4wd engagin on braking


I have a 2.8 Daihatsu Rugger (Rocky).
My problem, is that on braking, especially if i am going downhill or at a certain speed, the 4 wd automatically engages, ,and there is a "crackling noise". My mechanic tought it was something having to do with electric system. Took it to electrician, ,diconnected something from the gearbox....but to no avail. To get rid of the noise I have to slow down, press the clutch and brake, and it dis-engages. Any ideas what this might be, and how can I solve it...Thanks.

4wd engaging on braking

Do you have auto locking hubs? That would explain your crackling (ratcheting) which happens with autolocking hubs when they try and engage while moving.
All that tells you though is that 4WD is trying to engage, not why.

Given your mechanic tried disconnecting something from the gearbox - Maybe all he disconnected was the 4wd sensor or reporting light. You can lose this light and still get 4wd no problem. So I guess your problem is in te 4wd switching. I think it is vacuum engaged so its the control switch for this that may be your problem. I would look for stripped wires causing a short or earthing fault switching on the selector. I think yours might be a double positive wired car which means you break the electrical circuit to earth to switch on. If it is then this means both your feeds would be live normally. If you have an earthing fault on either one of your wires it will switch on. this would be the opposite of most cars where you would expect an earthing fault to cause a switch off.

Don't know if its right for your vehicle but it may help your mechanic elimanate a possible cause.