Check your rental rate very carefully as it's common for a mileage charge to be added after the first 100km, which will not get you far in the Yukon. Also understand your insurance coverage and ask whether damage from Yukon's rugged roads is included.
Fraserway RV Rentals Rents all shapes and sizes of RV from $200 per day depending on size (it matters) and season. Mileage extra; rates can quickly add up.
Whitehorse Subaru Has good rates; most cars have manual transmissions.