Rough Trailer Towing - XC90 3.2

[Lemsteraak]

My buddy needed a snow, tow, haul the dog to the beach car so I recommended a used XC90 3.2 He is happy overall but says the ride is really rough on his sailing dinghy and trailer. I'm thinking he doesn't have enough tongue weight as his trailer and boat weights about 900 pounds and the tongue weight is around 60 pounds. The line from the trailer winch to the bow eye snapped which would indicate an upward shock loading. His XC90 has approx 160,000 miles and I jumped on his trailer hitch and the rear end seems well dampened.

I understand that there is a Nivomat system that some of the XC90 have, what do I look for and how do you test it? Here is a link to a picture of what the rear suspension looks like, I don't know how to upload pictures to this forum.

https://sites.google.com/site/photos...ys%20XC90.jpeg

Anyone else experience anything like this?