How Does 4x4 System Work?
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Senior User
Joined: Feb 2004
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From: Austin, Texas
How Does 4x4 System Work?
Does anyone here have first-hand knowledge of how the 4x4 system on these modern trucks works? Specifically, I want to know how the dash-mounted 4x4 switch actually engages the transfer case (solenoid? electrical or vacuum?) and how (or if) the front hubs are locked/unlocked. On my previous generation 4x4 vehicles, I had a lever to engage the transfer case and either manual or automatic locking front hubs. It seems to me that if there are no traditional hubs that the front axles and related drivetrain would spin unnecessarily. Someone please enlighten me.
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Joined: Aug 2004
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I am not sure about transfer case operation. However on 04 - up trucks the hubs are vacume operated. Apparently the default setting is hubs locked. This week when I changed out my shocks to bilsteins I noticed this. I had the front end up in the air and was changing out my shocks, just for fun I grabbed the cv shaft, to my suprise it was engaged to the front differential. I tried the other side and it was engaged also. At first I thought the hubs were non functional. So I started the truck and rechecked both cv shafts, they both spun freely. That is when I realized when your truck is off or in 4 wd the hubs are locked when started and in 2 wd the hubs unlock. This is a nice redundancy feature so if you have a vacume leak you still have 4 wd, but also your cv shafts are spinning all the time.
Senior User
Joined: Mar 2005
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D-Hawk,
I was getting an oil change and with the truck in the air I spun the front wheel. I was surprised when the tire did not move easy and the other tire spun backwards. It was clear the hubs were engaged. I immediately went and found a service tech that could explain why this happened. He explained that in fact it was vacume and that the default was engaged. His reason was that if something broke when 4 wheeling, you would still deliver power to the wheels.
I was getting an oil change and with the truck in the air I spun the front wheel. I was surprised when the tire did not move easy and the other tire spun backwards. It was clear the hubs were engaged. I immediately went and found a service tech that could explain why this happened. He explained that in fact it was vacume and that the default was engaged. His reason was that if something broke when 4 wheeling, you would still deliver power to the wheels.
