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Front diff vacuum and breather hoses

Have a 2003 toyota tundra v6 manual sr5. Recently purchased. Trying to replace the front differential. The vacuum tubes and breather hoses have been previously cut. I cannot figure out where they should go to. I have the FSM. Cannot locate breather hose anywhere besides on the breakout diagram of front differential. Located vacuum hose running into front of engine but image does not match truck I have. Then I read somewhere that possible the hose for the add is not actually vacuum but just an additional breather? Where should these hoses run to? Looked all over the internet for info, cannot find anything that matches what I have. There is no vacuum cylinder in a wheel well as suggested all over the place. Any insight would be greatly appreciated.

The front diff has to have some sort of breather hose.

If it didn’t, as the gears/oil heated up the pressure would build to a point where it could blow the seals out.


Yes I know it has a breather hose, I can see the output from the diff. I don’t know where it should terminate.

The breather hose terminates above the diff so water can’t get in.

On the firewall is a good location to terminate the breather hose.


Thanks. And is the small hose coming off the a.d.d. actuator also a breather or a vacuum hose that needs to run somewhere else?

Is the a.d.d. actuator used for locking the front differential? As mentioned above the diff breather hose just has to be above whatever water level you expect to drive through. Usually it is tucked up inside the frame rails or similar.

Yes. There is electrical to it. It’s not push button, I have a second stick for it…

I don’t see any breather hose for the a.d.d. actuator itself. Like you say it has an electrical connection. But is there a corresponding actuator in the front differential ass’y ? I see something called the differential actuator that looks to be part of the differential ass’y. If so it might have a breather hose. There’s no diagram of the differential case breather hose either on the diagrams I’m looking at. I presume they figure a mechanic can sort that out without explanation.

There is a small hose coming off the back of the actuator. Unclear if it’s for a vacuum or a breather line. If it’s for vacuum I’m not sure where it is supposed to go…

A.D.D is Automatic Disconnecting Differential, the actuator engages the right axle shaft for 4WD operation, it is not for a locking differential.

The vacuum supply line for the A.D.D. actuator connects to a vacuum port on the front of the intake manifold plenum, below and to the left of the throttle body.

The differential breather is a vent, it only connects to the differential, the other end is left open and high enough to keep water out.

Some breather hoses go up and then down and just hang there. When they break off water will get into the housing. Check it now and then.