Usually happens between 1400 and 2200 rpm when at idle speed. I have a 2015 silverado LT z71 with BDS 6in lift and 35s on it with stock size wheels. I just took my truck in yesterday. Advisor told me today that the lift and oversized tires is what they "think" is what messed up tranny gears 2,3,4,5 an 6. They downloaded the ecu data today and sent to GM for review to make sure i didn't program or tune it. Nothing tuned or programed. This blows, it has 58k i purchased that extended warranty to avoid this crap. Maybe i shouldn't have towed a trailer from denver to Sacramento. Trailer is small 7 x14 enclosed trailer with tandem axles and had at the most 1k of payload in it. Any pointers how to beat this? BDS installer gave me info what to do.

Moved your post to its own thread. Please don't reply to other threads/posts if its older than 6 months please.

What change did you do to the gearing when you put the lift on?

Please clarify. Since "idle" is around 650RPM I'm thinking you mean light throttle at this range of engine RPM while in motion?

Does this kit correct for driveline angles? . . . as in tilting the rear axle slightly upward in front etc.? Thinking potential for universal-joint issues here.

Factory stock tires are right around 32", so 35" is ~10% taller. We'll use this later.

This seems a stretch on their part. I can't imagine any part of a lift and tires messing up specific gears in a transmission and leaving the rest alone. Maybe if you went up to 60" tires and were constantly beating the clutches to death in the lower gears . . . ? Sounds to me like they don't know what they are talking about and/or are banking on you not understanding. Going up ~10% in tire diameter as you did makes everything 10% more difficult for your vehicle. Not 200%. Add another say 5% (I'm probably high here) for increased wind resistance from the higher stance and wider tires. Shouldn't be a problem except for speedometer/odometer reading and if you are getting close to your weight and performance limits. Still wouldn't affect individual gears and not others. What is specifically "messed up" about 2, 3, 4, 5, and 6? Are the teeth sad? Are the clutches feeling like they should get a pay raise? If they do get a pay raise will 1 and R want in on that action and sue?

Agree, however, this would be a downside of modifying driveline geometry then bringing the issue to the dealer to support. Right or wrong they are now in the position of supporting something that has a chance of being unrelated to them therefore they may walk into it with shields up right from the beginning.

I can't see how this would have caused additional damage all by itself unless the whole trip was off-pavement or you were beating your truck up the whole way.

What did BDS Installer say to do?

Yeaowzaz thats alot. Well lets see if i can answer all your questions. only thing i tuned was place it in tow haul mode, and adjust tire size on ecu to adjust the speedometer to be as accurate as possible.

BDS has all driveline angles and specs set to factory specs with their lift. apparently i had to register when i bought it for them to help me on this. None the less if they were to pursue any help in fighting with chevy to replace my tranny i might be in same situation again in a yr or so.

After many emails, phone calls and heated conversations with chevy management i accepted my faith and pull the trigger on a Monster Transmission. Now just have to wait for the tranny to arrive and get it installed.

As for idle driving, yes i meant keeping a constant speed or cruise control. Once the rpm needles gets between 1500 and 2000 rpms the vibration/shutter happens. Lately ive been using the manual shift button and i try to keep it above 2000rpms to avoid any vibrations. maybe i need to regear axles or something to avoid this again. I use my truck for everything, towing, cross country driving to jobsites,, pulling disker on my property to till up the land, hunting, offroading. Just very disappointed that chevy black listed me on their national database with my truck, even though they sell trucks with my same lift and size tires. no bueno

ok so here/* the recent update since i've return from Hawaiis project. I pulled the trigger on a Monster transmission, had the dealer install it, reflash computers and i still have the same shuttering. Im beyond pissed now. This leads me to believe its 1 of 2 things, driveline or tcase. Its staying at my local dealership, they even admitted that they dealership in sacramento shouldn't have blacklisted my truck by voiding powertrain warranty. Now the new can of worms begins monday to see if the tcase is the issue. Advisor said might be stuck in 4wd some how.
So now i have a oem tranny in bed of my truck thats just fine and after market one installed. Im in Riverside CA if anyone knows anyone reliable that i can go to incase i hit another brick wall.

Thanks, hope to get it back this year.

Wow what a nightmare experience to have to go through.
I always remember a good mechanics statement re drive lines/vibrations....
"If it'* not the transmission chances are it is the transfer case"
My favorite reply would be yes but.. "did you check the drive shaft balance"?
Let'* hope they get this sorted out & Please keep us posted how it goes, & if the t-case was indeed the issue!

The part that gets me is the 1400-2000 thing. It wouldn't likely be anything behind the engine is it only happens at certain engine speeds. I'm thinking weird things like: Taller tires+same gear ratio=engine slightly slower at same MPH when AFM kicks in. I've had some rentals with the same driveline 2011-2017 in which I've toyed with the AFM. About half of them you can get at just the right low speed at very light throttle and get it to go to V4 mode. Back off the throttle a tiny little bit and it will still try V4 mode for a bit until it gets too slow to allow V4 mode. Right on that edge it starts to "thrum" just a little and you can hear it all around. It'* like they could have had V4 mode work even slower but for the harmonic issue. When it is doing this, give it a slight bit more pedal and it goes to V8 mode and the thrum is instantly gone without shifting gears or anything else.

I wonder if the dealer can temporarily disable AFM for you to try out?

Then perhaps lower gear ratio to compensate for the taller tires and/or keep AFM turned off . . . ?

Do you have the stock-size wheels/tires around? You could switch to them to see if the problem changes or disappears.

i dont have truck in my possession, but you are right on the money about the v4 activting or atleast the RPMs coming down low to do that thrummmm noise. i placed it in manual shift mode a few times coming back from sacramento while on the freeway. i would just make sure to keep the rpms at 2k. So far the local dealership is leaning towards my transfercase being some how locked in 4wd Hi. never heard of that but thats where they are going. on another note i call GM and started a ticket regarding getting back my warranty on the grounds of dealership making false or incorrect diagnosis.