GEN 2 Strange 4A Behavior

[Domin0]

I’ve noticed that when driving on a right-curving uphill road in my neighborhood, usually around 20MPH, that there is an unsettling vibration that feels like it’s coming from the rear end, felt through the wheel and seat. This only occurs in 4A. I have noticed it in a few other cases - always while applying steering input on an incline at lower speeds.

Not because of this, but in the last month I’ve had an alignment, tire rotation & balance, and new leaf spring shackles installed (so the suspension has been checked), with no change to this behavior. Common issue? Normal behavior? Symptom of a deeper problem?

Any guidance would be very appreciated.

 

[smurfslayer]

Do you feel any ‘bind’ in the steering at low speeds; think pulling into a parking space or backing out of one?

 

[Domin0]

Do you feel any ‘bind’ in the steering at low speeds; think pulling into a parking space or backing out of one?

I didn’t think so, but just went for a drive to confirm, and there’s no steering bind from what I can tell. What I did notice though was the same shudder/vibration, more pronounced than normal, now in both 4A and 2H while driving straight up a slight grade at ~20MPH. The roads are wet, if that matters at all.

Edit: I should mention that I have an appointment at my local dealer tomorrow to check the balance again, since nothing they noted on my paperwork a few days ago was accurate. Any additional parts I could/should ask them to check related to this?

 

[smurfslayer]

what is your tire condition like? how many miles? tread wear ? what psi?

 

[Domin0]

what is your tire condition like? how many miles? tread wear ? what psi?

23,000 miles on the original KO2s, 36PSI all around. Tread depth as measured by the dealer two weeks ago was 10, 9, 9 and 8/32" - (and then again incorrectly noted as 11/32" all around last week )

 

[smurfslayer]

hmm... 36 is a bit on the high side, despite what the door placard says. if you have dial caliper, go take a look at the tires.
at the front, check the inside and see if every other tread block is abnormally worn. Measure tread depth at the edges and center. I’ll be the center is a lot less deep.

Even so, 23k is a bit early for the KO2 to manifest poor traction, but, cold KO2’s that have been heat cycled a lot will begin to lose wet weather traction and then dry traction. You’ll notice the rear step out easier and even in 4a you’ll get spinning tires with just moderate throttle.

and now that I’ve re-read your initial post, check the inside of the KO2’s on the rear - you just rotated them for the unusual wear on the inside blocks.

if your truck has the torsen front diff, that does result in some additional ‘pulling’ behavior but not vibration.

you mentioned you had the tires balanced. why?
was it just weights, or did they road force balance? KO2’s are notoriously challenging to get that “perfect” balance that you have when you first buy the truck and tire shops are unwilling to put that much time in it. My original set up had one wheel with something like 14 ounces of weights and the others were close. When the stealership changed my tires and balanced, it wasn’t even close to factory. I had to go to discount tire for a R/F balance to resolve it.

 

[Domin0]

hmm... 36 is a bit on the high side, despite what the door placard says. if you have dial caliper, go take a look at the tires.
at the front, check the inside and see if every other tread block is abnormally worn. Measure tread depth at the edges and center. I’ll be the center is a lot less deep.

Even so, 23k is a bit early for the KO2 to manifest poor traction, but, cold KO2’s that have been heat cycled a lot will begin to lose wet weather traction and then dry traction. You’ll notice the rear step out easier and even in 4a you’ll get spinning tires with just moderate throttle.

and now that I’ve re-read your initial post, check the inside of the KO2’s on the rear - you just rotated them for the unusual wear on the inside blocks.

if your truck has the torsen front diff, that does result in some additional ‘pulling’ behavior but not vibration.

you mentioned you had the tires balanced. why?
was it just weights, or did they road force balance? KO2’s are notoriously challenging to get that “perfect” balance that you have when you first buy the truck and tire shops are unwilling to put that much time in it. My original set up had one wheel with something like 14 ounces of weights and the others were close. When the stealership changed my tires and balanced, it wasn’t even close to factory. I had to go to discount tire for a R/F balance to resolve it.

Thank you for the continued troubleshooting help! Just checked, and as you said, the insides are less deep. The freshly rotated tires on the front are as low as 7/32" in the center, and average 10/32" at the edges.

Had the tires balanced after noticing an abnormal shake in the wheel and pedal at 70+ on the highway, and that seems to have gone away after the balance - trading one vibration for another, I guess. The Hunter website lists my dealer as being Road Force-equipped, and there's quite a variety in the # of weights stuck onto each wheel.

 

[smurfslayer]

We have a lot of variables here. to me, the tires seem like the likely culprit here. It’s entirely possible you could have resolved an issue on the 2 now front tires but left the now rear tire or tires as bad or worse. A quick check would be to move the rears to the front temporarily and see if the steering wheel shakes at speed. If so, start with the tires again.

I run about 34-35 / 32-33 front/rear and I know others go lower in the rear. Another FRF just did the shoe polish test and got to the Raptor Assault recommended 32/28 for full contact patch - and even wear.

Here’s a wildcard: Please check the lug nuts. make sure they 1) attached all the lug nuts. 2) torqued them enough to stay on 3) didn’t over-drive them on with a 500 foot pound impact wrench.

 

[icecoldak]

Make sure your Rear Diff lock is not engaged--I think it disables above 20-25 then comes back on if left on--just a guess!

 

[smurfslayer]

Make sure your Rear Diff lock is not engaged--I think it disables above 20-25 then comes back on if left on--just a guess!

Good point. This can be enabled in 4a...