01 What makes it unique
The 37MD solves the problem long coaches usually ignore: everyone in one room. A dedicated middle den sits between the rear living area and the front bedroom — a second zone for kids, guests, an office or a quiet television — opened by one of the coach’s four slides, and the factory’s eight-berth rating (the highest in the line, shared with the 40DB) follows from it. Outside, two 20-foot awnings run the longest combined shade line in the roster.
The build is the shared platform at nearly full stretch: 12-inch I-beam drop frame, 102-inch wide-body, CoreShield laminated walls, painted front cap, frameless windows, TrussXL truss, limited-lifetime membrane, ThermaShield zero-degree package with the 40,000-BTU furnace, dual 15,000-BTU Whisper Quiet air, tankless water heater, six-point hydraulic auto-level and the mandatory Premium Package with the GE residential suite. The printed 18,100-pound GVWR equals 15,650 dry plus 2,450 cargo exactly, on tandem 8,000-pound axles with 17.5-inch H-rated rubber.
The margins tell the family story honestly: 2,450 pounds of cargo capacity is the second-tightest in the line, and eight occupants’ gear plus a filled 75-gallon fresh tank (about 625 pounds) will spend it — weigh the loaded coach. The 2,705-pound dry pin is one-ton territory outright. Like the rest of the roster, RVUSA’s weight record is the stale early print; the current factory set, brochure-confirmed in June 2026, is used.
02 Full specifications
Dimensions
- Exterior length
- 42' 10"
- Exterior width
- 8' 6"
- Exterior height
- 12' 7"
- Interior height
- 8' 6"
Weights
- Dry / unit base weight
- 15,650 lbs
- GVWR (max loaded)
- 18,100 lbs
- Net cargo / payload (CCC)
- 2,450 lbs
- Dry pin weight
- 2,705 lbs
Capacities
- Fresh water
- 75 gal
- Grey water
- 87 gal
- Black water
- 50 gal
- Refrigerator
- GE 21 cu ft residential
Construction
- Frame
- 12″ steel I-beam · drop frame
- Sidewalls
- CoreShield 2″ laminate · high-gloss gel coat
- Front cap
- Painted fiberglass · clearcoat · LED
- Roof
- TrussXL truss · Alpha membrane (limited lifetime)
Running gear
- Axles (factory)
- 2 x 8000
- Hitch
- Fifth wheel · dry pin 2,705 lb
- Tires
- 215/75R17.5'H'
- LP
- 90 lb total
Galley & systems
- Refrigerator
- GE 21 cu ft residential · 1,800W inverter
- A/C
- 2 × 15,000 BTU Whisper Quiet
- Water heater
- Tankless
- Furnace
- 40,000 BTU
Sleeping & layout
- Sleeps
- Up to 8 (factory)
- Primary bed
- Front bedroom
- Layout
- Middle-den quad-slide — separate mid den between the rear living area and front bedroom, two 20-foot awnings
- Awnings & entries
- 2 · 20′ + 20′ · 1 entry (RVUSA)
03 Bighorn floorplan family
Heartland's Bighorn line — the flagship luxury fifth wheel of the relaunched range: seven 2026 floorplans, every one a 102-inch wide-body on a 12-inch steel I-beam drop frame with a painted fiberglass front cap, CoreShield laminated sidewalls in high-gloss gel coat, the ThermaShield zero-degree package with a 40,000-BTU furnace, two 15,000-BTU Whisper Quiet air conditioners, and a mandatory Premium Package that includes six-point hydraulic auto-leveling, a GE 21-cubic-foot residential refrigerator with an 1,800-watt inverter and a GE appliance suite. All seven plans are profiled in depth on the Bighorn hub with verified weights.
| Floorplan | Nominal | Sleeps | Notable |
|---|---|---|---|
| 31RL | 36 ft | 4 | Rear-living entry — shortest, lightest, friendliest pin |
| 36RK | 40 ft | 4 | Rear-kitchen plan — the galley takes the back wall |
| 38RE | 43 ft | 4 | Rear-entertainment quad-slide — most-listed; 137-gal grey |
| 37MD | 43 ft | 8 | Middle-den quad-slide — two living zones |
| 39RK | 43 ft | 4 | Rear U-kitchen, bath-and-a-half — respec’d stretch; best margin |
| 39FL | 44 ft | 4 | Front-living flagship — five slides, heaviest pin |
| 40DB | 44 ft | 8 | Two bedrooms, two full baths — the multi-family flagship |
Every Bighorn is a 102-inch wide-body on the 12-inch I-beam drop frame, and the Premium Package is mandatory — its content (hydraulic auto-level, the GE residential appliance suite with inverter, central vacuum, gel-coat sidewalls) is part of the Base MSRP shown. This is a published-GVWR-clean line: dry plus cargo equals the printed GVWR exactly on all seven plans. RVUSA and the library brochure carry an early-print weight set superseded on five plans — the current factory pages and the June-2026 dealer-network brochure agree exactly and are used throughout (the 39RK was respecified from a 40-foot-4 two-slide draft to the current 43-foot-3 three-slide build, logged). Dealer placards typically run above Base MSRP while negotiated street pricing runs below it. A fifth wheel loads its pin into the truck bed — confirm the pin weight against the tow vehicle's payload placard, not its tow rating.
04 What owners & reviewers report
The den is the plan
A true second living zone amidships — door-separated space the bunk-room formula approximates but does not match for adults.
Eight berths, 2,450 pounds
The line’s top sleep rating against its second-tightest margin — load deliberately and scale the loaded coach.
40 feet of awning
Two 20-footers — the longest combined shade line in the roster.
05 How it compares
The other eight-sleeper — two true bedrooms and two full baths instead of the den, with a 100-gallon black tank.
The entry rear-living plan — 2,590 pounds lighter for couples who do not need the second zone.
The multi-zone luxury field — the 37MD counter is the standard residential suite and the zero-degree ThermaShield package.