[SkiPow]

I posted this earlier on another thread. However, I am hoping that the tech guys can help me. My '04 2500HD duramax makes an audible clunk as I shift it into 4 hi on the fly. It doesn't do this at rest. My dealer can't find anything wrong with the front splines or with the fluid in the transfer case.
Any suggestions?

 

[DURAtotheMAX]

I wouldnt worry about it...its just the front axle engaging. The clunk is most likely from the gears and synchro's meshing and engaging. If you completely let off the pedal, and then press the 4x4 button it might clunk a little less. I noticed when I take all the strain off it by doing this, it doesnt clunk as loudly. Also make sure you are steering straight when you engage 4wd and after you press the button, steer back and forth once slightly to make sure all the wheels are spinning the right speed and the 4x4 can properly engage...

--Ben

 

[SkiPow]

I wouldn't worry about this if it had done this from the very beginning. However, it just started doing this a few weeks ago. My truck has 37,000 miles on it, so it is out of factory warranty; I do have an extended warranty, but it won't pay for anything unless it is broken. I don't want to wait that long. Would it help if I changed the fluid in the front diffential and in the transfer case to a synthetic? The manual says synthetic can be used for this type of 4 X 4 system.

 

[DURAtotheMAX]

hmmm might want to talk to Eric (Dmaxallitech)

 

[66flh]

The tires arent spinning when you engage 4x4 are they?

 

[jchunts92]

I have a 2002 Duramax with the Allison and I had the same problem with the transfer case making a sound and just like you said I took it to a garage, and they didn't know what it was either, and now the transfer case won't engage the front drive shaft.