2004 Chevy Express 3500 transmission will only shift into reverse the shifter will not go any further

It won't crank because it is in reverse. First remove the linkage at the transmission and put it in park or just see if the transmission shifter will move. If it does, then look to the cable or shifter in the console/column. If the transmission shifter doesn't move, It is an internal transmission problem. Most can be repaired by removing the valve body. Via the transmission oil pan. Some the transmission has to be pulled .

Does it shift into park and reverse with the shifter disconnected ?
Both the shifter and the actual transmission ?

Rock the car back and forth to remove parking pin from park .

One suggestion is to use a syphon pump via the filler tube. Another is to disconnect one of the cooler lines going to the radiator.

check your wheel speed sensor to make sure it is operating correctly if it is bad it will send signals to tranny making late shift and causing hard shift

if its a 5 speed, yes the shifting is loser than normal cars. the reverse is all jacked up.. if its anything like my 06 aveo when you shift into reverse you have to lift the little circle thing on your shifter up ad act like your putting it into first.. If it grinds try doing it slower. I HATE this transmission. Chevy did a horrible job on picking it. I always grind reverse no matter what

if you have specific details as to the times , rpms , conditions that cause the problems take it to an accredited auto transmission specialist shop and have it diagnosed
with your details they should be able to pinpoint the fault as it will not be uncommon

CHECK MAKE SURE BRAKE LIGHT SWITCH FUSE OR NEUTRAL SAFETY FUSE HAS BLOWN.IF ALL IS GOOD.PROBLEM IS IN MANUAL SHIFT CABLE.OR THE TRANSMISSION RANGE SWITCH OR NEUTRAL SWITCH IS BAD.

if ur replacing it remove front grill disconnect both lines and carefully remove retaining clips from radiator if replacement is original eguipt mount & reconnect --if its a universal follow instructions usually cut off fittings and use clamps and hose to hook up

To isolate the problem as either an internal transmission problem,or external to the transmission,(shifter or cable malfunction),the shifter cables should be disconnected from the transmission.On the transmission are two levers,if you have a 5 speed trans.One is the neutral gate lever,and the other is actual gear shift lever.Manipulating the levers manually,see if the transmission will engage into Reverse gear.If the transmission engages into Reverse gear,then the problem is either in the shifter mechanism itself,or the shift cables.If the transmission will not engage into Reverse gear,then the problem is either an internal problem,or possibly a switch seized up,like the reverse gear indicator switch.At this point,i would have an assistant sit in the car,engine off,and run through all the gear selections with the shifter,while watching and looking for a cable not operating to its full stroke.Take the console apart to access the shifter mechanism and visually inspect the assembly.Disconnect the cables and operate them manually,one at a time,while an assistant watches them underhood.Visually inspect the shifter and it's mechanism for a broken,cracked,or damaged component.At this point,the problem should be identified and repaired as either cable or shifter malfunction.