1992 Chevrolet Trailblazer



January, 21, 2006 AT 8:24 PM

When I want to engage 4 wheel drive high, it don't work. But if I engage 4 wheel Low and then go from low to high. Its makes a VERY LOUD grinding noise when I shift from either Reverse or Forward, WITHOUT even hitting the gas pedal?

Its so loud it makes you think your going to blow the transmission!

But if you put it back in Neutral and push the 4wd high enough times it will eventually kick out of doing this!

Plus also the 4wd low works strange sometimes too SOMETIME even when you push the button for 4 wheel LOW it makes BOTH 4 wheel high and low lights come on!

The actual dash mounted switch works fine because we took it out and used a ohm-meter to test it and it works great!

We have also tried replacing the 4 wheel drive control module located on the main computer for the vehicle!

I HOPE to suspect this may be a transfer motor problem, and I am HOPING it has nothing to do with the wiring!

If I short the diagnostic terminals, the 4wd switch indicates its a number 2 (encoder circuit fault).

ANY ideas on how to fix this is GREATLY APPRECIATED! THANKS!




2 Answers



January, 27, 2006 AT 1:04 PM

I also have a similar problem and have been looking for a solution. I have a 1994 GMC Jimmy with Electronic Transfer case. I have replaced the module under dash and still same problem. I can get the unit to shift into 4-wheel drive as described by the owners manual as the back up method.

Place vehicle in neutral, moving 1-2 mph, then shift into 4LO then as the lights are blinking place in Park. You can shift into 4HI or 2HI using this method. But it will not shift into 4HI on the fly.

The manual says that the " transmission contol switch" needs adjusted. I have looked in the Chiltons and online and cannot find this switch. Hope this helps you and someone else can help me identify this switch location and how to adjust it.



January, 27, 2006 AT 6:10 PM

The problem is that the 4wd has NOTHING to do with the transmission. The only major part to the 4wd is the Transfer case!

I have looked for that switch you mention in a transmission book and its not listed. So it sounds like where you got your information from isn't reliable!

I have talked to my local dealer and there transmission expert thinks the main problem is either the 4wd engagement motor and/or the whole transfer case.

The 4wd drive motor is loacted RIGHT on the transfer case! Its main job is when you push the 4wd drive switch its to turn a shift in the transfer case to " lock in" 4wd!

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