After 8 months travelling mostly offroad in northern/central WA outback, thought a few words on front diff lock might be useful.
1. fitted an ARB air locker to front only. Logic: this would be the best upgrade for a near new Troopy - ie rear LSD in new condition offers good performance at rear and gives LSD in 2WD
2. initial fitting failed - small compressor cycling every 15-20 secs indicated airleak. ARB fitted purge valve at no cost.
3. air filter unit fell off after 15,000km seemingly due to its having been cracked on fitting/assembly. ARB replaced under warranty
4. small compressor fitted too low in engine bay (low behind headlight) - causing me to switch on before entering deep
water and then switch off before reaching say 70cm - worried that the unit might pump
water into diff or be damaged.
5. used it all deep crossings, only the frightening
sand dunes, occasional bogs, and for extrication from deep washouts
Lessons
1. Check the cycling/performance before leaving the fitting
shop
2. have a say into where the unit is fitted - ie get it as high as possible or inside the cab
3. it gave no appreciable benefit in extrication from bogs and in sand (vehicle heavily laden)
4. seemed to provide value for clawing way out of short steep washouts (ie low range first gear lots of pedal)
5. consider carefully whether small compressor is the answer - if you have the room, opt for large compressor as this gives fall back for tyre pumping if your tyre pump fails (my ARB tyre pump has started making not funny noises)
6. maybe a rear air locker is on the cards
7. the switch lights for the airlocker are
bright whether the unit is on or off - have them mounted away from normal driving vision for night driving or get a dimmer.
Overall - not really the answer to lone vehicle travel in testing environment