Thor Aria 3901 vs Tiffin Allegro Bus 40IP

Thor · Class A

The difference that matters

Two diesel pushers of about 40 to 41 ft, separated mainly by size of chassis. The Allegro Bus 40IP rides Tiffin's PowerGlide XC raised-rail chassis with a 450 hp Cummins L9 and a 42,000 lb GVWR. The Aria 3901 uses a Freightliner XCR with a 360 hp Cummins 6.7 L and a 35,320 lb GVWR, with a 10,000 lb tow rating.

Power is the next gap. The Tiffin has a 10.0 kW Onan diesel, three 200 W solar panels, a 3,000 W inverter and six 6 V AGM batteries, with lithium optional. The Thor has an 8.0 kW diesel with auto start, 100 W of solar, a 2,000 W inverter and four 6 V batteries. It also has an AquaHot 250D hydronic system, an induction cooktop, a third ducted A/C and automatic leveling.

The Thor sleeps six, has a dual-vanity ensuite and stands 12.5 ft tall against 13.3 ft. The Tiffin sleeps four, has four slides and larger tanks, 96/91/53 gal against 91/51/51.

Thor Aria 3901: Diesel-pusher buyers hosting guests as a couple, wanting hydronic heat, induction cooking and a lower roofline.
Tiffin Allegro Bus 40IP: Full-timers who dry camp and want more solar, a bigger generator, four slides and a stronger engine.

Weights

2027 maker figures

GVWR: 35,320 lb
Dry weight (UVW): not published
Occupant + cargo (OCCC): not published
Towing capacity: 10,000 lb

Weights

2027 maker figures

GVWR: 42,000 lb
Dry weight (UVW): not published
Occupant + cargo (OCCC): not published
Towing capacity: not published

Spec for spec

	Thor Aria 3901	Tiffin Allegro Bus 40IP
GVWR	35,320 lb	42,000 lb
Towing capacity	10,000 lb	—
Exterior length	39.9 ft	41 ft
Exterior height	12.5 ft	13.3 ft
Sleeps	6	4
Slide-outs	—	4
Fresh water	91 gal	96 gal
Gray water	51 gal	91 gal
Black water	51 gal	53 gal
Factory solar	100 W	600 W
House battery	Four (4) 6-volt Auxiliary House Batteries	(6) 6V 300Ah extended-cycle AGM (lithium optional)
Generator	50 State 8.0 kW Diesel Generator	10.0 kW Onan Quiet Diesel
Chassis	Freightliner XCR	Tiffin PowerGlide XC raised-rail rear-engine diesel
Engine	Cummins® ISB-XT 6.7L (360 HP & 800 lb-ft Torque)	Cummins L9 450 HP (X15 605 HP optional on longer plans)
Fuel	Diesel	Diesel

Bold is the lighter or larger figure. A dash means the maker does not publish it.

To scale

051015202530354045 ft

Thor Aria 3901 · 39.9 ft long · 12′6″ tall
Tiffin Allegro Bus 40IP · 41 ft long · 13′4″ tall

Drawn to one scale from each camper's listed length and, where the maker publishes it, its exterior height. Outlines are typical for the camper type, not traced from this model. The figure is a 6 ft person. The dashed blue line is 25 ft, the length about 93% of national park campgrounds accept.

Thor Aria 3901

Full spec sheet, sources →

Tiffin Allegro Bus 40IP

Full spec sheet, sources →