Not sure what a 21-footer weighs, but I've got a 23-footer so maybe subtract 10% and see where the numbers are at compared to your tow rating.
23 foot Stellar Lightning ("1/2-ton towable")
GVWR sticker reads 7500 lbs loaded, 5500 lbs unloaded (yeah, right)
- full water (supposedly130 gallons)
- Rhino, one quad inside
- enough food/drink for a week at Pismo (a lot of stuff)
It weighed 9,300 lbs on the axles, plus unknown tongue weight.
If we guesstimate 800 lbs on the toungue, that's 10,400 lbs.
(Thankfully, it's got dual 5,500 lb. axles)
My Expedition, which had a blower, didn't like this trailer too much. Plenty of power, but the trailer manhandled the truck, and this was with two quads but no Rhino. My BIL's F-150 didn't like it much, either.
1. Don't under-estimate the true weight of your trailer. All that crap you pack is heavy.
2. Weight stickers on trailers are meaningless. You won't know the true weight of the trailer you buy until you actually weigh it yourself. But most weight stickers are optimistic on the low side for "1/2-ton towable" toy haulers, if numerous posts on RV.net are any indication.
I have a 19 WW superlight, that I pull with a 06 Dodge ram 1500 5.7 liter.
The truck pulls it well, even up the big hills.
Friend of mine has a 4.6 chevy. I have never used the truck to tow my trailer, but I have driven it around town and the power difference is obvious. It would probably pull, but its going to be slow, and your trans will be working hard.
Used to pull a 21' TH, loaded it was @ 8k pounds. My truck was a 2001 silverado 1500, but I had the 5.3. 3.73 gears. It actually pulled it ok, but if you hit a steep grade and didn't get a chance to get a run up it, you would end up almost downshifting to first at the very top. that little trailer was heavy for what it was. I wouldnt recommend it with the 4.8, although im sure it will do it.