2026 Grand Design Momentum 399M

New Toy Hauler in Fort Worth, Texas, 76140

$164,995.00

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New 2026 Grand Design Momentum 399M available in Fort Worth, Texas

2026 Grand Design Momentum 399M - New Toy Hauler For Sale by McClain's RV Fort Worth in Fort Worth, Texas features Central Vacuum, Medicine Cabinet, Furnace, Queen Bed, Toilet

2026 Momentum 399M by Grand Design from McClain's RV Fort Worth in Fort Worth, Texas

Unit Specs

Stock #15270
Year2026
ManufacturerGrand Design RV
Make Grand Design
ModelMomentum
Floorplan399M
Type Toy Hauler
Secondary Type Fifth Wheel
ConditionNew
Length44' 10"
Width8' 5"
Height13' 6"
VIN573FM4734TBB04615
MSRP $189,230.00
Sale Price $164,995.00
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Chassis101" Wide Body Super Chassis w/Drop-Frame Storage
Sleeps6
Water Capacity (Fresh)140 gal
Water Capacity (Black)52 gal
Water Capacity (Grey)104 gal
Air Conditioners1
A/C Spec30,000 BTU
Refrigerator Capacity20 ft³
Slideouts3
Payload Capacity4500 lbs
Dry Weight18,000 lbs
Tow/Hitch Weight3464 lbs
# Axles3

Looking to buy a 2026 Grand Design Momentum Toy Hauler RV?

The 2026 Grand Design Momentum 399M is a high-end, large toy hauler designed for serious adventurers who want both massive garage space and full residential comforts. At 44′10″ in length, 13′6″ in exterior height, and with a GVWR of 23,500 lbs, it offers over 19,000 lbs of dry weight—plus a hitch (pin) weight around 3,400 lbs.

Its garage spans about 12′ 6″, letting you haul large bikes, ATVs, or gear. A side patio, third awning, and exterior entertainment features extend the fun outdoors. Inside, you’ll find three slide-outs to expand living space, with an interior height of 8′ 5″ for an open feel. The kitchen features a large island, stainless steel 20 cu ft refrigerator, three-burner cooktop, and full pantry.

On the comfort side, there’s a large front bedroom with queen bed (king optional), a full bath, plus multiple entertainment zones: a 50″ living room TV, 32″ in the garage, and a 65″ TV on the patio. The 399M also comes with features built for tougher conditions: aluminum-cage construction, Weather-Tek insulation package, enclosed underbelly, and heavy-duty axles & tires.

All told, the Momentum 399M is made for those who want both the capacity to haul serious gear and the luxury to live comfortably on the road or at base camp.

View a video of this 2026 Grand Design Momentum 399M RV on YouTube!

2026 Grand Design Momentum 399M Features

Appliances
Electric Heat, Furnace, Microwave, Refrigerator
Electrical
Converter, Solar Prep
Equipment
LED Lights, Smart TV, TV, TV Antenna
Exterior
Awning, Exterior Speakers, Ramp, Skylight, Tinted Windows
Interior/Furnishings
Bench Seat, Central Vacuum, Fireplace, Medicine Cabinet, Queen Bed, Shower, Toilet