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Topic is still relevant. Have an 18 Silverado Z71 LT 18 inch wheels  900 miles and am getting a slight shake in the steering wheel/front end at 70 or so mph. Off to the dealership Saturday...  We shall see.  

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Hey guys I was heavy on this topic not long ago. I left here saying I was going to swap the axles which ended up taking longer than I had wanted. Well I did. I went with an aftermarket axle and while the rear end was opened I swapped from 3.42 gears to 4.10 for my 34" tires. I did stick with AAM gear set.  RPM's on the highway now are a little higher than I wanted  but I have my power back. Anyways I still have the shake just at different speeds now. Im waiting on my updated tune from blackbear for my speedometer to be fixed. Just using gps on my phone now for speed but its approx. 10 mph off at 65mph. Once I have that I'm going to dive back into this and research some more. If vibration is still around the 74mph mark (worst vibes) in my truck then I know its nothing to do with the rotating mass or drivetrain. Now that my driveshaft is spinning faster than normal at highway speeds due to the gearing change. I still strongly believe it is in the TCM tuning inside the trans. Pulsing clutch pressures and valves and such. Blackbear has worked with me in the past and has modified a pressure value in the trans which made the vibration much less noticeable, at least for my situation.

 

Also I have switched out rear shocks, took out my 2 piece driveshaft and had it balanced and was slightly out of spec and corrected. I know it isn't the driveshaft in our trucks causing the problem as some have a 1 piece and others have 2. It doesn't matter if its 2 wheel drive or 4. Also doesn't seem to matter if you have the 6.2 or 5.3, 6 or 8-speed. 

 

Some have replaced torque converters and have had success. Some have just flushed and serviced their trans and it seems to help. I am wondering if some just get a bad batch of fluid in their trans from the factory causing pressure and slippage issues. I will be servicing the trans soon as well.

 

 

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I have 14 Sierra Denali crew cab 4wd, been battling an intermittent shake at 70 + and I don’t mean a vibration it shook like hell. Hitting bumps and entering curves at 70 + speeds would cause the truck to shake and then it would work itself out and get smooth again. I found another thread on this forum with a guy that was having vibration at 70 to 80 and he took it to the dealer and mechanic told him he knew exactly what it was, rack and pinion bushings. The guy said he had it done and it fixed most of it. So what the hell did I have to lose, ordered the bushings and replaced them, it took 80% of my shake out, now it’s still there but the damn thing is drivable without losing my mind. The part # from GM is 84234960. When I dropped my rack and pinion down I saw that it had 4 bushings and GM only sent me two, the reason for that is only two of the four are serviceable, it’s the two on the left side of the rack and pinion. I don’t know if it will help you guys out but it worked for me, good luck.

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Hey Jesse, where ya been?  Last time we chatted you were about to get out of your Ferd and get into an Audi.  Did you do that and if yes how do you like it?  I had an Audi about 100 years ago, about 1980 I think.  As I recall, it was a five cylinder which should have been a clue from the get-go.  Fun to drive but high maintenance, but that was a long time ago.  Anyway, I’m very interested in the 2019 Silverado as it’s supposed to be new from the bottom up.  Especially interested in checking out the magnetic ride option.  We shall see.

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Hi Guys, Just picked up a 2014 Silverado W/T with 37K Miles. Searched through many pages on this thread and mine is a little different. My truck has no vibrations what so ever at 70 MPH+ Smooth as glass (Actually anywhere above 55MPH mine is smooth as glass). Here's where my problems start 25 - 29, MPH 37-39 MPH 47-49 MPH and then sometimes in the 50s.. I have figured out that it will go away a little when I let off the gas.... I doubt it is tires not being  balanced because why would it only do it at those speeds?  I need to take it into dealership but want to have a plan before I do so or have some sort of idea on what this is? any of  you guys find a fix or have similar issues?

 

Wish I would have found this forum before buying. 

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11 hours ago, Rhino4353 said:

Hi Guys, Just picked up a 2014 Silverado W/T with 37K Miles. Searched through many pages on this thread and mine is a little different. My truck has no vibrations what so ever at 70 MPH+ Smooth as glass (Actually anywhere above 55MPH mine is smooth as glass). Here's where my problems start 25 - 29, MPH 37-39 MPH 47-49 MPH and then sometimes in the 50s.. I have figured out that it will go away a little when I let off the gas.... I doubt it is tires not being  balanced because why would it only do it at those speeds?  I need to take it into dealership but want to have a plan before I do so or have some sort of idea on what this is? any of  you guys find a fix or have similar issues?

 

Wish I would have found this forum before buying. 

Hey Rhino, what I would check first is to see if you have any wedges in your leaf spring stack. What they would do is reposition your pinion angle to help get rid of the highway vibe, but in turn, cause an acel and decel shudder, along with vibes at the speeds your describing. ( I had it done and happened to me) I didn't drive highway much, so I had them taken back out. I couldn't stand it. Hope this helps.

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9 hours ago, taps929 said:

Hey Rhino, what I would check first is to see if you have any wedges in your leaf spring stack. What they would do is reposition your pinion angle to help get rid of the highway vibe, but in turn, cause an acel and decel shudder, along with vibes at the speeds your describing. ( I had it done and happened to me) I didn't drive highway much, so I had them taken back out. I couldn't stand it. Hope this helps.

Got ya, So what your saying is they might of tried fixing the (70 MPH + VIBRATION) by putting in the wedges so I don't have the highway shake.  But now I have the  25 - 29, MPH 37-39 MPH 47-49 MPH and then sometimes in the 50s... I wonder if their is a fix for it or not?

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Not sure. I traded my 14' double cab z71 5.3 with 3.42's that had the highway vibe after they basically fired a cannon of parts at the rear end and fixed nothing. I got an 18' crew cab 6.5 bed  (153 wheel base) z71 5.3 with 3.42 and smooth on the highway, but has the low speed vibes like yours. The hard part is to get anyone to admit they feel anything for the slower speeds. Especially since the '19s are coming and redesigned. They are pretty much washing their hands of the 14- 18 Viberados. Best of luck. 

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On 5/18/2018 at 6:45 AM, Rhino4353 said:

Got ya, So what your saying is they might of tried fixing the (70 MPH + VIBRATION) by putting in the wedges so I don't have the highway shake.  But now I have the  25 - 29, MPH 37-39 MPH 47-49 MPH and then sometimes in the 50s... I wonder if their is a fix for it or not?

Your shake showing up  in the low speed range is where torque converter problems often occurs.  I wouldn’t ignore that possibility. 

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So I got a call from GM in TX and the repurchase of my vehicle was denied.  Get this...no reason at all...just denied

and no further options discussed...ZERO...end of call.  BBB stated to call them Monday after 1pm EDT.  Stay tuned,

may have to get into arbitration stage.  Whole process not to take more than 40 days.

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