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Forest River Sandpiper 3660MB

Fifth wheelbuilt 2021–23Mixed build tierFindable on the used market
WHAT ONE COSTS
$55,000est. used (2023, 3 yr old)

Sticker was $88,846 in 2023. Out of production since 2023, so the used market is the only way to buy one. Estimate assumes a 2023 unit.

WHAT IT WEIGHS BEHIND YOUR TRUCK
~12,876 lbestimated as towed, for 2 people

dry weight 11,659 lb + fresh water (50 gal, full) 417 lb + propane + battery 200 lb + gear for 2 600 lb. Brochure dry weight omits water, propane, batteries and your gear; this estimate doesn't.

You want a tow rating around14,310 lb (10% margin)
GVWR (the sticker maximum)14,115 lb
Tongue weight, loaded~2,336 lb (18%)
Cargo capacity2,456 lb
WHICH TOW VEHICLES IT FITS: 19 OF 95

Judged the way the app judges: estimated loaded weight against each vehicle's rating less a 10% margin, per model year, because the 3660MB's published weights changed mid-run. Fifth wheels also need a pickup bed and are held to the fifth-wheel rating where published.

VEHICLETOW RATINGVERDICT
Chevrolet Silverado / GMC Sierra 2500HD (Duramax, max tow) '24-2622,500 lbfits, loaded, with 10% margin
Chevrolet Silverado / GMC Sierra 2500HD (Duramax) '20-2318,510 lbfits, loaded, with 10% margin
Chevrolet Silverado / GMC Sierra 2500HD (Duramax) '11-1918,100 lbfits, loaded, with 10% margin
Chevrolet Silverado / GMC Sierra 3500HD (Duramax DRW, gooseneck) '20-2636,000 lbfits, loaded, with 10% margin
Chevrolet Silverado / GMC Sierra 3500HD (Duramax DRW, gooseneck) '11-1923,300 lbfits, loaded, with 10% margin
Ford F-250 Super Duty (6.7 diesel, gooseneck) '20-2222,800 lbfits, loaded, with 10% margin
Ford F-250 Super Duty (6.7 diesel, tow pkg) '17-1918,000 lbfits, loaded, with 10% margin
Ford F-250 Super Duty (6.7 diesel) '11-1616,600 lbfits, loaded, with 10% margin
Ford F-250 Super Duty (6.7 HO diesel, gooseneck) '23-2623,000 lbfits, loaded, with 10% margin
Ford F-350 Super Duty (6.7 diesel DRW, gooseneck) '17-1932,500 lbfits, loaded, with 10% margin
Ford F-350 Super Duty (6.7 diesel DRW, gooseneck) '20-2237,000 lbfits, loaded, with 10% margin
Ford F-350 Super Duty (6.7 diesel DRW, gooseneck) '11-1621,600 lbfits, loaded, with 10% margin
Ford F-350 Super Duty (6.7 HO diesel DRW, gooseneck) '23-2638,000 lbfits, loaded, with 10% margin
Ford F-450 Super Duty (6.7 HO diesel DRW, gooseneck) '23-2640,000 lbfits, loaded, with 10% margin
Ram 2500 (6.7 Cummins HO) '19-2620,000 lbfits, loaded, with 10% margin
Ram 2500 (6.7 Cummins) '11-1817,980 lbfits, loaded, with 10% margin
Ram 3500 (6.7 Cummins DRW, gooseneck) '13-1831,210 lbfits, loaded, with 10% margin
Ram 3500 (6.7 Cummins HO DRW, gooseneck) '25-2636,610 lbfits, loaded, with 10% margin
Ram 3500 (6.7 Cummins HO DRW, gooseneck) '19-2437,090 lbfits, loaded, with 10% margin
The 76it doesn't fit

These verdicts assume 2 people aboard with typical gear. See the margin for your truck and your crew →

THE SPECS
Length41.3 ft
Height (incl. A/C)13.3 ft
Width8.0 ft
GVWR14,115 lb
Dry weight11,659 lb
Dry tongue weight2,115 lb
Cargo capacity2,456 lb
Sleeps13
Slide-outs4
Axles2
Fresh water50 gal
Grey water82 gal
Black water52 gal
Awning20 ft

A missing row means the maker never published that figure: unknown, not zero.

WHERE PEOPLE SLEEP
  • 2× Two queen beds - front primary and mid-bunk room(Permanent)60×80
  • 2× Double bunks in the bunk room(Permanent)—
  • 4× Dinette and sofas convert(Convertible)—
HOW IT'S BUILT: 4/5
WallsLaminated fiberglass
FrameAluminum
RoofWalk-on
UnderbellyEnclosed

Forest River (Mixed tier): Forest River's volume fifth-wheel platform - genuinely welded-aluminum laminated construction with mainstream-brand QC, nothing more.

YEAR BY YEAR: WHAT CHANGED
YEARSGVWRDRYMSRP
2021–2214,115 lb11,659 lb$88,846
202314,115 lb11,659 lb$88,846
  • 2021Introduced at 39'11", sleeps 11
  • 2022Sleeps rating raised by two
  • 2023Length stretched to 41'4"; final model year
FINDING ONE

Findable: a few listed nationwide most weeks. Why: Forest River is a volume manufacturer. Estimated from build volume and production span, not a count of live listings.

OUR TAKE

A big mid-bunk family fifth wheel; with 2,456 lb of cargo capacity and a 2,115 lb pin you want a one-ton to use it honestly.

OTHER SANDPIPER FLOORPLANS
2990TRIK · 12,729 lb · sleeps 6321RL · 14,175 lb · sleeps 63220RL · 12,729 lb · sleeps 63330BH · 13,769 lb · sleeps 63370RLS · 13,560 lb · sleeps 43440BH · 14,075 lb · sleeps 83550BH · 15,500 lb · sleeps 83550FL · 13,684 lb · sleeps 6368FBDS · 15,500 lb · sleeps 43710HBFB · 15,500 lb · sleeps 7372LOK · 15,500 lb · sleeps 63738H · 15,500 lb · sleeps 83770FL · 14,175 lb · sleeps 6379FLOK · 14,175 lb · sleeps 6the whole line →
Find one for sale

Live listings for the 3660MB on the big marketplaces. Each search opens pre-filled with this exact floorplan:

RV Trader ↗Camping World ↗FB Marketplace ↗Google ↗

Inventory varies by site and day. Slim pickings? search the whole Sandpiper line ↗

Is the 3660MB your #1, or just a spec sheet?

These are the facts. Whether it beats the other six thousand rigs for you depends on what you care about. Set your priorities as sliders, switch on your hard limits, and watch the whole market re-rank around them. Every exclusion explained, every margin shown.

See where it ranks for you →

Data compiled from dealer and aggregator listings, retrieved 2026-07.