Luis,
The flashing gear indicator is the classic symptom of a failed NSBU switch (on the Allison). You can point your dealer service people in this direction when you take it in, or, if you're out of warranty, you can replace it yourself by buying an improved model of the switch at an Allison dealer for about $50. Do a search on NSBU here.
[ 02-02-2003: Message edited by: pinehill ]</p>
2001 2500HD D/A CC/SB 4x4<br />A.R.E. Z-series topper, CA 75-series boards, Bedrug, Fumoto valve, Amsoil air filter, Jan \'02 PCM updates,Transfer Flow 50 gal. crossbed aux. fuel tank, Bilstein shocks, 25 ft. Tahoe Transport toybox (9.6K loaded), Hensley hitch, Tekonsha Prodigy brake controller.