New 80 owner with front diff issues

Jul 23, 2022
Hi everyone, I’ve recently bought a 1994 80 Series 4.2 HDT 12V.
It’s a great car and I’m really happy with it, just having a few issues with it and have been reading up on them but still scratching my head a bit.

To start off it needs the inner axle bearings and knuckle rebuild as there’s oil on them, the front diff was a bit whiny over about 40 so I changed the oil and it was black, so I’m sourcing a new front diff to put in while the half shafts etc are out anyway.

Here’s where it got a bit complicated, from what I’ve read to remove the front diff, it needs to be locked or it won’t come out?.
All 3 lockers were working fine on my test drive but when I tried to get them to work again they wouldn’t.
The CDL would not engage when I put the car in low, so I read up some more and identified the sensor or the actuator being the possible causes, put a new sensor in and no luck so used the paper clip method on the plug and voila!, CDL and ABS light illuminated although the CDL was unlikely locked, tried the front and rear lockers and they just flashed as usual and nothing, when moving the car again later the front diff lock engaged even though the switch wasn’t on!, now it’s stuck on and I’ve no idea how to get it to switch off.
Again thanks to this very useful forum we tried the 9V battery method and nothing and couldn’t get the cover off because one of the bolts was rounded off and it was getting late, front diff needs replacing anyway and is now locked, if the new diff gets put in, in the locked position too, should it be possible to disengage it?.
It unfortunately needed driving on a paved road for about 1.5 miles which was very difficult, the rear and centre locker weren’t engaged but the front was, I drove very slowly at about 20 mph and turned as lightly as possible, I even reversed to get the line right when I had to make a turn as fortunately the roads were quiet and I was able to.

I guess what I’m asking is, is there any other way to disengage the front locker?, is the actuator hard to get working again?.
Could the diff being worn from CV grease getting contaminated with the diff oil mess up the actuator and cause it to stick?, or is it sounding more like another electrical issue?.

I’m new to these trucks so any help and advice would be much appreciated, my main concern isn’t saving the diff that’s in it now but being able to get the new diff I put in to unlock once my axle bearing and diff swap are done.

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