Truck is hopping and snapping -- getting worse

[JeepingNet]

I'm having two odd problems with my Power Wagon, which I feel might be related -- Been there since the day I got it but I feel them much worse after a year.

Dealership says two things:
1. They don't feel anything
2. The tires (the first issue was 100% there before I swapped the tires) -- I do understand where they could say the second issue is tires but never had tire issues feel like this..


The first issue is the clunk you feel in the seat and hear when going from 2nd to 1st to a stop. My kids even comment on it in the back seat. It doesn't always happen but it does happen about 20% of the time.
I thought perhaps this was normal when I bought the truck but while the feeling has stayed the same the sound is more noticeable. I do wonder if this might be a loose control arm..

The second issue, the one I'm more concerned about, is when going up a hill, if I leave a constant acceleration -- not fast, just small constant -- the truck will start to lurch up and down. It isn't axle hope I've had lots of leaf-sprung Jeeps it isn't that in fact it feels like it is coming more from the center of the truck. This issue is getting much worse to the point the truck feels unsafe or something is going to snap. It feels similar to when I've had a bent driveshaft but what that you'd feel it all the time at speed.

I suspect it is a driveline or transmission. My next step once the snow is gone is I'm going to strap a GoPro to several positions under the truck and see if I can reproduce the issue and see anything.
I'm very familiar with owning trucks and Jeeps. I also own a LJ Rubicon on 37s and have owned many other Jeeps all lifted and on bigger tires.

Thoughts?

 

[Kauffmj1]

My 09 GMC would do the same thing going from 2nd to 1st and after lots of asking I basically got a "That's just what they do" sort of answer. On a newer trans like the ZF8, is there any kind of reflash or relearn the dealer can do? I know dealers are fairly unhelpful unless they can replicate the issue, but might be worth an ask.

The second issues has me thinking tires. Maybe a tossed wheel weight or something like that. It would be an out-of-pocket expense, but maybe have the tires balanced at a good shop just to eliminate that as a possibility.

Is it a specific speed or RPM the feeling starts? If so, that could be something harmonic like an out of balance driveshaft. I'm guessing since the dealer hasn't helped, its not something you can replicate by holding the speed at 35mph or the RPMs at 2500 or something like that?

 

[areuriding]

The clunk your having is trans, I have a Hellcat Redeye and it has the ZF8. This is a well known issue in the Hellcat forums. Most are solved with the trans being re-flashed. Mine had that exact issue and after several trips I finally talked the dealership into doing a re-flash just to satisfy me. Well what do you know, problem solved. I'd try that route and see where it leads. This will hopefully solve both issues.

 

[Wobly]

The 2nd to 1st (or 3rd to 2nd) downshift clunk is very common with the ZF8 transmission. I told the dealer about it, they reflashed the transmission and it went away.
As for the hop you are describing, I am guessing that you are driving off-road and have your tires at road pressure. What do you have them at? For reference, I have Falken AT3Ws 35's and run 45 psi front, 40 rear. When going off-road, I lower them to 18 psi all around. Try lowering your tire pressure and run the hill again.
If you mean you get the hop on things like concrete seams on the highway, that is my issue, too. The seams in Colorado are spaced just right to get the harmonics rocking the truck.

 

[Gadgetech]

Guess I’ll ask my dealer to do a reflash for me as well. Got my new PW yesterday and I noticed it. Seems to happen more frequently when I come to a stop more quickly rather than gradually slowing.