The Payload on these trucks is known to be quite bad. Speaking from experience the stock coils sucked at handling weight. I had 900-1000 lbs of gear on my first long overland trip in the bed with stock coils, and interstate driving was miserable. Also towed around 5k and also not a fun experience. I will say some timbren bumpstops helped tremendously with payload and towing. I now have superlift SL-140 rear coils and it hauls and tows like a dream now.
Pics:
This is stock springs and not even a lot of wood and you can see the sag.
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This is stock springs and maybe 2500 total lbs of trailer weight. (loaded correctly) and she was sagging.
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Here's the start of the aforementioned overland trip
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Here you can see close to the same overland gear with the new SL-140 springs
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