *would* like to fix this. When I am coasting to a stop, and my 6L80 downshifts 3-2 and a few seconds later 2-1, I can feel the mechanical coupling of the TCC (torque converter clutch) is energized (the torque converter is locked) during both the 3-2 and 2-1 downshifts and only unlocks when vehicle speed drops to 4 or 5 mph, saving the engine from being dragged below about 600 rpm. If the TCC would unlock sooner, those harsh 3-2 and 2-1 downshifts would be softened by a TCC unlock and transition from a mechanical coupling to an hydraulic coupling. Is this bad TCC behavior by design? It might be. I discovered an excellent youtube video on tuning the 6L80 using hptuners at https://www.youtube.com/watch?v=1L006vkWbkQ At time 1:12 in the youtube video, a trans table for a 4L60/65/70 is shown. I captured the frame and reproduced it below. Studying it reveals some useful insights about hptune and GM's electronic transmissions shifting strategy: 1. The minimum gear where TCC can be engaged is set in a table. In the 4L60 example below "Min Gear" is set to 3rd gear. Look for it in the frame below. It is in the Torque Converter table. 2. TCC lockup during acceleration is set in a table. In the 4L60 example below, in the 3rd sub-table under Shift / Lockup Data (MPH), TCC lockup is permitted in 3rd gear at or above 32 mph with zero throttle and only at or above 127 mph (!) with 88% to 100% throttle. 3. TCC unlock during deceleration set in a table. In the 4L60 example below in the 4th sub-table under Shift / Lockup Data (MPH), TCC is forced to unlock below 29 mph with 0 throttle, etc. Presumably these are factory settings. Look for these values in the frame grab below and you will start to understand what hptune might be able to do to help. Presumably the corresponding table for a 6L80 would follow a similar protocol. Somewhere along the way I learned that the 6L80 is more aggressive saving every last drop of fuel, so TCC Min Gear is set at 2, while the 12 MPG 6.0L 6L90 is given a pass with its TCC Min Gear set at 3. GM has decided 6L90 users aren't as fuel economy conscious, apparently. (I used to have a 2500HD with 6L90 and TCC lockup waiting until after the 2-3 up-shift made a big improvement in drive-ability.) Conclusion and Plan: the objectionable 3-2 and 2-1 downshifts could probably be fixed by raising the minimum speed values for TCC unlock by a few mph in the last 2 sub-tables under Shift / Lockup Data (MPH). The tables for the 6L80 would look slightly different, but the general idea is the same. For the 4L60 above; it would be analogous to changing line 3 cell 1 from 32 to 35 mph 0% throttle accelerating (with similar mph adjustments across the table for non-zero throttle positions) and changing 29 to 32 for the last sub-table 0% throttle while coasting (with similar mph adjustments for non-zero throttle positions). Remember, the 6L80's TCC Min Gear is 2, not 3, so lock and unlock speeds will be substantially slower. But I'd also change Min Gear to 3, to get that 6L90 drive-ability improvement. Your thoughts? Questions?
My $290 install was 3 steps: 1. I installed the camera and plugged it in to the junction block/vehicle wiring. 2. I let a day go by just in case the radio needed to already know of the camera before accepting any camera add reflash. I do not know if this mattered. 3. I took my truck to the dealer (I made an appointment) and they said they'd do it while I waited. It was done in about 30 minutes. Is there any chance the reflash failed because the camera was not plugged in and therefore was not yet recognized and did not respond to the reflash software? I could imagine reflash software "hanging" if it could not see or communicate with the camera. Hung reflash software is often what causes a brick. The technician should be asked about this and any knowledge gained should be posted here if only to help the next guy. Customer satisfaction teams have the power to make things right. Refer them to GM's Upfitter's Guide. Concede that you have no basis for a legal claim. But then appeal to their sense of justice and ask for the outcome described in the Upfitter's Guide, without the unexpected expense of replacing your radio. I hope they see this as "the right thing to do."
My dealer also did not warn of the possibility of bricking the radio. And it was clear they hadn't done it before, because the technician gladly accepted my printout of the upfitter's guide. Did you have a chance to mention (or provide them with) the upfitter's guide (referenced in my earlier post)? Their assigning the risk to you implies that any upfitter following their instructions faces the same risk. Something doesn't sound right.
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The wiring using the tailgate harness described in my previously posted comments is complete all the way to the tailgate handle and supports the camera (and the lock/unlock solenoid if your handle has the solenoid). A waterproof 2 pin connector is also provided at the end of the harness so it's plug and play for connecting to the lock solenoid. But if your factory truck is like my 2016 Silverado, the harness that came from the factory does not have locking tailgate as an RPO option, the "lock" wires are not present in the tailgate harness. You will have to buy the tailgate harness like I did, as explained in my previous posts and in the upfitters guide.
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