keikosman

Thanks Jbrew.

What does the front axle breather do?

Jbrew

Helps keep the gear lube from over heating and breaking down. The rear axle has one as well.

ibd2328

iTrader: (2)

https://f150diy.com/files-pdf-1

keikosman

Awesome source! Thanks!

Jbrew

That would make for an excellent sticky.

Booked !

keikosman

Google search confirmed that it is the 4x4 Front Axle Vacuum Lower Tube Part number XL3Z3A785AA.

jethat

The 4x4 vacuum lines on my 99 definitely route that way. I have 2 actuators mounted next to the starter relay if I recall correctly. Not positive that's from those but it might be.

jethat

Ive repaired breaks in mine with a really small piece of vacuum hose and its lasted for years.

keikosman

So, I replaced the 4x4 Front Axle Vacuum Lower Tube last January and didn't have the opportunity to test it out much since then.

I recently tried to toggle between 4wd and 2wd and heard a ghastly noise. I finally found a site that shows how to diagnose 4WD problems . This guy must have saved me over $1K in truck repairs just in the last year.

I discovered that the feeder tube for the 4WD solenoid had a hole. Grabbed a good replacement from the local scrap yard and while installing it, I discovered the replacement vacuum lower tube assembly had a problem. The blue tube of the replacement lined-up with the pink tube of the original vacuum upper tube assembly. When I plugged it in as-is, the 4WD actuator would lock the hubs when the switch was on 2H and unlock when in 4H. I had to switch the blue and pink tubes on the lower tube assembly's triangle connector and completed the rest of the diagnosis to demonstrate it was working.