What engine, tranny, T-case and axle ratio does that thing have? Any lockers in the axles?
Since there's only 15 posts in this subforum, I don't feel bad about dragging this one back up to the top, as I just picked up a C-304 like his last year I can provide some answers for you.
Engine is a Volvo B30A 3.0 liter inline 6 cylinder Gasoline engine, originally designed to run leaded fuel but can be converted to unleaded.
Transmission is a 4 speed ZF, Transfer case is also a ZF I believe, custom for the Volvo (input/output sides are reversed from most transfer cases). Axle ratio for the C-304 series is typically 7.1:1, (C303's get a 5.something:1, and the C-306 series get a 7.5 I recall - except for the fire truck versions which get the C303's 5.something ratios for speed.)
Some of the C306's also were paired with a 5 speed transmission, however the C303 and 304 series wheelbase (between front and mid axle) is too short to allow for the longer 5 speed transmission. The drivetrain package is REALLY tightly packed in there, which is annoying when considering trying to do any drivetrain swaps or addition of an overdrive. The 4 speed gearbox leaves it geared a bit low for highway driving, but with larger tires it's doable, but you lose a lot going up hills and the larger wheels do stress the drivetrain a bit.
All axles are equipped with vacuum operated locking differentials.
The vacuum system of the differentials is such that vacuum is required to unlock them, if the vacuum lines fail, the differentials will lock - this is to allow maximum traction in case of damage, to prevent a loss of mobility.
All of the C3 series vehicles have shift-on-the-fly front axle drive (4x4 for the 303, 6x6 for the 304 and 306, there is also a commercial varient of the 304 that has the same frame length but is only 4x4), and a brake switch attached to the front axle engagement mechanism - if you hit the brakes hard enough, it will automatically engage the front axle to assist with emergency braking.
The cab-forward design is interesting, the only real complaint I have is noise from the mechanical fan that is attached to the engine by means of a very long slender driveshaft with a couple of universal joints along the way. There is no fan clutch, the fan is directly tied to engine RPM's, so when you rev up, that fan makes an unholy racket and whine.
I'm looking at replacing mine with an electrical fan this summer, I've heard that really helps with the noise.
It's really quite the unique vehicle, I'm currently at work but I'll post a lot of photos of mine in a new thread when I get home.