fig1 to 3 show an embodiment of the invention . in fig1 and 2 , reference numeral 2 denotes a transmission for 4 - wheel drive , 4 indicates a front side differential gear for final deceleration , and 6 a transfer mechanism . the transmission 2 is coupled with the differential gear 4 for rotating front wheels ( not shown ) via a drive shaft . the transfer mechanism 6 coupled with the differential gear 4 has therein a transfer shaft 8 . a ring ( i . e . bevel ) gear 10 is attached to one end 8a of the transfer shaft 8 and a driven gear 12 is attached to the other end 8b . therefore , the transfer mechanism 6 , which distributes the driving force of the internal combustion engine , outputs the driving force which is transferred from the transmission 2 by the driven gear 12 which engages with a final deceleration gear 14 of the front side of differential gear 4 to cause rotation of a rotational shaft 18 via a transfer bevel gear 16 , the ring gear 10 and the transfer shaft 8 . the driving force which is output from the rotational shaft 18 is transferred to rear wheels ( not shown ) via a propeller shaft ( not shown ) connected through a coupler 20 , a rear side differential gear , and the like . an annular oil sealing portion 22 which partitions and separates the transfer mechanism 6 and the front side differential gear 4 is provided on the transfer shaft 8 . explaining in detail , a large diameter hub portion 24 is formed on a portion of the transfer shaft 8 located generally centrally between the ends 8a and 8b , and the annular oil sealing portion 22 is arranged radially between a housing 26 , which surrounds the front side differential gear 4 and transfer mechanism 6 , and the large diameter portion 24 . the inside of the housing 26 is partitioned and separated by the oil sealing portion 22 into a first space portion 28 on the side of differential gear 4 and a second space portion 30 on the side of the transfer mechanism 6 . as shown in fig3 the oil sealing portion 22 is formed in a double lip shape by an interior shape - holding metal ring portion 32 , a holding portion to hold the metal portion 32 , and two annular springs 36 - 1 and 36 - 2 . the shape holding metal portion 32 has a hollow , generally t - shaped radial profile . the oil seal 22 has a seal member 34 of a rubberlike or elastomeric material wrapped closely around and closely conforming to this t shape . the annular springs 36 - 1 and 36 - 2 are received in radially outwardly opening grooves formed in lip parts 34 - 1 and 34 - 2 of the oil seal member 34 which extend axially oppositely from the base of the t . the annular springs 36 - 1 and 36 - 2 function to securely hold the lip parts 34 - 1 and 34 - 2 in snugly surrounding relationship on the outer peripheral surface of the large diameter portion 24 . the base of the t rests on the large diameter portion 24 , whereby the lip parts 34 - 1 and 34 - 2 create a snug sliding seal with the hub portion 24 . automatic transmission fluid ( atf ) of low viscosity is supplied as a lubricating oil into the first space portion 28 , and a gear oil serving as a lubricating oil of high viscosity is supplied into the second space portion 30 on the side of the transfer mechanism 6 . when the final deceleration gear 14 of the front side differential gear 4 is rotated by the driving of the internal combustion engine ( not shown ), the low viscosity atf in the first space portion 28 is lifted up , thereby lubricating the gear engaging portion of the transmission 2 and the other portions . on the other hand , when the transfer shaft 8 of the transfer mechanism 6 is rotated by the driven gear 12 as engaged with the final deceleration gear 14 , the high viscosity gear oil in the second space portion 30 is lifted up by the ring gear 10 and supplied to the bearing portions of the rotational shafts 8 and 18 . thus , the low viscosity atf can be supplied into the first space portion 28 , and the high viscosity gear oil can be supplied into the second space portion 30 on the transfer mechanism 6 side . a change in oil level can be reduced . the engaging portions of the gears such as transfer bevel gear 16 and the like and the bearing portions can be efficiently lubricated . moreover , as compared with the conventional transmission using only low viscosity atf , the required quantity of atf is reduced and fouling of the atf can also be decreased . on the other hand , because the oil sealing portion 22 partitions and separates the inside of housing 26 into the first and second space portions 28 and 30 , each lubricating path can be reduced and the lubricating efficiency can be improved . further , lubricating oils of different viscosities other than atf and gear oil can also be supplied into the first and second space portions 28 and 30 , so that the optimum lubricating oils suitable for the gears and bearings can be supplied , which is practically advantageous . furthermore , by arranging the annular oil sealing portion 22 between the housing 26 and the large diameter portion 24 on the central part of the transfer shaft 8 , the oil sealing portion 22 contributes to vibration - proofing and strengthening of the transfer shaft 8 . on the other hand , since the front side differential gear 4 and the transfer mechanism 6 can be integrated , the weight can be reduced and the size can be miniaturized as compared with the apparatus in which they are separately formed . the layout of the automatic transmission and the layout of the manual transmission are almost the same . the parts of the propeller shaft , rear side differential gear , and the like can be made common to both automatic and manual transmissions , which is economically advantageous . moreover , by merely exchanging and attaching a bottom casing b and a transfer casing c below a line segment a in fig2 it is also possible to change from a 4 - wheel drive to a 2 - wheel drive . the invention is not limited to the foregoing embodiment but many variations and modifications are possible . for instance , in the embodiment of the invention , the annular oil sealing portion 22 has been interposed between the housing 26 and the large diameter hub portion 24 on the transfer shaft 8 . however , as shown in fig4 it is also possible to provide a bearing 40 on the transfer shaft 8 , with the annular oil sealing portion 22 interposed between the bearing 40 and the housing 26 . on the other hand , the embodiment of the invention has been described with respect to an automatic transmission which has low viscosity atf in the first space portion thereof . however , the invention is also applicable to manual transmissions . although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes , it will be recognized that variations or modifications of the disclosed apparatus , including the rearrangement of parts , lie within the scope of the present invention .