2012 volvo vibration

Ok , i drive 2012 volvo with Ishift and 343k miles on it.

A week ago i noticed vibration while going uphill. Whole truck was shaking,like going over rumble strips.

It mostly happens uphill, between 1000-1400 rpms. While truck shakes, rpm needle shakes as well, nothing wild, but i can see its jumping a little bit.

If i let off the gas pedal, vibration is gone.

I changed fuel filter,still the same.

The other day, while on delivery, i was checking cables and wires on the batteries.

I moved them around , but everything was tight.

Afyer that, on my way to the shop, vibration was gone.

They test drove it and couldn't find anything wrong.

Today i took the load, and after 200 miles truck started to shake again.

Its all good on flat ground, no vibration. It starts to shake uphill when rpms drops under 1300-1350, and again, if i let of the gas, shake is gone immediately.

All tires are new and aligment is done.

Any ideas? Could it be that there is something wrong with those wires on batteries?

 

Its d13 volvo. It uses DEF. No check eng light or any other light.

Fuel mileage is not great. Right now 6-6.5 with 40000 lbs.

I only got this truck for two weeks so i dont know is it normal or bad. My first trip i got 7 mpg with 39000 lbs.

Im my case everything is normal till i go uphill.

Idle is normal too.



This fuel filter is 5 days old. Should it look like this?

 

No i haven't. How can i check it?

 

I can't see any fuel in the fuel filter. Normaly there should be,right? And the bottom of the filter looks dirty.

 

Was your fuel filter dirty like mine on picture above?