80 Series Transfer Case

[Citroënbender]

“On the tools” again to help a mate out.

A somewhat modded later 80 series has presented in 2WD only, with H/L sometimes difficult to engage or disengage. I’ve found the following web page a good start for information, but hoping a couple of dumb questions can be answered for me. Really need a repair or at least final diagnosis (from component testing) by Monday business hours.

Q1: Who actually makes the transfer case (ie, what brand)?
Q2: Are they shared with any other vehicles (for economical parts sourcing)?
Q3: Is Neutral (RWD) a deliberate position or incidental only?
Q4: Is the H/L range actuation wholly physically independent of the diff status?

Hoping it’s a simple fix. There are a number of aftermarket modifications of different ages; lift kit, onboard compressor and rear air locker, remote central locking/immobiliser, head unit, multiple extra lights and power outlets… I realise it’s possible one of these has compromised the power supply or wiring route. At least it’s analogue (electromechanical).