How do your replace the timer?
Here are your parts
http://www.appliancepartspros.com/partsearch/modelsearch.aspx?model=mde7400ayw
The following should help with the repair
http://appliancedigest.com/index.php?/files/go/bc3daec2a95c11865f5550f576ce6855/16023110-maytag-sloped-front-dryer-repair-service-manual
You have to join the site to download the manual but it is free and this is a very good site for manuals and other info for the appliance repair DIYer.
You did not say why you wanted to replace it but if the timer does not work in auto modes but does work in timed dry then I doubt the timer is the problem.