2018 GRAND DESIGN MOMENTUM 399TH

Welcome aboard this used 2018 Grand Design Momentum 399TH, a luxury fifth wheel that blends residential comfort with rugged utility. With a massive garage, spacious living quarters, and Grand Design’s high-end finishes throughout, this toy hauler is built for people who want to play hard and relax even harder.

Whether you’re hauling a side-by-side, motorcycle, or just using the garage as a mobile office or guest suite, this rig is ready for whatever road you take.

Walk up into the main living area, and you’ll feel like you just stepped into a stylish condo:

• Dual opposing slides make the space feel wide open

• Theater seating with heat, massage & LED lights

• Tri-fold sofa for extra guests

• Entertainment center with a large LED TV

• Electric fireplace for cozy ambiance and extra heat

• Solid surface countertops & upscale lighting throughout

This space is made for relaxing after a day of trail riding, boating, or mountain adventures.

The kitchen in the Momentum 399TH is built to handle real cooking, whether you’re meal prepping for a week or feeding a crowd:

• Solid-surface countertops with bar seating

• 18 cu. ft. residential refrigerator (or gas/electric, depending on build)

• 3-burner cooktop with oven

• Microwave/convection combo

• Pantry with pull-out drawers

• Tons of overhead and base cabinets

You’ll feel right at home whether you’re flipping pancakes or firing up tacos after a day outdoors.

Up front is your private master suite, complete with:

• Queen bed (king optional) with underbed storage

• Slide-out wardrobe and dresser

• TV hookup

• Prep for washer/dryer

• Plenty of outlets and USBs for charging all your devices

It’s private, quiet, and comfortable—everything you need to get a good night’s sleep wherever you park.

The main bathroom is laid out with comfort and convenience in mind:

• Large walk-in shower with seat and skylight

• Porcelain foot-flush toilet

• Vanity with solid surface countertop

• Medicine cabinet and towel storage

• Power vent fan

This is not your average RV bathroom—plenty of elbow room and a spa-like feel make daily routines enjoyable.

At the rear is the 13' garage, and it’s way more than just a place for your toys:

• Rubberized flooring with tie-downs

• Happijac bed/lift system with convertible sofas

• Dual entrance doors (garage & patio side)

• Washer/dryer hookups

• Half bath

• TV, cabinetry, and prep for A/C

• Ramp door that converts to a rear patio with rails and awning

Whether you’re hauling gear or turning it into a spare bedroom, playroom, or office, the garage is a multi-use space that adapts to your lifestyle.

The Momentum 399TH is just as impressive outside as it is inside:

• Dual power awnings with LED lights

• Slide-topper awnings (on many builds)

• Outside entertainment center with TV and speakers

• Rear patio with steps and railing

• Massive pass-through storage

• 6-point hydraulic auto-leveling system

• Onan 5.5kW generator (standard or optional)

• Fuel station for toys (30-gal tank)

• Triple A/C units (on many builds)

This is built for campgrounds, rallies, boondocking, or extended stays—it handles it all.

• Length: 43'3"

• Dry Weight: ~15,200 lbs

• GVWR: 20,000 lbs

• Hitch Weight: ~3,300 lbs

• Garage Length: 13'

• Fresh Water: 157 gal

• Gray Water: 78 gal

• Black Water: 104 gal

• Sleeps: Up to 7 (bedroom + loft + garage beds + sofa)

• A/C: Triple 15,000 BTU units (on most builds)

This used 2018 Grand Design Momentum 399TH is the total package: residential luxury, off-grid potential, and true garage versatility. Whether you're full-timing, chasing races, or traveling with toys and teens, this floorplan offers the space, comfort, and flexibility you need.