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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Rear Drivelines, Drive Axles and Gearing => Topic started by: philo_beddoe on April 13, 2017, 09:53:51 AM

Title: What is this and its function?
Post by: philo_beddoe on April 13, 2017, 09:53:51 AM
I dont have a pic yet, but its a black hose coming from top of rear diff and attached to bottom of bed. It has a plastic button type thing that pushes in and out.
Title: Re: What is this and its function?
Post by: csdineley on April 13, 2017, 09:55:39 AM
Vent tube.
Title: Re: What is this and its function?
Post by: VileZambonie on April 13, 2017, 12:48:34 PM
It's a breather connected to the vent hose.
Title: Re: What is this and its function?
Post by: philo_beddoe on April 13, 2017, 02:09:58 PM
Does air go both ways or just vent out?
Title: Re: What is this and its function?
Post by: GMCMedic on April 13, 2017, 06:43:46 PM
What they said

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Title: Re: What is this and its function?
Post by: philo_beddoe on April 13, 2017, 10:25:02 PM
Got it...."vent"
Title: Re: What is this and its function?
Post by: VileZambonie on April 14, 2017, 07:29:56 AM
It's designed to allow venting as the axle and lube heats up. As it cools, a negative pressure closes the valve. For normal use they are fine but can fail which typically leads to failed axle seals, pinion seals, water intrusion etc. Some people prefer to run a small filter vent with no valve and a relocated hose if they do off-roading or mud bogs. Unless you are seeing leaks and water intrusion, just leave it be.
Title: Re: What is this and its function?
Post by: philo_beddoe on April 14, 2017, 10:32:01 PM
No leaks or water, it was grimy, so i just cleaned it up.