Changing from four wheel drive to two wheel drive

Tiny
TOMMY2DEER
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • 6.8L
  • V8
  • 140,000 MILES
It goes into four wheel drive and drives okay, but when I go back to two wheel drive it will not go to two wheel drive until I drive about one hundred yards and then I hear a loud clang and get a jerk. Now it is in two wheel drive and all is okay. It does this every time I go to four wheel drive.
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Saturday, March 4th, 2017 AT 12:04 AM

4 Replies

Tiny
HMAC300
  • EXPERT
It may be from the wrong axle ratio. The front and rear must be the same ratio or you get t-case windup which it sounds like. If either axle was replaced gear wise can cause this. If you open up axle it should be stamped on ring gear if stock what ratio it is along with a tag on right rear on rear axle. It may also be your automatic hubs are not unlocking so check those for wear.
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Saturday, March 4th, 2017 AT 7:55 AM
Tiny
STEVE W.
  • EXPERT
Have seen the same problem on a few GM 4X4's. (My 2002 Blazer is currently a sufferer of it, just do not want to tear into it now).

On the ones I have repaired it was due to the front axle interlock not releasing properly. It causes pressure in the drive line that does not allow the T-Case motor to disengage the case. Then the coupling finally slips enough that the splines uncouple. The T-case makes a bang as the torque is released. On most of them the actuator seemed to be the initial cause of the problem. It was not engaging properly and damaged the end of the splines so the collar could not slide freely.

On my Blazer you can see and feel it when it releases, Feels like you hit a low speed bump and whacked a garbage can at the same time.
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Saturday, March 4th, 2017 AT 8:31 AM
Tiny
TOMMY2DEER
  • MEMBER
I do not use four very much, just to get the boat up a slippery ramp, etc. Is it okay if I just live with it or am I in danger of breaking something more expensive?
I guess everything is already in a lubricated environment.
You guys are great! Thank you! I will make a donation.
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Monday, March 6th, 2017 AT 8:12 AM
Tiny
STEVE W.
  • EXPERT
It sends a big shock through the transfer case and can break the chain or damage the front axle. On customer vehicles I generally use OEM repairs.

On yours it has the wax powered unit which is real easy to replace, it is literally a five minute job. But if it is internal wear that likely will not help.

It can be replaced with a cable or you can go the other way and install a plug that locks the front axle full time. On mine I am going to be changing the vacuum axle unit out for a more reliable mechanical cable control.
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Monday, March 6th, 2017 AT 9:19 AM

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