[quote name='pete.young' post='1120698' date='Feb 8 2011, 09:55 PM']As far as the T4 synchro goes, it's a complicated system which will use more fuel than the 2wd system, but it's a lot newer than the type 25 so there are fewer aftermarket parts.
I gather that most are fitted with a rear difflock and they have a crawler gear in addition to the normal gear ratios but I can't confirm that.
I also hear that the front axles are liable to expensive problems which can be fixed by pulling the half-shafts: so if you do go and look at one make sure it's all intact![/quote]
Yeah the Syncros (not Synchro - common mistake ) are very complex, but off road they're miles better than a Defender, but more civilised on the road. And I don't get where you're coming from with the aftermarket parts, because the T25 / T3 Syncros were still done by VW, so it's not a fully aftermarket system.
As for the difflocks and crawlers, there's so many combinations it's hard to tell what is and isn't standard option, and there's also the Syncro 16 which is basically higher suspension and 16" wheels instead of 14" wheels.
Axle wise - yeah problems can occur if they've not been looked after properly and axles have been known to go missing, but that's common on a lot of viscous coupling 4wd systems. However yeah, make sure it's intact
There's always the option of the T5 4motion too Expensive though