I have a gap in the uptake of power during gear change after the mechanic removed the rear diff centre . He then realised it was my front diff to receive a locker. My rear diff never had this problem previously .I tightened up the unijoint bolts as I found them loose but still had the problem.No noise or vibration is present.

You will have to check the number of the teeth on the crown wheel and pinion gear as they have to match the old unit also the axle splines must be the same.

jack up the rear end high and place chassis rails on stands. Remove wheels . disconnect brake hose to the rear and use a hose pincher to stop brake fluid leaking out . Disconnect the hand brake cable at a convenient point ( probably at the rear of the transmission. Disconnect the drive shaft at the diff pinion and lay to one side . Place the jack under the diff housing centre and take a bit of weight. . If you have leaf springs --undo the "U" bolts around the housing . If coil springs undo the track rods by removing all the pivot bush bolts. Lower the diff housing down and pull out from under the car. Make any changes you have to, to the other diff housing before placing it on the jack and placing it under the car Reassembly is the reverse process of removal.. Bleed rear brakes on completion of the job.

all wheel drive vehicles have to work at both ends all the time unless you have a major failure in the drive train. That is why it is called all wheel drive as opposed to 4 wheel drive. With 4 wheel drive you have the option of rear wheel drive or 4 wheel drive and normally in a high ratio or low ratio gear selection. With some all wheel drive vehicles there is a selector that locks the middle diff and creates a 4 wheel drive option without the high/low gear ratio option. So in practice if the both front wheels are in the bog then there is no all wheel drive as the centre diff is working as it should and placing all the action in the rear wheels which will not be turning as they have traction so the front wheels spin faster.. If you have a centre diff lock option ensure that it is operational.

there has to be constant all wheel drive because that is the drive train design. A diff at the front --a diff in the middle (gearbox) and a rear diff. If there is no drive to the rear diff then maybe there is a problem in the centre diff and the previous owner removed the connecting drive bit .

Does it have manual locking front hubs? Some people fit these to full time four wheel drive vehicles to reduce driveline effort and increase fuel efficiency. The issue is that the drive from the transfer case will find the path of least resistance which if the front hubs are not locked power will be sent through the front diff and only spin the front drive shafts. To ensure drive power is sent to the rear diff the centre diff needs to be locked. If you do have manual locking front hubs try putting them in the locked position and leave the centre diff button off and try going for a drive.

remove the driveshaft then romove the yoke and the seal there may or may not be a clip holding in the bearing but when changing the bearing the race should be changed for this remove the wheels with the diff on stands remove the rear cover on the diff push the axles in and remove the c-clips from inside the diff then pull the axles out inside the diff you will see 4 bolts remove them and take out the spider gears and drive gear once the drive gear is out you can use a punch and hammer to remove the rase to insall the new rase use a BRASS punch as to not damage the new one then install parts as they came out

For the rear diff., remove the driveshaft, brake drums, diff. cover, remove pinion flange nut, move diff carrier to access side gear retainer bolt and remove bolt, slide side gear pin out and push axles in to remove axle retainers and remove axels. Mark carrier bearing retainers, spin bearing retainers to loosen carrier for removal. Remove carrier, remove pinion out of diff case, then r&r bearings. Any shims should be replaced in their original location for depth and pinion to ring contact.

jack car up and remove the rear shaft retainer plate, 6 14mm bolts. use a 12mm spanner to remove the 4 nuts and bolts on rear of tailshaft and front, take the shaft out completely, check for play in the front yolk of the diff, there should be very minimal play, if there is alot of play or worse your getting rotations then the front bearing is gone and will need replacing, you can get the whole diff centre fro about $260 from sunbury parts in qld. cheaper and quicker option, make sure the gear rations are the same.

Howdy, My name is Mark, I am a mechanic (Auto trans and Diff specialist 23 years) this symptom is common with a broken driveline component, with full time 4WD and centre diff all the drive goes to the wheel with least resistance, (or to broken component) therefore when you engage difflock (Center) the drive then goes 2 ways front and rear so vehicle will drive, could be as simple as stripped spline in front wheel hub, broken CV joint etc. 1 major weakness these vehicles have is if driven with center diff lock engaged on high traction surfaces they do break the front diff, this will give the same symptom but you would of been aware of it when it happened.
To check where the drive is going chock all 4 wheels, park brake on, bonnet up, start engine let it idle down (after cold start), engage reverse (high range open center) from the front of vehicle and off to one side you can see the front axles, if one of them is turning that is where your drive is going, have someone to help you and under no circumstances place your self under or in driving path of vehicle.
Hope this helps

yes you will have to change the computer. the rear diff wont have to be changed if the front diff has the same gear ratio.the entire front end suspension will need removed so tha you can mount the four wheel drive differential this most likely will require custom modifications. and the whole process will be very time consuming and expensive