16 inch 1.6td syncro problems. Had it a few years now, got it from Mr Plompen and has always had CJ of syncrospares keeping it sweet. It has developed over the last few months (only enough to convince me it was real in the last week) a problem (more than the few that it has that can be ignored) . After about 45 mins it starts to feel it is heading into a headwind or it is pulling a trailer. the engine seems to have the same amount of (feeble) power but it feels it is pulling against something. Its losing 10 mph top speed and a good deal of acceleration, Hubs are not hot so don't think its brake related, no sense restriction at walking speed, no more bumps, knocks or noises than normal. No smoke or any more loss of oil than is usual. If you wait 20 mins it is ok for about 20 mins then it starts again. Its getting worse, round trip oop north (700+miles) with family and all the crap that has to be loaded too saw to that. Going to check all tyre pressures, full oil and filter change and check diff/ gearbox levels (any hints on levels and type of oil for diffs / gearbox? ) put oil treatment in and injector cleaner in it for a starter for ten, but any wiser heads out there encountered this before ? P.s it has a decoupler on it to avoid this sort of thing so not sure its a 4wd type problem. Otherwise its the long haul to the new syncrospares.
Andy the fat surfer.
UPDATE.
Air filter "diabolical" which I think means quite blocked, and both diffs empty

p.s tried to find gearbox code but came up with SOP or SDP which checking the list does not exist, so thats not it. Any clues as to where the number will be? make it simple, as if it is not obvious by now, I am a a f#%kwit