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2002 chevy trailblazer_ls
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Discussion Starter · #1 ·
My 2002 TB 4x4 selector switch light is switching from 2HI which is normally what its on and switched to 4HI on its own. Usually happens when Im on highway I ten put it in nuetral switch it back to 2HI and OK.
Recently the wife pulled out of a praking lot and it switched to 4lo and
slowed down instead of accelerating ...barely moved. Then it wudnt go in reverse, so I put it in N switched it to AWD then back to 2HI and I heard clunck" sound and OK..cud this be the transfer case selector switch under dash I've heard about?
If so, how do I get to it to change ? Thanks!
 

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2004 gmc
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What you're describing sounds like a switch problem only. If you don't exercise the switch and 4WD system every month or so, the switch contacts can oxidize, and the electric actuators can freeze up. The 4WD system is my specialty.

Because of the switch design, a high contact resistance can be misinterpreted as a command to go to 4HI or 4LO. It would have been so easy for the designers to have this go the OTHER way for safety, but they didn't think of the problem of aging switches.

The clunk sound is normal, and comes from the transfer case.

As a first experiment, with the ignition off, just run the switch from end to end 40-50 times. That may clean off the contacts. Then run the vehicle through all the 4WD modes as a test. Do this every month from now on, to keep it ready.

If that doesn't solve the problem, then just buy a new switch from a dealer or Ebay. The good news is there's a lockout, so it can never accidentally go into 4LO while you're in gear or rolling more than 5 MPH. You have to be in neutral and under 5 MPH to go into or out of LO range.
 

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Discussion Starter · #3 ·
Thanks for your advise..I'll try it from now on and see if I still get it. just for my info, where is the switch exactly on the TB?
 

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The selector switch is the knob on the dash where the mode lights are.



I see you asked about the "transfer case selector switch" in your first post. That's not under the dash. What's under the dash is the TCCM (transfer case control module) above the driver's left knee. That's where the electronic magic happens. There is also a front axle actuator on the passenger side of the oil pan that engages the front differential, and an encoder motor on the side of the transfer case that accomplishes the real work of moving the transfer case gears and clutches for the various modes.

Now you have the nomenclature. :D
 

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Discussion Starter · #5 ·
AHHHH Gotcha Sorry thought there was a switch somewhere under dash...!!
Thanks Rodie!:duh:
 
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