All Hannigan Trikes use a 7.5 inch Ford Thunderbird differential with 2.73 gears matched to right-size tires to maintain the original bike ratio, except for the Hannigan Harley-Davidson® FLH series Trike conversion, which uses the original H-D belt drive and sprocket.<br />
<br />
The above was taking from the Hannigan website. See link below.<br />
<br />
<a href="http://www.hannigantrikes.com/content/whyhannigan.html" target="_blank">Why buy a Hannigan Trike?</a>