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2003 Chevrolet TrailBlazer -OK to disconnect 4x4 unit?

can I disconnect the 4x4 unit and have everything else work properly. I have an electrical gremlin in my Trailblazer, that randomly causes trouble. The dash selector,recently showed it was in 4low,and 2hi at the same time.

If a true 4WD, probably you could remove the front drive shaft. But before you do that, see if the gremlins can be found, might be a simple fix.

But if you don’t immediately correct the problem removing the front drive shaft could save you from some serious damage.

Changing the switch to auto does not change the lights?

Obviously the truck can’t be in 4 low and 2 high at the same time. Is it actually in 4wd? If it’s not you won’t hurt anything by continuing to drive it as is. Removing 4wd capability won’t solve your electrical gremlin. You need to sort that out.

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If it is a push button 4wd with low and all wheel drive… the switch is bad. Very common problem. $50 for a switch, 15 minutes to change it.

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it is a rotating knob, 2wd, auto, 2hi and 4lo are the selections. On mine there are led lights to indicate selection. There is an electronic module that is the control center, my guess is that is the problem. It is possible rotating the switch multiple times with the car off may help if it a switch problem.

I’m assuming this is true 4WD, configured with a transfer case that has its own differential, so it can be driven on hard surface roads in 4WD mode. If OP removes the front driveshaft, but the transfer case remains in 4WD mode, wouldn’t that result in a lot of wear to parts of the transfer case differential as the car was driven? Or if the x-case’s differential were the open type, the car might not even move. The front part would spin, and the rear drive part would do nothing. It would be sort of like removing one of the axle shafts in a rear wheel drive car. Unless a traction lock type, car ain’t moving.

The 4wd or auto activates the front drive shaft, but if you remove it you are going to have some major holes I think. I would think the easiest solution would be to disconnect the drive activation control plug on the transmission, but myself I would take it to a shop.

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“Holes.” I can’t imagine where @Barkydog. the drive shaft is connected to U-joints at each end.

There is a shaft to the front differential that goes through a pinion ring, Glad to be wrong, the original suggestion was to remove the front shaft.

The front driveshaft is a slip yoke connection to the transfer case, so if it were removed, there would be a hole around the output shaft and the t-case fluid would leak out.

The service manual has a diagnostic procedure for the symptom “Transfer Case Shift Control Switch Indicator Always On - Two or More”. It comes down to three possible causes:

  1. The mode switch is bad (maybe an internal short to ground for one of the lamps).
  2. There is a short to ground in the indicator lamp circuit ground wiring between the mode switch and the transfer case shift control module (the indicator lamps are controlled by the transfer case shift control module switching the lamp grounds).
  3. The transfer case shift control module is bad.

The transfer case shift control module can be accessed (it’s under the left side of the dash) through the dash side access panel and/or from underneath. Unplugging the black 16-way connector from it will allow testing of the indicator lamp ground wires from the switch. The wire colors are: 2hi-lt grn/blk; auto-pnk; 4hi-tan/blk; 4lo-ppl/wht; neutral-brn. Power to the switch for the indicators comes from the dash light circuit.

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These vintage TBs are known for this issue. If it was in 4Lo you’d know about it. The design is goofy in that logic state high = actice. So a failing switch or harness connection to the TCCM can result in weird or unintended states. Most often it just fails to work and throws codes related to 4wd. First thing is to be sure most recent code is flashed to controller. Then updated design switch installed- it has provisions to combat oxidation of contacts. That will probably fix it. There are two fuses associated with the 4WD system you could pull to deactivate it. One in underhood box, one in box under backseat. Forget exact ones but unless it is actually going into 4Lo mode (there are interlocks to prevent it from happening out of neutral or high rpms), I would just try the new switch first…

Please excuse my ignorance @jasonfarm. I seem blind in one eye while unable to see out of the other. A picture of a replacement drive shaft gave me no clue to the attachment.

That isn’t true 4WD… as argued by serious off-roaders. That is more accurately All-Wheel-Drive.

If the OP removes the front drive-shaft and the car won’t move… it is AWD with a diff in the transfer case. If it is 4WD, with no diff, all is well since the truck is now 2WD.

There are also actuators on the front axle that lock the hubs. Unplug each of the 2 actuators and the hubs will never lock. If the front driveshaft rotates, so will the front diff but that is as far as it goes.

There will always be people that attempt to argue minutia of details. Here’s my position- the big differences between 4wd and awd are two fold. Awd uses center differential and drives both axles from it whereas 4wd uses transfer case and front rear diffs. The awd can send variable torque to each axle but 4wd is fixed amount.

The trailblazer is part time 4wd by design. If you pull front axle it will still drive around.

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The transfer cases used in these TB’s are sort of a hybrid between 4WD and AWD. They don’t have a differential like AWD, but they do have a clutch system (kind of like limited-slip diffs) that can adjust the amount of torque going to the front axle depending on how much slip is detected at the rear.

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