Grinding Noise and Vibration

JeremyTaylor · March 24

2017 Silverado double cab 4x4, I changed the rear gears so I can only drive in 2wd until I get the front ones changed. it has a 9 inch Mcgaughy’s lift on it. am having a grinding noise and it sounds like it’s coming from under the front area. It happens when I am pressing the gas and staying at the same speed. Say If I am going 35 and I am lightly pressing the pedal to stay around that speed I hear a loud grinding and vibration. If I let off the gas it stops, if I press the gas harder it stops.
I really need some help with this. I can’t figure out what the problem is.

CamGTP · March 24

Could be front driveshaft related but hard to say. You could unbolt the driveshaft and test it again.

JeremyTaylor · March 24

Can you drive it without a front driveshaft?

CamGTP · March 24

I believe you can unbolt it from the front diff and just hang/tie the driveshaft up because you can't technically remove the shaft from the transfer case without leaking fluid out.

If the transfer case is in 2WD, it shouldn't spin the shaft.

JeremyTaylor · March 28

I removed the front drive shaft and tried that. Still doing the same thing. I noticed when driving it happens at low rpm’s at a steady speed and the rpm’s jump when it happens.

mikeyk101 · March 28

RPM jump leads me to think of transmission related. Possibly torque converter? both of those are weak points on these trucks. How many miles are on your truck and do you have a 6 or 8 speed trans?

JeremyTaylor · March 28

140,000 and 6 speed. It’s the 6l80 transmission.

mikeyk101 · March 29

4 hours ago, JeremyTaylor said:

140,000 and 6 speed. It’s the 6l80 transmission.

Mine which is on my 2016 is also a 6L80 and just failed at 96,000 miles. And if you search through this forum, you will find many other 6L80 failures as well. According to what I have found, GM is aware of the problem and just chooses to ignore it. Surprisingly, mine gave no warning that it was failing. Although I tend to have the tunes on all the time while driving so maybe I just didn't hear it. I do recall the rpms jump a little on a few occasions but nothing that seemed out of place.

Many have said that the torque converters on these are a poor design and a disaster waiting to happen. If you catch it soon enough before the torque converter fails, you can probably save the transmission. when it fails, it sheds all kinds of metallic shavings into the transmission and then you have no choice but to rebuild it replace it. You can tell if this is happening by dropping the transmission pan and seeing if there are any metal shavings in there. If you're lucky, you won't find any and then think about replacing torque converter with a quality aftermarket one. Some have suggested getting a billet one.

Just wanted to add, my 2016 is still covered by the GM Protection Plan. It saved the day a couple weeks ago when my trans failed and they covered the replacement. Because of this, I have only done mild mods to mine. But I was warned that if during inspection if I had oversized tires (mine are just 275/60R20 instead of 275/55R20 so a slight oversize) and/or lift kit, they would have voided my plan and denied the approval to fix. I was told that oversized tires and lift kits put too much strain on the drive train. I'm guessing though that you have no warranty coverage so repairs are on you. But with you re-gearing I will bet that helps some...