Update to my "chevy shake" 6/30/17 (got it back)

M1ck3y · October 9, 2020

If you have rpm fluctuations/vibration get the transmission flushed with the new fluid. There's a tsb regarding this issue, make sure the dealer is aware of it. If the flush doesn't fix the issue, the next option is having the valve body replaced, and after that the torque converter. No improvement after that, your sol.

I experienced rpm fluctuations around 50-150, with a vibration peaking at the height of the fluctuation (rumble strip feel), vibrated in steering wheel.. The speed varied but was most noticeable on a hill or slight incline with light throttle acceleration. It all Disappeared if I went fast enough or put it in manual mode 1700-2000 plus rpm.

Anything like that is not normal, and its not from exhaust. I have headers with a cat-back. Find the tsb regarding this problem, print it off or email it to the dealer when you book an appt. Tell them this is the damn problem, otherwise you may or may not be dealer hopping to get it fixed.

Edited October 9, 2020 by M1ck3y

lucas287 · October 9, 2020

1 hour ago, M1ck3y said:

If you have rpm fluctuations/vibration get the transmission flushed with the new fluid. There's a tsb regarding this issue, make sure the dealer is aware of it. If the flush doesn't fix the issue, the next option is having the valve body replaced, and after that the torque converter. No improvement after that, your sol.

I experienced rpm fluctuations around 50-150, with a vibration peaking at the height of the fluctuation (rumble strip feel), vibrated in steering wheel.. The speed varied but was most noticeable on a hill or slight incline with light throttle acceleration. It all Disappeared if I went fast enough or put it in manual mode 1700-2000 plus rpm.

Anything like that is not normal, and its not from exhaust. I have headers with a cat-back. Find the tsb regarding this problem, print it off or email it to the dealer when you book an appt. Tell them this is the damn problem, otherwise you may or may not be dealer hopping to get it fixed.

I don't have RPM fluctuations though. I consider myself a very well educated and analytical person. I've reviewed several hours of data logs sifting through diagnostic data and there isn't anything (that I see) that points to this being a transmission issue. The vibration increases with engine load between 1500 and 1900...period. TCC slip is very minimal and my TCC line pressure isn't doing anything weird. RPM's are rock solid. Do as much research as I've done then tell me otherwise.

Also, I already had the flush TSB done, problem still exists.

Edited October 9, 2020 by lucas287

lucas287 · October 9, 2020

1 hour ago, M1ck3y said:

Anything like that is not normal, and its not from exhaust. I have headers with a cat-back. Find the tsb regarding this problem, print it off or email it to the dealer when you book an appt. Tell them this is the damn problem, otherwise you may or may not be dealer hopping to get it fixed.

With headers and a cat-back you've likely eliminated the resonation issues with the stock exhaust. With the exception of the side branch resonator I built, my exhaust is bone stock from the manifolds to the tip.

GM has to strike a very delicate balance of emissions, noise, vibration, harshness, performance, etc.. There are inherent trade-offs when developing these exhaust systems and I think that resonance is an unintended consequence. Look at the case of the freaking Lexus RX350! I'm certain Lexus spends more time on NVH than GM does for Silverados. Yet, one of their big sellers STILL made it to production with these issues. But at least they eventually came out with a TSB to address it. GM sold a shitload more K2XX trucks and therefore would never acknowledge the existence of this problem and release a TSB. That's a huge expense.

Edited October 9, 2020 by lucas287

M1ck3y · October 9, 2020

50 minutes ago, lucas287 said:

With headers and a cat-back you've likely eliminated the resonation issues with the stock exhaust. With the exception of the side branch resonator I built, my exhaust is bone stock from the manifolds to the tip.

GM has to strike a very delicate balance of emissions, noise, vibration, harshness, performance, etc.. There are inherent trade-offs when developing these exhaust systems and I think that resonance is an unintended consequence. Look at the case of the freaking Lexus RX350! I'm certain Lexus spends more time on NVH than GM does for Silverados. Yet, one of their big sellers STILL made it to production with these issues. But at least they eventually came out with a TSB to address it. GM sold a shitload more K2XX trucks and therefore would never acknowledge the existence of this problem and release a TSB. That's a huge expense.

Your not the only know it all on here. If that vibration has has been there new, you should have taken it back. If not there's something else going on and whatever's causing the vibration hasn't completely failed yet. Aside from that, maybe your to sensitive to these things. By the way my truck didn't come from the factory with full exhaust. Obviously it makes more noise and vibrations then before and I like it. And I can tell the difference between abnormal mechanical vibration and exhaust vibration because I know my truck.

If you have a vibration that increases with rpm and load, there's something wrong with your engine. The ecm will let you know when it breaks though, be sure to keep an eye out.

Missed the rpm window. Thats no different then what my truck did, it happened between 1400 and 1700 for me. At first it didnt vibrate at all, it was just intermittent fluctuations, then it eventually fluctuated all the time, then it started to vibrate. dealership wouldn't do anything when it was just fluctuating. Again, eventually I found the tsb, highlighted that diagnosis isn't needed beyond customer complaint and they finally did the flush.

If you read that tsb you'll see that if its not done exactly as written it may not provide a satisfactory result. I would try getting it flushed again, and go to a different dealership.

Edited October 9, 2020 by M1ck3y

lucas287 · October 9, 2020

1 hour ago, M1ck3y said:

Your not the only know it all on here. If that vibration has has been there new, you should have taken it back. If not there's something else going on and whatever's causing the vibration hasn't completely failed yet. Aside from that, maybe your to sensitive to these things. By the way my truck didn't come from the factory with full exhaust. Obviously it makes more noise and vibrations then before and I like it. And I can tell the difference between abnormal mechanical vibration and exhaust vibration because I know my truck.

If you have a vibration that increases with rpm and load, there's something wrong with your engine. The ecm will let you know when it breaks though, be sure to keep an eye out.

Missed the rpm window. Thats no different then what my truck did, it happened between 1400 and 1700 for me. At first it didnt vibrate at all, it was just intermittent fluctuations, then it eventually fluctuated all the time, then it started to vibrate. dealership wouldn't do anything when it was just fluctuating. Again, eventually I found the tsb, highlighted that diagnosis isn't needed beyond customer complaint and they finally did the flush.

If you read that tsb you'll see that if its not done exactly as written it may not provide a satisfactory result. I would try getting it flushed again, and go to a different dealership.

Hey I'm hardly a know it all

When two gearheads convinced in their own ways share their opinion it seems like I'm being argumentative. (So much harder to convey over a forum vs in person)

I hear yah but it's not fluctuating! At all. It doesnt increase with rpm. Only in that window and only worsened by load.

I've only owned the truck tor 7,000 miles. I've built many engines and several street trucks and cars since my first truck in high school. I'm definitely sensitive to little details! Maybe more so as I age too haha

At the end of the day we are entitled to our own opinions and beliefs. And we're here in a public forum to learn and solve problems, so I appreciate your input.