I have a 2000 s10 blazer with a vibration under the vehicle ... took it to a repair shop and they wanted 700.00 dollars to fix it , said it was the drive shaft between the transfer case and the front axle that was not dis-engaging from the transfer case and said it was the transfer case control module that was bad.Has anybodu else had this problem ? and what did you do? Also can a used one be used or new? and do they have to be programmed?

Thanks in advance.

 

Put the vehicle in neutral with the parking brake on... now crawl under there and grab each driveshaft and check out those u-joints. Even if the front shaft is always spinning, it still should not vibrate.

 

Well actually he would be getting some vibration because 4x4 engaged is a bad thing at greater speeds, so there for you will get vibration

 

Very similar to what I just went through. I fixed mine DIYS for about 50.00 (tranfer case vacuum swith and front differential sensor switch). If 2WD is selected the front drive shaft should not turn, you can have someone move the Blazer while you look at the drive shaft (or jack front left wheel and spin it, drive shaft should not be turning in 2WD.
If it is turning, here are a few things you can try to confirm and diagnose the problem:

1. When you press the button from 2WD to 4WD and back, do the lights work and can you here it switch under the car at the tranfer case? If no lights or no sound ( engaging sound from transfer case motor), chances are a fuse (fuse located left penel of dash board), or the transfer case control module under passinger dash is bad, or the tranfer case engagement decoder motor could be bad. On Mine all this worked okay (continue).

2. Remove battery and battery tray. Below this is a vacuum actuator that locks the front wheel drive. If it is under total vacuum ( sucked in) it will indicate that the front wheels are locked in for 4WD ( when sucked in it pulls on a cable connected to the front differential). The signal for the front actuator to lock in the front wheels comes from a vacuum switch at the transfer case) If you remove the vacuum line the actuator will expand letting the cable relax and is one way to over ride the front wheels from being locked in, untill you can fix it. Mine was sucked in confirming that 4WD was always engaged.

This is what was wrong with mine; After confirming #2 above, I went to the vacuum switch located above the transfer case, it has a 3 vacuum line plug attached. On mine the ball at the end was (stuck in), as it should be sticking out under spring load. Went to Autozone and special ordered the swithch for about 27.00. I also removed the sensor switch in the front differential and found that the ball popped out and was stuck inside the cable linkage. I removed the ball and also replaced this switch for about 25.00 overnight special order.

I would check this all out first, there are other possible reasons like a sticking cable or internal probelm, but mine was very simple.

Just on the outside chance that your front drive shaft is not turning while in 2WD (as it is not suppose to), A vibration could be something else like front hub bearings, u-joints, etc.
Ken

 

Just a bit of further information to add to the post above.

The NV233/NP233 (3-button switch in the dash) transfer case will have the front drive shaft in float while in 2wd; meaning that it may not turn while driving and you should be able to turn it by hand.

The NV236/NP236 (4-button switch in the dash with auto4wd) transfer case has a preloaded clutch pack which will cause the front driveshaft to still move even while in 2wd. It comes down to what the OP has.

 

Thanks all will try these things in next couple of days......thanks