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Duke350
Duke350, Chevy Tech
Category: Chevy
Satisfied Customers: 86
Experience:  20 years in the automotive repair industry, Currently freelance
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2000 GMC: I have narrowed it down to the front differential

Customer Question

Hello,
I hope you can help... My 2000 GMC Jimmy S series has a noise in the r/f wheel area. I have narrowed it down to the front differential. Upon inspection it seemed the acuator wasnot fully engageing the 4wd. I then replaced the Vac Actuator and cable both new GMC parts. Still the same problem. When you pull the cable at the entry point on the differential it goes into 4wd but will not stay in 4wd when you let go. Also when it comes out it does not fully disengage making the noise like a clicking or racheting sound. Ther is a sensor at the differential where the cable goes in could that be the problem or I have heard it may be Thrust Washers? Where are the thrust washers and is it a tough repair? How complicated? I have checked the rest of the 4wd everything good Transfer sending power to the front differential via the front drive shaft. Nothing after that no front wheels turning when on four horses in the air. Please help what could it be? About 2 months ago the right side drive axel was replaced. When you disengage everything and disconnect the battery then put it together you can drive with no noise until you activate the 4wd then you disengage the 4wd since it doesn't lock in and the noise appears esspecially in reverse a strong clicking. Please help I really do not want to keep replacing parts that do not need replacement. Let me know [email protected] Thanks in advance,
                      John
Submitted: 10 years ago.
Category: Chevy
Expert:  Duke350 replied 10 years ago.
Do you have good vacuum going to the actuator? There is a vacuum switch on the transfer case for these, and they are prone to going out. Its a bit of a pain to switch out, but its fairly inexpensive. I think it was about $40 at the local GMC dealer.
Customer: replied 10 years ago.
Reply to Duke350's Post: You really did not answer the question.. I do not want to sound rude but, It is frustrating.
It has plenty of vacumn and it is a brand new actuator and cable. Do you any ideas the 4wd front shaft works just no front differential engageing to front axel's. Any ideas?
Expert:  Duke350 replied 10 years ago.

I understand your frustration. This was not meant to be an
answer, it was meant as a start for troubleshooting. I was just trying to
see if you were aware of the switch on the transfer case. Its job is to switch
the vacuum to the actuator (under the battery) on or off. This switch and the
actuator are normally the first parts to fail, and I just wanted you to check
them for me. Since you have a new actuator I want to eliminate the switch. To
check the switch you need to hook up a vacuum gauge to the line that goes to
the actuator and see how much it read while running with the car inXXXXXand what it reads inXXXXX