Brother HL-4040CN, HL-4050CDN, HL-4070CDW Service Manual page 255

(9) Remove the Extension spring LT from the Spring hook and remove the Gear 46/55 from
the Drive unit by releasing the Hook.
Drive unit
Hook
Spring hook
Extension spring LT
(10) Remove the Gear 46 LT from the Drive unit.
Drive unit
Gear 46 LT
<Left side>
Gear 46/55
Fig. 3-226
<Left side>
Fig. 3-227
3-146 Confidential