Question for M_Chan
Post Fiend
Joined: Oct 2009
Posts: 12,123
Likes: 35
From: N. Fort Worth, tx
So you dont recomend Lip Pressure LOL
mode
A high vacuum level (222 mm [8.75 in] Hg and greater) is
applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4x4 mode, and a lower vacuum
level (114 to 184 mm [5.9 to 7.1 in] Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD
applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4x4 mode, and a lower vacuum
level (114 to 184 mm [5.9 to 7.1 in] Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD
mode
Senior User
Joined: Apr 2012
Posts: 294
Likes: 0
From: Orlando, FL
I think what you want to do is pull vac on it and see if it will Hold Vac
Theres 2 Lines coming off the Vac Silinoid one goes to Climate Control other goes to 4x4
The Line going to the Hubs comes off the silinoid drops down about a Foot and then Splits into 2 for Each front Tire Put the vac test right there whatever one WONT Hold Vac is your Culprit then Chase the Bad side and Hook Into it Just Like Mike Mentions Right at the Hub see if the Hub Will Hold VAC
Hopefulley the Hub will Hold Vac and its Just a Bad VAC Line Cause them Hub Seals Can be Expensive and you will have to make the special Tool to Install it
There are Inner and Outer Hub Seals IDK if the Techs have a Way to Dial what seal it is Be IT a Inner or Outter Hub Seal or if they just Change All them
Is your Front end Leaf Spring Type or Coil over Axel???? the seals are diff I described Leaf style front end
Theres 2 Lines coming off the Vac Silinoid one goes to Climate Control other goes to 4x4
The Line going to the Hubs comes off the silinoid drops down about a Foot and then Splits into 2 for Each front Tire Put the vac test right there whatever one WONT Hold Vac is your Culprit then Chase the Bad side and Hook Into it Just Like Mike Mentions Right at the Hub see if the Hub Will Hold VAC
Hopefulley the Hub will Hold Vac and its Just a Bad VAC Line Cause them Hub Seals Can be Expensive and you will have to make the special Tool to Install it
There are Inner and Outer Hub Seals IDK if the Techs have a Way to Dial what seal it is Be IT a Inner or Outter Hub Seal or if they just Change All them
Is your Front end Leaf Spring Type or Coil over Axel???? the seals are diff I described Leaf style front end
My Front end is Leaf Spring Type. And what I think I will have to do is get a vacuum pump. I am pretty sure Mike was right in what the problem is since when I did my little test both engaged when I put it in 4x4. I just need to get a vacuum pump to prove it.
Senior User
Joined: Apr 2012
Posts: 294
Likes: 0
From: Orlando, FL
Probably cause when I was sucking on them with my lips they didn't 
.... However when I used the truck and put the switch in 4x4 they both engaged but A/C still went to defrost. I work with animatronics and it is probably leak by around the switching solenoid just enough to loose pressure and cause the duct to default.... atleast that is my guess I just need to buy the vacuum pump to test it make sure the leak by isn't in the hub or else where....
.... However when I used the truck and put the switch in 4x4 they both engaged but A/C still went to defrost. I work with animatronics and it is probably leak by around the switching solenoid just enough to loose pressure and cause the duct to default.... atleast that is my guess I just need to buy the vacuum pump to test it make sure the leak by isn't in the hub or else where....
Senior User
Joined: Apr 2012
Posts: 294
Likes: 0
From: Orlando, FL
If the statement highlighted in bold red is what your truck is doing, you likely need to have your PVH (Pulse Vacuum Hub) solenoid replaced. Simply pull the small section of vacuum hose connection of at the plastic junction before it enters the steering knuckle with the wheel lifted off the ground. Suck on the hose and see if it will build vacuum while spinning the wheel by hand at the same time to see if it engages the axle. If it builds vacuum and engages the axle, you've eliminated THAT as your source. Repeat the process for the other wheel.
Thanks Mike
Lead Driver
Joined: Mar 2010
Posts: 5,504
Likes: 256
From: Woodbridge, Ontario, CA
That is what I thought all along. Sometimes it takes seeing the positive result to make some people believers. On the same token, I'm glad your problem was fixed with such a seemingly simple to replace part.
Senior User
Joined: Apr 2012
Posts: 294
Likes: 0
From: Orlando, FL
I didn't doubt you. I wanted to go through the diagnostics to
1. Learn how to do it.
2. Learn how the truck works.
3. Confirm that was the broken part.
As has said many times we can throw money at a problem or get guages and/or troubleshoot the problem so we just replace the part needed. Since I am not rich.... and yes it was simple to replace. Thanks once again.
1. Learn how to do it.
2. Learn how the truck works.
3. Confirm that was the broken part.
As has said many times we can throw money at a problem or get guages and/or troubleshoot the problem so we just replace the part needed. Since I am not rich.... and yes it was simple to replace. Thanks once again.
Hotshot
Joined: Apr 2010
Posts: 19,055
Likes: 235
From: Saratoga Springs,UT
He means ME^^^^
and yes it was my BAD I will be the Bigger Man and admit I was WRONG
For some reason I thought the Hubs wouldnt engauge that whole time you was trouble shooting it
Just had in my mind wrong the chain of event and outcome
Thats Why MIKE does what he does he GOOD AT IT!!!!
So it must leak right right at the Silinoid??????
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Senior User
Joined: Apr 2012
Posts: 294
Likes: 0
From: Orlando, FL
while I am not familiar with this particular application I am quite familiar with air operated cylinders.... Normally there is a piston with a diaphram of some sort. When the solenoid fires it pulls (pushes) on the diaphram allowing air to flow around the diaphrom when the solenoid releases the system pressure reseats the diaphram and it stops. (The valves in lawn sprinklers work the same way except it is water). Eventually either the solenoid fail or junk gets caught in diaphram or the diaphram breaks down and you get leak by.
Another type would be just a solenoid with a piston. The solenoid fires the piston moves allowing air flow. There normally have some sort of spring assist to reseat the piston once the solenoid releases and O rings around the piston to prevent leaking. Either way they can be prone to internal leakage.
Another type would be just a solenoid with a piston. The solenoid fires the piston moves allowing air flow. There normally have some sort of spring assist to reseat the piston once the solenoid releases and O rings around the piston to prevent leaking. Either way they can be prone to internal leakage.
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