Welcome to Manins' truck camper project

Differential Locks

Using the Diff Locks

  • The centre Diff lock must be engaged before the rear diff lock will engage,
  • The front diff lock can not be engaged unless the rear diff lock is engaged.
  • The centre diff lock can not be engaged at speed, you must slow to below 40 kph before the computer will allow centre diff lock,
  • The centre diff lock automatically disengages over 80 kph
  • The rear diff lock will not engage above 20 kph, automatically disengages over 40 kph
  • The front diff lock will not engage above 15 kph, automatically disengages over 30 kph.
  • One beep when the lock engages, two when it disengages.

(ref. GoingBush)


TT30 middle dashboard with diff lock switches and ABS lights relocated to main switch bank, which includes overhead cabin light and spotlights switches. Empty bin at top for CB radio. Class 1 switches below. TPMS below those.

Check Light

The check light relates to the Hydraulic Fluid reservoir in the APU, also known as hydraulic diff lock pump, under the metal cover near the spare wheel.

  • Low or leaking hydraulic fluid, the light will flash (it can leak directly into the diff locks).
  • A steady light indicates a diff lock ECU failure.
  • Code flashing - 2 flashes alternated with 3 second pause - failure in the speed signal.
  • The self test protocol also illuminates the check light when the truck is started.

(ref. Marcus Tuck)

ABS Lights


OEM middle dashboard with diff lock switches and lights at the top.

The ABS is a Bosch 5.3 and is fairly basic. It doesn’t have any of the advanced stability controls, only 'anti-blocking'). ABS is automatically switched off when any diff lock is engaged.

The dashboard ABS light (in the speedometer dial) is not connected on the Daily 4×4 model; it is replaced by the big ABS light on the Differential lock panel. The little ABS light on the Differential Lock panel lights to tell us when the Differential Lock system has disabled the ABS. So if we have the Differential Lock off (i.e. the small ABS light off) and the big ABS light on, we probably have an ABS fault. If we have the Differential Lock on (i.e. the small ABS light on) and the big ABS light on, we do not have an ABS fault.
   (ref. Marcus Tuck)

Relocating Switches and Lights

All the diff lock switches and lights, including ABS lights, have been relocated to the main switch bank. The OEM cable and connectors are long enough. However the mounting frame in the vicinity of the main switch bank has to be cut away (two locating sockets and a cross member) and the little LED lights in their M8 x 0.75 threaded metal housings have to have their resistor and connector tubes cut so they can be bent to fit in the available space. Neutral-cure silicone sealant keeps them in place.


Middle dash frame. Below the switch sockets a cross member and location sockets have been cut away.


Rear view of modified middle dash panel. The LEDs require major changes to clear the frame.


Front view of modified lower middle dash panel. Diff lock switches are on the left, ABS and CHECK lights are on the right.

AFAM Computer Replacement

The AFAM is the computer controller for the differential locks. It also turns off the ABS when a lock is initiated (See also my changes to that here.). It is located under the driver's seat in a diecast box.

Marcus Tuck and Don Incoll have developed and sell a replacement for the AFAM Computer that obviates some issues with the AFAM and adds new features. See their discussions (here and here) for the problems with the OEM version and how the replacement computer works.

Note that the documentation of the hardware and software on the TucksTruck Web site has been superceded with numerous small changes, such as elimination of the signal photocouplers and the addition of the single-press Rear Diff Lock selector functionality.

A copy of the Operating Instructions (© Marcus Tuck) is available here.

Having installed a replacement AFAM I find diff lock selection much faster, though deselecting Centre Diff Lock can still take an unreasonably long time. A new feature is that a press of the Rear Diff Lock selector automatically initiates selection of first the Centre Diff Lock and then the Rear Diff Lock. Or, I can press Centre Diff Lock and then the Rear Diff Lock selectors without waiting for Centre Diff Lock to engage. Another feature is that ABS can be turned off by pressing the Front Diff Lock selector until the small ABS light illuminates. This is an alternative to using the ABS Defeat switch.



Removing the driver's seat makes access to the AFAM easy.


The new AFAM Computer is a drop-in replacement.


AFAM box lid back on, silicone bead seals the box. Double plug installed.