Outer Limits 4x4 Board

Ok .. have done a search & gone through countless posts..
I have a 98 Ti wagon with the factory diff lock in the read.. Never had any problems UNTIL sat nite

Anyone have any suggestions as to why it's not working ... was at the start of the trip then 1/2 way through .. wasnt.

Is there any common problems?

Any help would be appreciated!!!!

Check the fuse,
Check the wiring under the car to the switch on the diff- may be locking but light not working,
Check the vacuum lines to the diff,
Test the on/off solinoids on the firewall are operating when you turn the switch on and off.
Check the vacuum lines everywhere,

Thats all I can think of right now.

assuming its the same as a GQ
No vacuum to rear, check solenoids for power and passing vacuum, mounted l/h top firewall
Vacuum at rear, diapham unit damaged or diapham failed
Vacuum at rear, diapham holding vacuum, diff lock has been engaged whist wheel spinning causing damage to dog clutch: fit ARB unit and shorten r/r axle
J Top