I’m getting a pretty bad vibration that feels like driving over a rumble strip on the highway when I’m coming to a stop at speeds lower that 15mph. It doesn’t matter if the truck is in gear or in neutral I still get the vibration that is steady from 15mph to zero. Even crawling at 1-2mph I feel it. I had the truck garaged for the last 6 months so I’m wondering if my tires developed flat spots or something.

I pulled the drive shaft to check the ujoints and they are smooth and don’t bind in any direction and I grease them while I was at it. I also swapped the 3rd member out not directly related to the vibes, it had a lunchbox locker that I didn’t like so I decided to swap in an open 4:10. There was slop in the pinion on my old diff anyway so I hoped swapping it would be the fix but for the vibrations as well but it wasn’t.

The Front wheel bearing are new I just did them last year and all four wheels spin freely with no slop so the drums and calipers aren’t binding. If it’s not flat spots I’m not sure what it could be? Output bearing on my Tcase? I’ve never had flat spots before either so not even sure what that’s actually like but I get a whomp whomp whomp resonance that feels like it resonates through the whole chassisfrom when I get to around 15mph and under and at higher speeds I guess I hear a resonance to the tires but it drives normal at speeds above 15mph. it feels like I’m on a washboard road at time as I slow to a stop.

anyone have any ideas?

 

How many miles have you driven since it was parked for 6 months?

Just what kind of tires? size type ? Are the tires balanced with weights ??

You did not notice anything when checking for brakes dragging or never looked at the tires .?

The brake bearing surface on the drums and rotors is clean and free of rust that might be enough to cause the issue

I have noticed flat spots even after a few weeks but they seem to get better after 20 miles or so.

This happens at every stop no matter where I have been on some roads the surface is so rough I think I am about to have a major failure.

The first time I crawled under the truck to inspected things.

 

Hmm I guess since I noticed it I only took a couple of short trips one was around town about 10 miles stop and go and the others were short test runs maybe 4-5 miles. I have read that flat spots can correct once the tires warm up with some miles like 20-30 miles so maybe I should take a drive for an hour today or something and see if it helps. I’ve just been concerned that something is going to explode because the vibes are bad but what you describe seems like a similar thing to what I’m seeing.

as far as rust the drums have some surface rust but overall the truck is very rust free I didn’t need any on blast to pull the axles when doing the diff the other day. It’s a Southern California truck.

tires are Dick Cepek extreme country 31x10.5. Apparently they are somewhat of a rebrand of the Cooper STT Pro. They have been good tires so far with about 12000 miles on them.

I have had a load in the back of the truck for a while to help my OME springs settle and to weight the bed down so the locker wasn’t so sketchy driving in the winter so that probably contributed to flat spots.

 

AH Ha just how much weight did you have in the bed?

My truck is empty when I get flat spots after 2 weeks.

A loaded truck sitting for that long flat spots make even more sense.

 

😂 three 50lb bags of gravel. Nothing crazy but I’m sure it didn’t help.

 

Yeah I just confirmed flat spots. I jacked up the rear end and spun the tires and you can see it dip in while the tire is rotating. Going to drive it 50 or so miles and see if it helps.

 

At least you know unknown problems drive all of us crazy

 

I’ve had my fair share of those with this truck but it’s finally getting to the point where some of the usual culprits don’t make sense because they have already been updated with new parts. I’m glad I got this figured out relatively quickly to be honest.

as far as the drive I just took the vibes are still there but I did notice an improvement so I think it’s possible the damage to the tires will correct with some more road time.