Driveline vibration when hauling

[harpflora]

Hi, I have a 2.5 inch rough country lift on my Jeep TJ.

I had driveline vibrations so I added a 1 inch transfer case drop and it runs fine, no vibrations when it’s just me in the Jeep

However, when I’m hauling 2 passengers in the backseat and have a cargo carrier rack attached on the tow hitch with some items in it. I then get a driveline vibration from 80km/h to 95km/h. It goes away past 100km/h

Could this mean I need to reduce to a 0.5 inch transfer case drop? I assume with the added weight when hauling the Jeep sqauts a little more and changes the driveline angles?

 

[CharlesHS]

I assume with the added weight when hauling the Jeep squats a little more and changes the driveline angles?

You are correct.
I would reduce the transfer case drop spacer to 3/4” and recreate the weight of the passengers and rack; then check for driveline vibrations.
The best way would be to measure the driveshaft and pinion angles with the loaded weight and adjust to get about a 0* difference.