One problem related to transmission not go into gear has been reported for the 2004 Chevrolet Suburban. The most recently reported issues are listed below.
The vehicle is a 4wd Suburban 1500. With 2 wd drive selected and driving at varios speeds from 5 mph to 60 mph the vehicle will go into neutral. This has happened 7 or 8 times. Each time was in traffic which required illuninating emergency flashers and pulling to side of road. Every time presented a safety issue and was fortunate it didn't cause an accident. On one occasion I had just passed a semi on the intersate and had just pulled back into trucks lane when it occurred. Dealership could not detect a problem. The gear shift selector remains in "drive", the dash selector remains illuminated in 2wd and I get no messages on instrument panel message center. To troubleshoot I selected "auto 4 wd" on dash selector and operated for a week with no problem. I then selected 2 wd and the problem reappeared within 2 hours of operation. Once I stopped, I selected 1,2,3 and r on gear selector with no effect. Selected neutral and turned ignition off and then restarted with no effect (on previous occassion I had selected park with vehicle running and noticed a gear grinding noise so didn't want to do that again with engine running). Turned ignition off with gear selector in neutral and selected auto 4 wd and then restarted engine which took care of problem.