2015 Silverado experts - transmission shifting/noise

I have a 2015 Chevrolet Silverado 1/2 ton 4 door with the 5.3 gas engine. 150,000 miles. I am noticing some unusual transmission noises and shifting. The first thing I notice is some of the shifts are more abrupt than they ever have been - probably those under 45 mph. Most of the time the shifts have been smooth and not even noticeable. Now some of the shifts up and down have a slight clunk noise or a noise like a slap. Secondly going down the road at 55 I wonder if the transmission is shifting or the torque convertor is unlocking. Sort of feels and sounds like you hit a crack in the road with both front tires, but this road is newly asphalted and smooth. Thirdly, when I back out of the driveway, stop, turn the wheels to the left slightly, and put it in drive 20 - 30% of the time it will sort of stop/go/stop/go for a few feet. The transmission is running about 194 degrees pulling the camper. Transmission has never been abused. It has pulled the camper (5000 pounds) about 5000 miles the last two years. U-joints are OK. Transmission fluid is fairly clear, not perfect, but fairly clean. Am I starting to get some sticky valves? Would a fluid flush be beneficial? Would a plugged filter cause my problems? Fluid and filter have never been changed. Still pulls the camper without slip. Thanks.

Fluid and filter have never been changed.

At 7 almost 8 years old and 150,000 miles a transmission fluid change would not hurt anything.

Line pressure, shift ''feel'' and timing are 'puter controlled, first thing I would do is have someone with a high-end scan tool take a look at transmission codes and pending codes and adaptive shift strategy.

It isn't stuck in ''tow-haul'', is it?

You say ''when I back out of the driveway, stop, turn the wheels to the left slightly, and put it in drive 20 - 30% of the time it will sort of stop/go/stop/go for a few feet''.

Makes me wonder if the front axle disconnect is releasing? You aren't running it in automatic AWD, are you?

4 wheel drive if OFF. Yes, it does sort of feel like when the 4 wheel drive is turned on and turning. But, the 4 wheel drive is turned to OFF. Will check that it is actually off. Thanks.

Does it get a growling sensation at lower speeds, and the tach drop down and back up a few hundred rpm? If that is what is happening, the torque converter is failing, and the metal from that damages the rest of the transmission. The fuel economy strategy of the 14 and up trucks is very hard on the torque converter clutch on the 6L80E. The heavy use of that already small clutch distorts the torque converter cover, which leads to hot spots on the clutch, which leads to delamination of the clutch plate, which then begins steel on steel contact. If it ends up being rebuilt, make sure the rebuild uses a billet steel converter cover. The originals are stamped steel, billet provides the support to keep the converter alive. There is also a fluid thermostat upgrade to drop the fluid temp a tick. 150K is a lot of miles to get out of a 14 up 6L80E, I'm usually replacing them at 100-130. You've done well with it.

Here at my Ford Dealership we have found that fluid starts to break down consistency and the solenoids will not shift right, if a vehicle tows a trailer then it should be done more often, you are way over due for a fluid change
hopeful there is no internal damage.

Would a fluid flush be beneficial?

Sure, it will either fix it or finish off the transmission. Pretty much anyone I have encountered who has waited to 150,000 to do a transmission flush for the first time, ends up replacing the transmission.

Either way the problem is solved.

If you have the 6 speed, Trade it off.

Some on YT give me heck for having my fluid changed every 60K.

Someone on YT gave me heck for owning Kubotas and installing steel roofs. Give them time.

I agree, at 150k it is normal for them to just plain wear out in my experience.

As far as I am concerned, flushing is a scam invented by BG to sell more of their snake oil.

First thing - there are too many different transmission oils. Ford uses either dexron 3 or mercon 5. There are
tqo. GM uses dexron 6. That makes 3. CVT transmissions use their own oils. There are at least 3 different CVT
oils. That makes 6. Now, add in Chrysler's ATF+4, and you have 7. Toyota, nissan, subaru, et al use their own
proprietary oils. Now, wee are over 10.

How many of those oils are still in the machine used for flushing? Remnants of each one?

What oil is used for flushing? And how completely is a transmission (or the machine) flushed out? After having
been rebuilding transmissions most of my life, I can tell you that there is NO WAY to remove ALL of the oil in a
transmission without disassembly. Flushing also neglects the filter.

To me, flushing is just some more snake oil.

Oh, i change mine at 25,000, and the first one is the most important,but i get 350,000 miles out of a tranny too!

At this point I would avoid a flush. Take it to somebody that will actually drop the pan, change the oil and filter, and give it a cleaning and good once over. If there is debris in the pan (which there almost certainly is), flushing them has a tendency to stir things up ruin the transmission.

Transmission should be serviced every 45k if I read my manual correctly.

Vito

(quoted from post at 08:45:50 07/26/22) Transmission should be serviced every 45k if I read my manual correctly.

Vito

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or not at all, and run until failure.

You should be on your 3rd or 4th transmission drain and fill. If the fluid in the pan has 150K on it you are probably living on borrowed time. I believe the manual says every 30 to 60 thousands miles. Every 30K if you are towing with it. The other one you are probably missing is changing the transfer case fluid - its pretty important on those Auto AWD transfer cases.

I bought my Tahoe and it had never been changed at 100K. The transmission fluid and the transfer case fluid were both black. The Transmission fluid should be red - the transfer case fluid on my model was supposed to be blue. I put another 70K on them without an issue - and change the transmission fluid twice because the drain and fill only gets about half.

Actually Mercon, Dexron 3 and Dexron 6, Mercon LV and most of the imports are all the same oil. You can use Valvoline Maxlife Synthetic - about $25 a gallon at Wal-Mart.

Ford's Mercon V is a little bit thicker oil and more similar to the old Type F than the old Mercon. Supposedly anything using Mercon can use Mercon V but.....

The CVT transmissions have their oils as they are doing totally different things with their lubrication.

I know you are on a roll I understand... I don't think you can flush one of these. Maybe you can with the right Equitment I don't seen enoufh of'em to invest in it.. It takes more than a flush machine.

I drop the pan clean then fill start it up and run fluid out a cooler line till I see clean fluid (there is more to it but to keep it simple) That's it that's all you can do.. This will eat $400 up and not a big kill at that because its a time eater : (

OK so you don't do anything when it fails take the hit pay up... BTW I have a customer with one that has 525K on it at 225K I told him he was riding on barrowed time it was no worth the cost to service it again.

As it is now its starting to have issues he saved $2000 not servicing it I do think the service before 225K extended its life.

They all do now . The over running clutches have been eliminated . Now the shift is clutch to clutch at the best guess of the computer . If you tweak the throttle or brake when Bessy thinks she should be shifting , the result will be a clunk and jolt .