2011 Tundra Sport Suspension "Sticky"

I installed new higher rate rear springs, which helped the ride height for the load I usually carry. But, when trying to measure the "sag", after I push down on the rear of the sled, it doesn't rise up to the free height as when I lift on the sled.

I checked the suspension bolts, everything seems fine, I lube the suspension often.

Is it normal for the suspension not to rebound back to the free height after being pushed down, or does it have too much friction?

2011 Tundra Sport Suspension "Sticky"