the casing 32 but in this case the shell 33 is replaced by a different shell 45 that extends around the two bearings 28 and 29 and still supports the thrust collar 35 forming the attachment to the housing 30 the assembly is different from the assembly in fig2 it is made by fixing the housing 30 and then consists of inserting the gear 20 fitted with the bearing closest to it in this case 29 into the housing 30 placing it on a thrust surface 50 at the bottom of the housing 30 sliding the seal support sleeve 38 above the gear 20 and fixing it to the housing 30 the shell 45 fitted with the bearing on the remote side of the gear 20 in this case the ball bearing 28 is then inserted into the reaming in the housing 30 and around the hub 27 and the bearing 29 the bearing 28 supports a spacer ring 51 that finally touches the other bearing 29 during this movement pushes it back and thus lifts the gear 20 when the collar 35 stops in contact with the housing 30 the gear 20 engages with the crown wheel 21 the transmission shaft 25 is finally installed fig4 represents a variant of this idea in which bearings 28 and 29 occupy the same positions as in the previous design and in which the shell 33 is also used but the thrust collar 34 of the bearing 28 placed on the edge of the housing 30 is replaced by a collar 46 placed under it and the collar 35 of the shell 33 with which it is in contact the assembly is made approximately in the same way as before.