I have 4wd again! As I mentioned in an earlier post, the Automatic Axle Disconnect (ADD) on the T100 was randomly disengaging while in 4wd. The ADD works by using solid hubs to connect the wheels to the front axles. The passenger side axle is permanently fixed to the differential, but the driver’s side goes through a vacuum actuated disconnect before it reaches it. Since the front diff is open, with even one side disconnected the front driveshaft is prevented from spinning. It’s reasonably robust, but the downside is if any part of the vacuum actuator system fails you’re stuck without 4wd. You also can’t use an auto-locker in the front since the passenger side is always turning. I decided to do away with the ADD system entirely by fixing the disconnect in the on position. This is relatively easily accomplished by removing the disconnect from the diff, sliding it left, and holding the arm in place with a hose clamp.

Hose clamp in place

That leaves the front axles permanently locked to the front diff. To prevent the front axles and driveshaft from spinning while in 2wd I ordered rebuilt manual locking hubs from Wabfab last June. It took until November for the hubs to arrive, though at least the quality of the rebuild was decent. They’re from an older Toyota pickup and bolt on in place of the solid hubs.

Before and After

I’ve had to use the 4wd several times since and it’s worked flawlessly. Locking the hubs in a snow storm is less than fun, but it’s been worth it for the peace of mind in knowing it will actually engage.