If the timer was replaced and there was no improvement then the next possible cause of this problem would be the 8558178 electronic control. Refer to the image below for a picture of the wiring diagram.
Since there seems to be a problem with the timer turned off or on there is one check you might make to resolve this problem. Remember to unplug the dryer.
You replaced the timer so you know how to access the console. Access the electronic control and unplug the harness to it. With the harness unplugged and not touching anything plug the dryer back in and see if you hear the ticking or humming from the timer. If you don't then I'd suggest you change the control which is the most likely cause of your problems.
If you still hear the noises with the control disconnected then there is likely a short or pinched wire somewhere on the harness. This can be extremely difficult to locate and repair.
Another consideration is the expense to repair the dryer verses the expense of replacing it. The control is approximately $125 dollars and you have already bought a timer. Most service call charges start about $129 dollars so it can easily cost more to fix than to replace.
Just to give you an idea you can view a similar new gas dryer:
New Similar Dryer
If you need the 8558178 electronic control you can obtain it from the following site:
I hope this information is helpful to you in resolving this problem but submit another question with any additional details for further assistance.