Q. Will this replace a 1N4744 diode
A. Hi Stan. Thank you for your question. A 1N4744 is a 1W 15V Zener diode compared to the 1N4004 which is a 400V 1A diode so a very different set of characteristics. Depending what the application was it may be ok but unlikely. 47-5102 is a 1.3W 15V zener diode so a better match and only slightly higher rated – currently on clearance.