22 Trail Boss LT 5.3 vibrating/shaking?

22TBossTX · Mar 30, 2022

Hi all,

I have a new 22 Trail Boss LT with the 5.3 that's just coming up on 3k miles. At highway speeds (and sometimes at under) I notice a vibration that you feel in your seat and maybe your feet on the floor board like the truck is shaking. Feels like unbalanced tires/wheels - but I don't think that's it - my stock 20s with stock tires did it, threw some Ridge Grappler tires on the stock 20s and had them road force balanced, still did it. Decided maybe I made the problem worse by going to a stiffer 10 ply tire while on 20" wheels (smaller sidewall) so decided to trade the wheels/tires out for 18" aftermarket wheels with 295/70r18 tires - which I also had road force balanced. Still does it.

It's weird - I find certain speeds or stretches of road where it's not as bad, and then it'll get bad for no rhyme or reason - I guess I need to drive it some more and study when it's doing the worst. I don't really feel a shimmy in the steering wheel - just seems to be the bottom side of the truck vibrating or bouncing.

I've already got a service appointment scheduled to get the rear doors aligned (they don't shut properly and when you do shut them as hard as you can, you can tell when you open them that they weren't latched properly, just feels like they pop open without a full pull of the door handle - like the properly aligned front doors do). I guess I'll add the shake/vibration to the list... I still have the stock wheels/tires in the bed of the truck so the dealership can throw them on and see it's not the aftermarket wheels/tires causing it. Dreading going down this path as I just went through a saga of 2x lemon 22 F250s in a row.

Looking for any insight or suggestions. Thanks

22TBossTX · Mar 30, 2022

I forgot to add that I also put a Readylift 1.75" leveling kit on it with replacement upper control arms. I know the truck had the vibration before the suspension/wheel/tire changes - but wondering if I made it worse. I wish it was easier to pull the leveling kit off and check the ride for comparison, but I lack the proper equipment to do this easily.

Ikaika · Mar 30, 2022

It's the 4 cylinder shutoff. I've been in your seat, don't bother with the expensive transmission fluid or any of that. Grab the Pulsar LT or comparable item to kill it and the shudder will go away.

brewtus · Mar 30, 2022

Ikaika said:
It's the 4 cylinder shutoff. I've been in your seat, don't bother with the expensive transmission fluid or any of that. Grab the Pulsar LT or comparable item to kill it and the shudder will go away.

Yes. Or drive it in L9 so it doesn't kill cylinders and it is smoother too.

22TBossTX · Mar 31, 2022

How do you drive it in L9?

brewtus · Mar 31, 2022

22TBossTX said:
How do you drive it in L9?

Move gear selector in "L" instead of "D" - use the up down buttons until it shows 1 less than the speeds in your trans. If 8-speed - L7, If 10-speed - L9.

Keeps it from going into AFM or DOD modes......

Jmac49 · Mar 31, 2022

brewtus said:
Move gear selector in "L" instead of "D" - use the up down buttons until it shows 1 less than the speeds in your trans. If 8-speed - L7, If 10-speed - L9.

Keeps it from going into AFM or DOD modes......

2021 TB 6.2L.....I've been waitng on this statement. What is the difference between L9 and L10 ?? I find no difference at all. Both disable auto-stop and seems to defeat the DFM. Same "heavy" feel that shows on L9.

brewtus · Mar 31, 2022

When driving in the "L" or manual modes 1 less than the number of speed in your transmission it defeats the deactivation of cylinders. I used to drive my '16 GMC with the 5.3 8 speed in L7 frequently because it vibrated in "D" mode letting it go into 8th gear when the AFM kicked in. my '07 with AFM had the v4/v8 indicator in the DIC and was smooth as silk. Couldn't even tell unless you were looking at that indicator.

Wakinvol · Mar 31, 2022

I

brewtus said:
When driving in the "L" or manual modes 1 less than the number of speed in your transmission it defeats the deactivation of cylinders. I used to drive my '16 GMC with the 5.3 8 speed in L7 frequently because it vibrated in "D" mode letting it go into 8th gear when the AFM kicked in. my '07 with AFM had the v4/v8 indicator in the DIC and was smooth as silk. Couldn't even tell unless you were looking at that indicator.

I’ve got a 2014 Silverado Crew 4x4 with the 5.3 as my work truck. I notice the swap from v-8 to v-4 frequently. I personally hate it but it’s hard to complain about free. Does this manual mode work on that model too? I may give it a shot. It’s got almost 180k but it’s still a great truck…other than the AFM.

22TBossTX · Apr 4, 2022

Appreciate the tip about L9 & DFM/DFM. I went ahead and put my stock 20" wheels and stock Goodyear MT's back on - had them road force balanced at Tire Link (if you're in the Houston area - can't say enough good things about them, won't ever go to Discount Tire again) and the truck rides great. The stock Goodyears are loud, but the truck doesn't shake even at 80+mph.

At least I know my truck doesn't have some kind of issue causing a vibration and that it was all tire related. I got scared when I started researching and found all of the 'chevy shake' references.

Now I'm back to needing some tires, the 265/60r20s or whatever it came with look too small for the truck even before the level. I'm thinking about just putting some 275 or 285 / 65r20s on it and keeping the stock wheels since they are hub centric and I don't have to deal with hub centric rings for aftermarket wheels.

Is everything in a 275 or 285/65r20 going to be E rated 10 ply? Not looking forward to the diminished ride of a much heavier / stiffer tire so thinking about trying to find a middle ground.

Tokolosh · Apr 4, 2022

22TBossTX said:
Appreciate the tip about L9 & DFM/DFM. I went ahead and put my stock 20" wheels and stock Goodyear MT's back on - had them road force balanced at Tire Link (if you're in the Houston area - can't say enough good things about them, won't ever go to Discount Tire again) and the truck rides great. The stock Goodyears are loud, but the truck doesn't shake even at 80+mph.

At least I know my truck doesn't have some kind of issue causing a vibration and that it was all tire related. I got scared when I started researching and found all of the 'chevy shake' references.

Now I'm back to needing some tires, the 265/60r20s or whatever it came with look too small for the truck even before the level. I'm thinking about just putting some 275 or 285 / 65r20s on it and keeping the stock wheels since they are hub centric and I don't have to deal with hub centric rings for aftermarket wheels.

Is everything in a 275 or 285/65r20 going to be E rated 10 ply? Not looking forward to the diminished ride of a much heavier / stiffer tire so thinking about trying to find a middle ground.

I think your stock is P275/60R20 so you'll get another inch if you move to P275/65R20. You might be able to fit a P285/65R20 on the stock rim and avoid rubbing but there might be a little trimming for full turn.

Tire Size	Width In.	Height	Wheel Diameter
P275/65R18	10.8	32.0	18
P275/70R18	10.8	33.1	18
P295/70R18	11.6	34.2	18
P295/75R18	11.6	35.4	18
P275/60R20	10.8	33.0	20
P275/65R20	10.8	34.0	20
P285/65R20	11.2	34.6	20
P295/70R20	11.6	36.2	20

22TBossTX · Apr 5, 2022

My stock Goodyear MT's are 265/60r20s. I think I'm going to try some Recon Grapplers in 275/65r20. Will reply back with how they work out.

Gmtrucks · Dec 18, 2023

You can fit the 285 65 r20s on stock. I went up from. I have a stock 2022 Silverado LT Redesign z71 and towing package. The GM lift I have is still in the garage. Only rub I get is when I am in full lock reverse