Automatic Disconnecting Differential question

Is this an accurate description of what the ADD does?

"With an Add front end, your front driveline,diff, and axleshafts are always turning when the truck is moving. When you push your 4wd button the axle shafts extend (via a vaccum actuator) and connect to your cv shafts, putting you in 4x4."

I realized it's brief and incomplete, but does have the positive of short, sweet, and to the point.

Also, did all 1st gen 4WD Tundras have ADD and "live hubs?"

Thanks.

ps. Think maybe I found the answer here:

So, I apologize if this is redundantinformation- but it is very important to know.

There are two actuators that shift the truck into and out of 4WD. One of them is mounted to the transfer case, andthis one connects/disconnects the front driveshaft. The other one is mountedon the front differential, known as the Automatic Disconnecting Differential.ADD for short. This actuator connects/disconnects the front wheelsfrom the front diff.

When the truck is in 2WD, the front driveshaft should be free spinning, andthe front wheels should spin independently of each other.

When the truck is in 4WD, the front driveshaft should be locked and unableto spin, and the front wheels shouldboth turn when one is spun.

 

Start here:

https://www.tundras.com/threads/1st-gen-4wd-issues-diagnosis-prevention-guide.149189/

 

Your truck uses two electronic actuators. One on the transfer case, and another on the front differential. They are not vacuum actuated, though there are breather lines that go to both the ADD actuator and front differential which are commonly mistaken for vacuum lines.

The transfer case actuator disconnects the front driveshaft from the transfer case. In 2WD, the front driveshaft is disconnected from the transfer case, but is still connected to the front differential. Notably the pinion flange, drive pinion gear, and ring gear, and spider gears. The front driveshaft turns the pinion gear, which turns the ring gear. The ring gear transmits torque to the spider gears, which then turn the front wheels. The spider gears in your front differential are always turning, but in 2wd they are not receiving any torque from the driveshaft. Therefore, the front driveshaft doesn't really rotate in 2WD, and if it spins at all, it's due to the spider gears transmitting force to the drive pinion gear from the wheel rotation. If that happens, it would be spinning much slower than it would in 4WD.

The electronic actuator for the front differential is not on the differential/ clamshell, but on the A.D.D tube. When 4WD is engaged, there is a clutch inside the ADD tube that moves the ADD intermediate shaft (shaft #2) and locks it onto the differential intermediate shaft (shaft #1). When in 2WD, both CV axles are spinning, but only the driver's side is spinning the spider gears in side the differential. The passenger's side CV is only spinning the ADD intermediate shaft (shaft #2) since the clutch is disengaged.







This video does an excellent job breaking down the whole ADD process. This is on a newer Tundra, but operation is basically the same.

https://www.youtube.com/watch?v=47m7QAPrpsI&t=124s

 

Awesome info fellas. Much appreciated!

 

Agreed on the video. Excellent. I watched Weber videos on u joints awhile back. Top notch. Thanks for sharing!