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goodwrench9124, ASE Certified Technician
Category: Chevy
Satisfied Customers: 3432
Experience:  Ase Master Certified, GM Master Certified Tech. Awarded GM Top performer, Hybrid certified
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i have a 2001 chevy astro van with a service AWD light that

Customer Question

i have a 2001 chevy astro van with a service AWD light that comes on at start up but not all the time. The guy I got it from said a dealer said they might need to replace the TCCM . I used to be a mechanic years ago. How do I toubleshoot the TCCM? Is there a fuse I can pull or remove a wire harness from the TCCM? The vehicle vibrates at 50+ on DECELERATION. It is getting poor milage to me it feels like it is stuck in AWD. 113,000 miles on the vehicle ujoints seem fine vibration is in the center floor portion and everyone in the vehicle can feel it. I also checked the front CV joint on the front driveshaft and it has about 1/4 or less lateral play in it. please respond
Submitted: 8 years ago.
Category: Chevy
Expert:  goodwrench9124 replied 8 years ago.
Hello, and welcome. do you know what trouble code was stored in the system?
Customer: replied 8 years ago.
I was told when I bought it that know trouble codes were stored. I went to the local auto parts store that allows people to use thier code reader and found know trouble codes stored to follow up what the previous owner said
Expert:  goodwrench9124 replied 8 years ago.
Ok, most parts stores code readers only read engine codes. that normally are not able to read transfer case module codes.this requires a high end scan tool like the dealers use. there are 10 different possible codes. without this code it would be hard to say where the problem lays. but the shuddering you are getting is usaully just related to the fluid and most of the time doesnt cause a warning light issue. changing the transfer case fluid with GM's auto trak fluid does repair the shudder problem
goodwrench9124 and 4 other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
so you are saying the fluid is bad that is in there? does it wear out? did gm put the wrong stuff in there? it only has 113,000 or so on it I will change the fluid and get the codes read thanks
Expert:  goodwrench9124 replied 8 years ago.

ok, let me know what the code is, here is the info on the fluid.


Transfer Case Shudder (Flush and Replace Transfer Case Fluid)

Subject:Transfer Case Shudder (Flush and Replace Transfer Case Fluid)

Models:1999-2005 Chevrolet Astro (AWD)
1999-2005 GMC Safari (AWD)
1999-2001 Oldsmobile Bravada
with All-Wheel Drive (NV136) Transfer Case (RPO NP4)


  • Drain the transfer case fluid.
  • Refill the transfer case with 2 L (2 qts) of new fluid, P/N 12378508 (Canadian P/N 10953626).
  • After refilling the transfer case, drive the vehicle a minimum of 8 km (5 mi).
  • With the transfer case at operating temperature, drain the transfer case fluid again.
  • Refill the transfer case with new fluid.
  • Important: The vehicle may require approximately 160 km (100 miles) of driving before the condition is completely corrected.