The area where the leaf springs attach to the frame on my single axle RangerTrail trailer are really squeaking every time I hit any type of bump in the road. I was able to isolate it by applying WD40 to various spots while my son bounced up and down on the trailer. However, the WD40 isn't going to last very long (it's already starting to squeak some when I bounce on the trailer), so I'm wondering what the best option is to fix this long term? Do I need to take the nuts and bolts off and apply marine grease to them?