I was a passenger in a vehicle that experienced brake failure on a long hill in Cameroon. The transmission was also in poor shape, the driver was able to hold the speed down to about 45 mph (the road was straight enough he could stay on it) but it was a very rough ride. We also ended up running a military guardpost at the bottom of the hill--fortunately they realized we were out of control rather than trying to crash the checkpoint. I saw their weapons--they had rifle grenades loaded.
(Turns out some bozo had assembled the brakes upside-down. They worked but the contact area was far too small and when we hit that hill they overheated.)