[tronchsr]

First off, been a member a long time - love reading all of the many repair discussions - hate the look and V6 Turbo of the newbies!
** 2012 Super White w/ Red Rock Interior, CrewMax 5.7L/FlexFuel (purchased new Jan 2012 and added TRD true dual exhaust & rear TRD sway bar - have been running all-terrain 305/55's on the stock 20" wheels ever since the stock Bridgestones were sufficiently worn, and 4Whhel Parts leveling kit approximately 1.5 inch lift <&> currently125,000mi) **
On my recent road trip to the Ozarks of Missouri & the Mark Twain National Forest, while driving the sharper of the curves my front end began bucking/pulsing. Most times without the brakes applied, but the also with the brakes applied and I could feel the anti-locks pulsing in through the brake pedal. I frequently drive using Shift Mode, and gradually down shift prior to applying the breaks. I.M.O. helps improve fuel mileage; but also sounds great with the duals and even better with the windows down
Anyway, all trips were on dry roads, average temperature was in the high 60's. The highway I was traveling was posted for 55mph where I frequently drive 5 or so MPH above the posted limit; many curves were speed rated at 40mph, 35mph, some even 30mph with an occasional 25mph. Although this should not be a problem and most can be taken between the lines at nearly 10mph above this limit, most of the curves were taken at or just above (3-5mph) the posted speed rating - the truck's front end began pulsing/bucking/grinding with and without the brakes applied. On one of the 1.5 hour long outings I switched the traction control off for the whole trip and had the same results. The problem also occurred on one of the outings while towing a lightweight 18' trailer containing two 4-wheelers using TOW/HAUL mode. The only other time I have ever experienced the severe shaking/bucking/pulsing in the front end was several years ago when braking hard at 75mph due to a small herd of deer jumping in front of me - missed them and scared the crap outta me and my passengers; honestly the anti-lock break shudder was more alarming to me -but they worked!
This dry road shuddering during very mild driving conditions does not seem normal and is very troublesome. My questions regarding this: possible causes? what to check? potential malfunctions?

Thanks in advance!
TRONCHSR

 

[Blenton]

Did the traction control light on the dash flash at the same time as the bucking/grinding noise? Trying to verify that the vehicle meant to engage vehicle stability control.

If the light was flashingand the vehicle purposely engaged the ABS, there a few - mostly simple - things that it could be. You could have a wheel speed sensor on the fritz which would be my first guess.

A close second would be the need for a Zero Point Calibration reset. There are instructions on the site here on how to perform it. I’m assuming you have a leveling kit of some sort to fit that size tire which takes the vehicle out of the stock calibrated body level position. There are some sensors under the center console that determine vehicle pitch; if they go too far one way or the other, the vehicle thinks is being unsafe and you could lose control (such as rolling the vehicle) and the stability system is engaged.

Third would be tires. If they are fairly wornyou could be actually be losing traction in the corners on dry pavement. If memory serves, even at 4/32” tread depth you are losing some 20% of grip over tires with 8/32” or more. They could also be under inflated - especially if filled to the pressure on the door placard which is incorrect whenever you change tire size - and they are rolling over the bead on hard corners. Being such a wide tire, this is quite likely. They could be contacting things like upper ball joints and actually be the source of the bucking/jittering. When I ran 275/70r18’s, they would contact the skid plate on slow turns at full lock if aired up to the door placard pressure.When properly aired up per the inflation table for that tire size, I never had a problem.

I also like to corner aggressively on certain windy roads I’m very familiar with. Rarely has my Traction control kicked in, but on the few times it has in those situations - it’s been for good reason…

 

[tronchsr]

Thank you for the response. I appreciate all of the suggested possibilities. I never noticed the traction control/ABS/vehicle stability control light flashing during any of the felt troubles.

- Of them all, I am inclined to pursue the second of your suggestions - Zero Point Calibration - as it seems most logical to me. I have not seen specific instructions that I can remember seeing; but I am going to look/search for them here next.

- My tires are barely 20% worn and look new; although I do not have a tire tread depth gauge. I aired the tires to 48psi front and 45 rear prior to the 5 day trip (no significant temp variations day/night other than highway cruising and distance traveled ~4.5 one way at the beginning and end of the trip). I considered this as well and checked them when I returned home still 48 & 45. The max rating for these Falken AT3's is well above 50psi per the sidewall rating (I think it says 65psi MAX). Prior to adding the lift and early on in running the 305s I had the rubbing problem on the skid plate only - which I resolved with slightly modifying the stock skid plate by rolling the far outside edge of the skid plate in about an inch-n-a-half. Even without the lift provided by the leveling kit, I never had any rubbing problems .... Rubbing problems create a very distinct sound and a much more rapid grinding noise than the shuddering/grinding sound I was experiencing.

 

[Blenton]

You are welcome. Sounds like you know more about your own vehicle than most do, which is great. Makes it easier to cross items off the list and try to narrow things down. Nobody needs to walk you through how to check your tire pressure 🙃 Unfortunately, that rules out blinker fluid and muffler bearings… 😖

One other thing I thought of - before looking for more expensive and involved repairs - is the rear leaf springs. Mine had a significant amount of axle wrap from being used pretty hard. Perhaps a downshift upset the balance of the vehicle as you were braking and turning with much of the vehicle weight shifted forward. I’ve had this happen on patchy winter roads before; it caused the back end to hop a bit and felt like ABS engaging as the tire would grip and slip sputteringly, eventually engaging the ABS until the wheel speeds all nominalized. I realize you are not on patchy winter roads but small gravel on the side of the road can cause similar behavior. Gravel on the side of the road is prolly the number one cause of traction control engagement on my truck - at least it was until I installed an Auburn. Now much of it has been mitigated. But I also know that when driving aggressively on corners, I use as much of the road as possible to hit the apex of each corner. . Cuz I pretend I’m a racecar driver sometimes. Like I said - just another idea.

 

[tronchsr]

Yes, exactly! I topped off the blinker fluid and replaced the muffler bearings on both mufflers of the duals prior to this trip . . . .