Probably not a good idea
I'd say getting to Nigeria will be fine... Morocco to Nigeria is almost all tar now.
However, from Cameroon until Namibia you'll have a LOT of problems trying to get an artic through. Here's an example: If you take the coast route from Nigeria into Cameroon (there are 2 border crossings, 1 in the north, 1 in the south near the coast) you will have to drive along what is often regarded as the worst road in Africa. It is known as the Mamfe road, it is 60kms long (from the border, to a town 60kms into Cameroon called Mamfe). In the rainy season that 60kms will take trucks and 4x4 / SUVs a week! There are sections of that road where the mud is so bad you can expect to do about 400m in a day!! There are potholes so deep that when we drove our truck into them, if you're standing on the side of the road you can't see the truck anymore! I hope I'm not freaking you out - I thought it was awesome, what an adventure like this is all about! I'm just trying to paint a picture that makes you realise the kind of conditions you'll encounter! It's by no means impossible, but it is very tough going.
I never once saw an artic on those roads. However, we often took the more off the beaten track routes. I think perhaps if you went on more conservative routes you may have a chance... although do keep in mind that Cameroon, Gabon, Congo and DRC are all predominantly equatorial jungle, with few or no tar sections. Getting an artic through thick mud... hmmm, I don't envy you! I'd say a rigid axle would be much more realistic, and a 4x4 even better.
All the local trucks I saw were rear-wheel drive, with double rear wheels. They often got stuck in the more tricky sections. As you know we had a 4x4 which just ate the mud. If you can, I'd suggest going for a 4x4 truck... if not, then a rigid axle with double rear wheels. I'd highly suggest not taking an artic. Best of all, buy mine!
Try speak to some of the overland companies - they may have more info on a feasible route. I know Dragoman does the west coast route... I'm sure there are others.
Hopefully some other people on here will have interesting things to say?
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