We just had our axles replaced on our 2007
Bigfoot 25RQ. The stock 3500# axles were sagging and tire wear was uneven. Upgraded to 6000# axles and springs, with all new shackles and greaseable bushings/bolts. Had to replace wheels since new
brakes were 6 lug instead of the stock 5. With 200 miles towed so far, it’s like a new trailer. Porpoising has all but stopped, and side to side rocking is gone. Rock solid. We tow with a Silverado 2500HD Duramax diesel and couldn’t be happier with the results. IMHO the stock axles aren’t up to the job on a trailer that heavy. Happier trails!