Chevy Avalanche Fan Club Forum

Avalanche Owners Zone => Chevrolet Avalanche Problems, Questions & Answers => Problems: Drivetrain & Steering => Topic started by: Jarhead1981 on June 13, 2018, 13:34:39 PM

Title: Need help on mystery hose!
Post by: Jarhead1981 on June 13, 2018, 13:34:39 PM
Hi,
   I pullled the motor and transmission in my wife's 2003 Avalanche 1500 Z71. 230K miles, tranny was getting weak so I figured I would do both. Left the Transfer case in, tail sitting on torsion bar key truss and front on a floor jack. Next day, I see that the jack leaked down causing the transfer case to sag and pull on the hoses and wires. When putting the new transmission and motor in I see a vent hose that goes through a bracket on the top of the transfer case but then goes nowhere and the end is open. The other end of the the hose goes up to the engine compartment and has the typical vent end on it. I used a drop light and a mirror to look for a vent pipe needing a hose and was unsuccessful. I did see the Transfer Case vent line coming out of the case via a plastic elbow and it travels to the transmission where joins via a "y" with the transmission vent and travels to the engine compartment. I know there has to be something, somewhere that this hose connects to. Does anyone have an idea? As I was typing this, I started wondering about the gas tank since it is located so close. Could that be a possibility? Any advice would be certainly welcome.
As an aside, I'm a partially disable Marine, 25 surgeries to date, and spending extended lengths under the truck looking up and around is killing me. I'm not asking for sympathy, I'm a Marine, I'm just looking for the most direct route to the fight.
   I did seek advice from our local Swansboro, NC Chevy dealer and the attitude of the service manager has convinced me to never do business with them.
Thanks, in advance.  Bob
Title: Re: Need help on mystery hose!
Post by: JVZL1 on June 13, 2018, 16:45:06 PM
  I believe it's for the front diff is what you are looking at. I can't remember where it
comes out on the diff.
Title: Re: Need help on mystery hose!
Post by: Jarhead1981 on June 13, 2018, 18:02:44 PM
Thanks for the reply but it's definitely not for the front differential. The vent capped end starts in the engine compartment near the dipsticks and travels down the passenger side of the transmission, across the top of the transfer case, thru a bracket on the top of the transfer case and several inches later, the open end is there. To reach the front diff, it would need to be 5 or 6  feet longer and go right back to the front.
Title: Re: Need help on mystery hose!
Post by: MS03 2500 on June 13, 2018, 21:40:03 PM
First and foremost THANK YOU for your service.  :thumbsup:

Now if it's attached to the Transfer Case and the Transmission then to the Vent cap I'm not sure what you are asking.
Title: Re: Need help on mystery hose!
Post by: Jarhead1981 on June 14, 2018, 02:34:03 AM
There are 3 hoses involved. 1 hose comes off the Transfer Case vent elbow and travels forward to the transmission where, by way of a "y" coupler, it connects to the transmission vent and hose 2. Hose 2 then continues on to the engine compartment. I don't have any questions about these 2 hoses. Hose 3, runs next to the previous #1 and #2, travels alongside the transmission, THRU a loop bracket on the top of the transfer case and extends about another foot. It is not connected at either end. It's ONLY connection to the transfer case is that it travels thru a bracket mounted on the top of the transfer case.
Title: Re: Need help on mystery hose!
Post by: ygmn on June 14, 2018, 04:24:48 AM
I think it just hangs to vent tranny and xfer case.
Heck I do not think it goes that far either...
Some older threads on here where people have questions about tranny VENT HOSE and they have pictures.

But I think I remember the vent hose just ending near bellhousing top so it is above tranny and tranny cooler lines.

might be worth a search in this section for "VENT" or "VENT HOSE"
Title: Re: Need help on mystery hose!
Post by: ygmn on June 14, 2018, 04:38:14 AM
some I found that may help:
http://www.chevyavalanchefanclub.com/cafcna/index.php?topic=149159.msg2130042#msg2130042
http://www.chevyavalanchefanclub.com/cafcna/index.php?topic=142180.msg2057815#msg2057815

How to R&R Transfer case:
http://www.chevyavalanchefanclub.com/cafcna/index.php?topic=120623.0

http://www.chevyavalanchefanclub.com/cafcna/index.php?topic=115424.msg1796433#msg1796433

There are many more but I hope this gives you an idea.
Title: Re: Need help on mystery hose!
Post by: Jarhead1981 on June 14, 2018, 14:16:57 PM
It's not connected at either end, so how could it be a vent for anything?
Title: Re: Need help on mystery hose!
Post by: carnut on June 14, 2018, 18:05:34 PM
If you look at step 6, it shows where the vent hose attaches to the transfer case. VERY hard to see with the transfer case installed.

http://www.chevyavalanchefanclub.com/cafcna/index.php?topic=120623.0

So, you have hose "A" connected to the transfer case vent port. The other end of "A" connects to the "Y" coupling above the transmission at the bellhousing area.
One side of Hose "B" connects to "Y", and the other side of "B" terminates at the transmission vent port on top of the transmission.
Hose "C" connects to the last "Y" port, and travels along the bellhousing and ends near the transmission dipstick in the engine compartment. The open end of "C" has a plastic vent cap to allow the system to "breath" without getting dirt in the system.

Hope this helps. If you have a left over hose, then I am clueless. Good Luck.
Title: Re: Need help on mystery hose!
Post by: carnut on June 14, 2018, 18:49:50 PM
I found this too while searching for a diagram. Does this match closer to what you have?\

http://www.gmfullsize.com/threads/what-is-this-hose-for.300554/

You can actually see two different vent hose circuits in the diagram. The second circuit is not labeled.

here's a better diagram:
Title: Re: Need help on mystery hose!
Post by: Jarhead1981 on June 17, 2018, 17:34:23 PM
Carnut,
   Thanks for your reply and most importantly thank you for the diagram. Though the diagram is reversed(my front drive shaft is on the other side, the concept is identical.  Most importantly, I want to address some posters who provide answers that are incorrect, as it seems that some of them provide answers simply to "post answers" and "rack up points" toward another badge.
   To others that experienced this problem with the vent hoses. There is "NO HOSE THAT RUNS FROM NOWHERE TO NOWHERE", every hose in there was put there for a purpose. Secondly, and more importantly, The Transmission and the Transfer case DO NOT SHARE A COMMON VENT." and there is a easily explained reason why some think so.  The transfer case vent IS NOT on the same vent line as the transmission. The Transfer Case vent runs from the Transfer Case to the engine compartment, and no others on it. The confusion arises in that the Transmission Vent originates in the engine compartment, and runs to the "Y" connector where it ties win with the Transmission vent tube on the topside of the Transmission. From there, it travels down to where the shift linkage is located and is left open and clipped there. Why? The transmission then has a vent for pressure changes but it also has an outlet for boiling transmission oil in the event that the transmission is over-worked/over-heated and the hose provide a method by which that oil can leave the transmission without possibility of spraying onto the radically hot CATALYTIC CONVERTERS, thus causing a fire. The open end of the transmission vent hose is secured with a clip in the area  of the transmission linkage.
   In no case would GM route a hose from the passenger side engine compartment to the transfer case only to run back to the front "diff". This is one of those answers that I previously addressed. Intelligently reading a post will save an individual a lifetime of embarrassment for their "answer" in the same way that intelligently presenting battlefield evidence will provide the greatest path of success and least  number of casualties. Bottom line, if you don't know, then you shouldn't say anything. If you after the "answer points", just say "I don't know"
   Carnut, thanks again for an answer that shows that you read and understood my question and posted an answer that is more relevant than the cost of beer in Bumfuc Nowhere.

Bob