nuNce, DRG answered a post I had asking about exactly the same thing except it was completely different I was fighing too trying to get stuff loaded.

This is what DRG wrote:

IF a vehicle, any vehicle, can only carry infantry it will have a carry capacity listed something like
CARRY CAPACITY 13
IF a vehicle can carry gun of any kind it will be listed something like
CARRY CAPACITY 113
the 1xx indicates it can carry a gun but NOT a vehicle
Barges, gliders, barge carries can carry vehicles and are listed like this
CARRY CAPACITY 255
That means it can carry 55 total carry points ( 55 men ) or a tank with a carry cost of , for example 25 PLUS 20 men ( 25+20=55 ) or a tank that "weighs" 45 PLUS ten men ( again 55 total )
A 57 mm AT gun has a carry cost of 6 1 point for the gun PLUS 5 points for the 5 crewmen = 6 points and if needs to be loaded into a vehicle that shows 106 MINIMUM carry capacity ( 1 indicates it can carry a gun and 6 the maximum number of carry points.
This is what I came up with >>> So evidently NO tanks have a carrying capacity of 1 and then some more numbers. Evidently a tanks carrying capacity always reads 99 or less. This way they "can't" or "don't" carry anything requiring a 1 .. such as an anti tank gun...
I got this from the manual somewhere:
Lift capacity
Roughly, one man equals one lift point. However, some guns, mortar teams and so on cost more to lift (guns will have a '*' or '**' to indicate heavy weight). Vehicles with lift of 1XX can carry heavy units, 2XX really heavy units (look at say barges, which carry tanks etc.).
Load cost
This is the bit that says something is heavier than average, 0 for squads means only the men are factored, but say a .50 MMG section with Load cost of 1, will cost roughly 12 lift points, and tanks with load cost in the 24 ton class, need barges to carry. A 57mm AT gun with load Cost of 2 requires a vehicle with a 1XX Lift Capacity, and a 3 inch AT gun with Load Cost 3 needs a fair sized truck to tow it.