GsBowtie

That's in that transmission most likely and is the dreaded 3-2 downshift clunk. Mine does the same thing at times and mine is a 15. Sometimes it's great, sometimes it clunks

My truckjust turned over 10k miles last week. I haveabout 10150 on it now and the transmission tuning is still pure crap. On back roads it lugs the engine in 5th gear, 1k rpm doing 35 mph and i get a driveline vibration. Then i sometimes get hard/clunky downshifts 4-3 and 3-2. Does this whether I'm in M mode or not. Had it to my dealer yesterday and the tech didn't even drive it. Said based on my description this is how these transmissions are. He agreed with me that they are crap and it would upset him too, but there is nothing they can do to address this, which to me is piss poor. After spending this much money on a brand new truck, we should not have to be told there is no fix for this, just live with it? Can't get a tune without jepordizing my powertrain warranty either. So it's very very frustrating.

Short answer, no. You're local tech should have been able to check vaccum. However, these new trucks are very complex so it takes some understanding of how everything is integrated. It's not getting any easier by any means

Well, for awhile there mine was pretty good, but recently has gone back to clunking on certain downshifts, making some sort of rubbing noise when the transmission is lugging the engine in 5th gear on back roads with a 35mph speed limit, it's slight but it's there. Mine is the 6 speed. It's ridiculous to have such a piss poor transmission in a brand new truck with 9800 miles on it. This is by far the worst shifting auto. Trans in a new vehicle that i have ever owned. How GM could release a vehicle with a transmission that shifts, clunks, luggs the engine, and just performs poorly overall (although the trailer tow mode is very good) etc is beyond me. Part of its on me though. I noticed on the test drive of two new 15s when i got mine that the trans didn't seem to shift right. Of course the 14 left over F150 i drove shifted great and with the 3.73 gears seemed to have great acceleration (5.0 V8) I do like my truck, but absolutely hate the transmission and laggy throttle tuning

I'm not in the running for this. 2015 z71 cc, bought in may of 15. 9800 mi or so. No major issues to date.

My brother's 14 had this around 40k and needed a new radiator. If under warranty take it to the dealer. It should not do that

I had the tsb done on my 15 a month or two ago and it's been rock solid since. No movement at all. This is the tsb with the shim kit and the extra clamps (black) next to the white factory ones. Seems to working so far. I didn't have a bunch of left-right movement before, but it was there and i didnt want it to get worse. So far so good.

Flapper valve in the exhaust possibly? I don't notice any noise like that in my 15, but maybe I'm just not noticing it

These direct injection engines have noise at idle. It's probably normal

I thought i posted this prior, but, i checked my 15' Silverado, 10/14 build date this morning. It appears that my truck already has that bracket installed on it from the factory. I can see the muffler from the top side and the sensor and it connects the two lines.

I just looked at my truck. 10/14 build, 2015 MY. My truck has the muffler, but also appears to have the bracket already installed. It's mounted sideways between the two ac lines and is near that muffler. Hopefully mine is good to go

Update; no real change (with vibration, i had none before ) i can tell on my truck with u bolts torqued to 79 ftlb and my clamps on the aft portion of the spring, 3" from the end (top 2 springs only) I do believe one change i do notice, unless it's just my mind wanting me to, is the forward to reverse clunk is gone and the movement i felt sometimes on the transition from my shop floor to driveway seems better. This could also just be in my head, but the rear suspension seems more solid now as well. All in all a good change for me, so thanks guys!

I have no vibration issues, but sometimes feel a clunk when shifting from forward to reverse and sometimes when I put my truck in gear before the rpm drops to normal idle. So I decided to check my u bolt torque. Mine were in the neighborhood of 50 ftlb. Not enough in my opinion, especially considering I tow a 6000 lb travel trailer. I also didn't like how the rear portion of the leaf spring did not have any clamp holding the two leafs together from the axle all the way to the rear, so I put a clamp on the rear about 3" from the end of the second leaf. So now at least the front portion of the leaf has the factory clamp, and I have the advance auto one on the rear. I painted the clamp black before I installed it to prevent rust. I'm interested to see if this will get rid of my clunking. If it has an adverse effect I'll let you know

That is a huge rig! Very very nice looking truck and trailer. Glad you made it ok.

Even empty your asking an awful lot of a half ton truck with that rig. Personally i would not do a trip that far with your truck. Think tail wagging the dog. What will happen if you have to stop quickly? Granted the brakes on my truck is excellent. Your in 3/4 ton truck territory. Just my .02. A 35 foot tt is a huge rig. My trailer is 24 foot and I wouldn't want to go much bigger with my truck