Transfer case conversion kit

In a four-wheel drive vehicle wherein the forward pair of wheels is driven through one differential assembly and the rearward pair of wheels through another differential assembly there is a transfer case through which power originating in the engine is distributed, or transfered, to the two differential assemblies. In the transfer case there is normally a third differential mechanism to compensate for differences in performance between the forward pair of wheels and rearward pair of wheels during on-the-road travel. The conversion kit of the invention makes use of a direct power transfer component in the transfer case at a location taking the place of the third differential mechanism, previously removed from the case. A hand manipulated lever adjacent the driver's seat operably connected to an interlocking element in the conversion kit enables the vehicle operator, at will, to connect power from the power train to the forward pair of wheels and, when desired, to disconnect the power for on/off the road travel.

In view of the current popularity of four-wheel drive vehicles, especially 
adapted to off-the-highway travel, appreciable attention has been given to 
a mechanism capable of disengaging the drive on one of the pairs of 
wheels, usually the front pair, when four-wheel drive is not needed as, 
for example, when the vehicle is being driven over a smooth highway. Hubs 
at the wheels, capable of locking and unlocking the wheels from the axle 
at will, have been employed, usually for disengaging the front wheels, 
when only rear wheel traction is needed. This has the disadvantage of 
making it necessary for the vehicle operator to stop the vehicle and 
physically manipulate the locking hubs to the desired position. 
To obviate the need for such an adjustment, some developments have featured 
an interaxle differential to allow speed differences between front and 
rear axles when running on a paved surface. Although a disengagement 
expedient may be provided for disengaging power operation of one of the 
pairs of wheels, usually the front pair, the disengagement has invariably 
been one directed to the wheels only and not the drive train for the 
wheels, which has to continue in operation even though not in use. Such a 
drive train may include several gear sets, a U-joint shaft which attached 
axles, and other moving friction generating parts. Fuel that is consumed 
in performing work required to move such non-functioning parts is wasted 
fuel which could otherwise be used for traction. As a consequence, even 
though power may not be actually supplied to the forward pair of wheels, 
there continues to be power consumed and also wear on the moving parts. 
Other attempts to accomplish a disconnection of one of the pairs of wheels 
not needed for traction have been complex and for that reason high in cost 
and needful of appreciable maintenance. 
It is therefore among the objects to provide a new and improved transfer 
conversion mechanism for the transfer case of a four-wheel drive vehicle 
which comprises a simple, though relatively rigid, rotating power transfer 
component replacing various movable elements in the transfer case. 
Another object of the invention is to provide a new and improved transfer 
conversion mechanism of a type such that various movable parts are 
disengaged so as not to be moved while in idling attitude, thereby to 
minimize wear on the forward drive train. 
Still another object of the invention is to provide a new and improved 
transfer conversion mechanism for a four-wheel drive vehicle having 
substantially a minimum number of moving parts and of a minimum amount of 
high precision fabrication whereby to provide a conversion mechanism which 
can be produced at a lower cost than prior mechanisms. 
Still another object of the invention is to provide a new and improved 
transfer conversion mechanism for a four-wheel drive vehicle of such 
limited number of individual parts and simple installation as to be 
capable of installation in the drive train of a vehicle by persons of no 
more than modest skill. 
Still further among the objects of the invention is to provide a new and 
improved transfer conversion mechanism for four-wheel drive vehicles 
capable of connecting the drive train to the forward pair of wheels and 
subsequently disconnecting the forward pair of wheels at will by a simple 
lever action. 
With these and other objects in view, the invention consists of the 
construction, arrangement, and combination of the various parts of the 
device serving as an example only of one or more embodiments of the 
invention, whereby the objects contemplated are attained, as hereinafter 
disclosed in the specification and drawings, and pointed out in the 
appended claims.

For a better understanding of the invention, there is shown in FIGS. 1 and 
2 a currently available mechanism customarily identified as a differential 
assembly mounted within a transfer case or housing indicated generally by 
the reference character 10 consisting of a central section 11 housing a 
central chamber 12 and, as herein designated, a main section 13 housing a 
main chamber 14, a cap section 15 housing a cap chamber 16, and an end 
section 17 housing an end chamber 18. For providing power to a 
differential transfer assembly 19, there is a drive shaft 20 rotatably 
mounted within a bearing race 21 in a bearing ring 22 clamped between the 
end section 17 and the central section 11. 
Non-rotatably mounted on a splined band 23 is an annular collar 24 on which 
are four radially extending pins 25, each of which freely rotates a pinion 
26. The pins 25 extend radially outwardly into apertures 27 and 28 on 
respective carrier members 29 and 30. Bolts 31 may be employed to anchor 
the carrier members 29 and 30 in engaged position. 
Rotating with the pinions 26 is a rear wheel output shaft 35 provided with 
a beveled crown gear 36. A bearing ring 37 rotatably supports the output 
shaft 35 in the cap section 15. A yoke 38 splined to the output shaft 35 
is the means by which the rear pair of wheels (not shown) of the vehicle 
are driven through their own differential. 
On the opposite side a front wheel output shaft 40 has a crown gear 41 
rotating with the same pinions 26, the front wheel output being rotatably 
supported upon a bearing 42 on the drive shaft 20. Splined to the output 
shaft 40 is a sprocket 43 around which passes a drive chain 44, the chain 
engaging a sprocket 45 for rotating a shaft 46 on which is a yoke 47 
adapted to be attached in driving relationship with a pair of front wheels 
(not shown) of the vehicle. 
In the relationship described, the front and rear yokes are in full-time 
drive position which means that all four wheels, namely, the rear pair and 
front pair wheels, are being driven through the differential transfer 
assembly 19. This would be the desirable adjustment for off-the-road 
transportation of the vehicle. 
To change the relative position of the parts, there is provided a slider 50 
splined upon the front wheel output shaft gear 40 but slidable with 
relation to it. A spring 51 bottomed on a shoulder 52 in the slider and 
against the crown gear 41 normally holds the slider in the position of 
FIG. 2 wherein teeth 53 of the slider are out of engagement with 
complementary teeth 54 of the carrier member 29. By manipulation of a 
conventional lever (not shown), terminating in a fork 55, the slider can 
be moved against tension of the spring 51 so that the teeth 53 engage the 
teeth 54. Under those circumstances the front wheel output shaft 40 is 
by-passed and the sprocket 43 directly driven from the drive shaft 20 
through the carrier members 29 and 30, with rotation of the pinions 26 
being frozen. 
An embodiment of the invention chosen for the purpose of illustration is 
shown located in the same housing 10 and activated by the same drive shaft 
20, as has been previously made reference to, and wherein the front wheel 
output shaft gear 40 is in splined relationship with the sprocket 43. The 
drive shaft 20, by having been provided with circumferential splines 23, 
has a direct drive splined engagement with a conversion shaft component 
61. The conversion shaft component 61 comprises in part an assembly 
bracket 62 serving as a carrier member. The assembly bracket 62 is adapted 
to be anchored to the carrier member 29, or 63 as identified in FIGS. 3 
and 6, by use of roll pins 64, extending through spokes 67, the carrier 
member 63 being the same as the carrier member 29 previously made 
reference to. In the carrier member 63 are recesses 65 complementary with 
respect to recesses 66 in the assembly bracket 62. The recesses are for 
accommodation of spokes 67 which are carried by the carrier member 62. A 
portion 68 of the conversion shaft component 61, rotatably supported in a 
partition 69 forming part of the main section 13, is provided with 
circumferentially extending splines 70 which are adapted to non-rotatably 
attach the yoke 38 to the conversion shaft component 61. 
Within the left end of the conversion shaft component 61 is a recess 71. 
Interior splines 72 are adapted for splined engagement with the splines 23 
of the drive shaft 20. A pocket 73 rotatably receives an extension 74 of 
the drive shaft 20 so as to provide a bearing support for the drive shaft. 
Acting together the assembly bracket 62 and carrier member 29 provide a 
chamber 75 within which is located a thrust bearing 76. The thrust bearing 
extends around a concentric inner portion 77 of the conversion shaft 
component 61. In the embodiment shown by way of example, the thrust 
bearing 76 consists of inner and outer washers 78 and 79 separated by a 
bearing race 80 provided with ball bearings 81. The thrust bearing 76 
provides for endwise thrust of the front wheel output shaft gear 40 which 
must be provided with a degree of end play. 
In the form of invention of FIG. 7, the spokes 67 are dispensed with. For 
attaching the carrier member 63 and assembly bracket 62 together to serve 
as a unit, bolts 82 having heads 83 concealed within the recesses 84 in 
the assembly bracket 62 extend through bolt holes 84 into threaded holes 
85 of the carrier member 63. 
From the foregoing description it will be clear that the drive shaft 20 is 
connected by a direct drive connection to the conversion shaft component 
61 by the splines 23 and 72. In normal position of the slider 50, as shown 
in FIG. 3, and also FIG. 7, there is no drive connection between the drive 
shaft 20 and the sprocket 43. This is because the front wheel output shaft 
40 rotates freely upon the bearing 42 and the drive shaft 20. As a 
consequence, all of the power generated in the drive shaft 20 is carried 
directly to the rear yoke 38 for driving the rear wheels of the vehicle. 
The yoke 47 idles and accordingly the front wheels of the vehicle will 
also idle, or rotate freely, as the vehicle is moved by operation of the 
rear wheels. 
When the transfer case conversion kit is to be employed to convert from 
two-wheel drive to four-wheel drive, the fork 55 is manipulated by its 
associated lever (not shown) so as to shift the slider 50 from the 
left-hand normal position of FIG. 3 to the right-hand extended position of 
FIG. 6 against tension of the spring 51. In this position the teeth 53 of 
the slider engage the teeth 54 of the carrier member 63. Since, in effect, 
the carrier member 63 and assembly bracket 62 non-rotatably engage each 
other by action of the spokes 67, the slider 50 is rotatably driven by 
action of the drive shaft 20 through the conversion shaft component 61. 
Since the slider is connected by splines 86 and 87 to the front wheel 
output shaft gear 40, which is in turn splined to the sprocket 43, the 
sprocket 43 will then drive the chain 44 and as a consequence the yoke 47 
will be rotated, which is the yoke for driving the forward pair of wheels. 
The arrangement just described is for off-the-road travel. When the 
vehicle is to again be made ready for on-the-road travel, the yoke 47 can 
be disengaged from a driving relationship by shifting the fork 55 in a 
direction from right to left, as viewed in FIGS. 3 and 6. When this is 
done, the spring 51 will expand and move the slider 50 from right to left, 
as viewed in FIGS. 3 and 6, a distance sufficient to disengage the teeth 
53 from the teeth 54. This is the position of FIG. 3. In this position 
there is no driving relationship between the drive shaft 20 and the 
sprocket 43. Accordingly, therefore, the yoke 47 runs free as does also 
the forward pair of wheels. 
In the embodiment of the invention of FIG. 8 an assembly bracket 88 has an 
axial length substantially the same as the aggregate axial length of both 
of the carrier members 29 and 30 of FIGS. 1 and 2. The bracket 88 is 
integral with the conversion shaft component 89 on one side and provides a 
chamber 90 on the opposite side. At the edge of the chamber 90 are 
circumferentially disposed teeth 91 which are complementary with respect 
to teeth 53 of the slider 50. The same thrust bearing 76 may also be used 
with the embodiment of the device. 
While particular embodiments of the present invention have been shown and 
described, it will be obvious to those skilled in the art that changes and 
modifications may be made without departing from the invention in its 
broader aspects, and therefore, the aim of its appended claims is to cover 
all such changes and modifications as fall within the true spirit and 
scope of the invention.