Thread: Vacuum activated centre diff lock

I'm not sure what vehicle and transmission you have, but I have successfully removed and replaced the actuator in situ on a County with an LT95. From memory, when the pin is pulled out, the diff lock actuates.

Originally Posted by Mustlust

Diff locked in and seems vacuum actuator is stuffed. Previous owner would never have used the diff lock and I'm guessing vac diaphragm has perished. I plan to get a replacement from the UK, but in the interim would like to disengage the lock.
How can I do this? Can I remove the vac unit and pull the diff lock? Won't be needing the diff lock soon so can live without it for a bit. Probably not a good thing driving around town with diff locked in.

Are you sure it's the actuator, I see in a separate thread of yours that you have vacuum line questions. So if you have a vacuum leak somewhere or the vacuum switch in the cabin is faulty that will stop it working. Work out where the problem is first and then go about replacement from there. Take out the centre console and the panel underneath so you can get access to the rear of the vacuum switch (just above the transmission tunnel) With the engine running, pull off the middle hose that comes from the engine and put your finger over the end of it. There should be vacuum there. If none, check back along the line for leaks, if there is put it back on and pull the 2 hoses off the vacuum actuator. If the switch is in (off position) there should be vacuum at the rear hose, and at the front one if the switch is in the on position. You should be able to work out where the problem is from checking this. If you can get vacuum on both lines and it is not unlocking it is most likely that the vac unit diaphragm is stuffed. If there is vacuum to the switch and none at the 2 lines that go to the actuator, the switch is faulty. To unlock it you either have to unbolt the unit from the side of the transfer (drain the transfer case oil first) and manually unlock the dog and then you pull the fork back on the unit and bolt it back on until you can replace it. Another way is to drill a 1/2 inch hole into the side of the front part of the vacuum unit and insert a screwdriver to move the piston back towards the rear and disengage it. If there is oil in there it usually means the o ring that seals the piston shaft is u/s and that is probably what caused the failure of the diaphragm. You will then have to seal the hole before you refill the oil. Definitely not a good idea driving it around town in the locked position - you are going to get a lot of transmission wind up and stress on driveline components. Happy hunting