A utility vehicle includes a rear frame, a front frame and a coupling body. A height of a vertical section of the front frame is shorter than a height of a vertical section of the rear frame tube, and a ground clearance of an upper face of the front frame tube is shorter than a ground clearance of an upper face of the rear frame. The coupling body connects a rear end of the front frame with a front end of the rear frame. An upper face member of the coupling body includes a forwardly descending sloped face that interconnects an upper face of the rear frame with an upper face of the front frame. A front differential unit is mounted on the front frame. A front drive shaft having a constant velocity joint extends from the front differential unit forwardly of the coupling body and upwardly of the front frame.

A vehicle front structure includes side rails, rail tips, and a tension member. The side rails extend longitudinally in a front portion of the vehicle on left and right sides of a central longitudinal axis of the vehicle. The rail tips have a plurality of flat walls that define a hollow polygonal body disposed about a tip axis. The rail tips have proximal and distal ends. The proximal end is fixedly coupled to a forward terminal end of the side rail inboard of an outer quarter of a total vehicle width. The rail tip extends outboard and forward such that the distal end is disposed within the outer quarter. The flat walls have a forward wall thickness that is less than a rearward wall thickness. The tension member is fixedly coupled to the distal ends and spans laterally therebetween.

A vehicle front structure includes side rails, rail tips, and a tension member. The side rails extend longitudinally in a front portion of the vehicle on left and right sides of a central longitudinal axis of the vehicle. The rail tips have a plurality of flat walls that define a hollow polygonal body disposed about a tip axis. The rail tips have proximal and distal ends. The proximal end is fixedly coupled to a forward terminal end of the side rail inboard of an outer quarter of a total vehicle width. The rail tip extends outboard and forward such that the distal end is disposed within the outer quarter. The flat walls have a forward wall thickness that is less than a rearward wall thickness. The tension member is fixedly coupled to the distal ends and spans laterally therebetween.

A pair of elongate attachment members, or Z-rails for attaching an end of a trailer crossmember to a flanged beam each include a first end section, an L-shaped portion comprising a horizontal leg and a vertical leg extending from the first end section, and a second end section extending from the vertical leg. The horizontal leg has a bottom surface with a width equal to the distance between the web of the flanged beam and the end of the flange. The vertical leg has an outer surface with a width equal to the width of the end of the flange. The Z-rails are attached to opposite ends of the crossmember to form a subassembly. The subassembly is fixed to and between the flanged beams by welding the first end sections to the web of the corresponding beam, with the horizontal leg on the flange, without directly heating the flange, thereby not diminishing the toughness of the flange.

A vehicle underbody assembly including a pair of rockers, a pair of rear rails, a first cross member, and a second cross member is provided. Each of the pair or rear rails extends from one of the rockers and each includes a rear portion, a first mid-portion, a second mid-portion, and a forward portion. Each of the forward portions is secured to one of the rockers at one of a first joint and a second joint. The first cross member extends between the rear rails at a transition region between the second mid-portion and the forward portion. The second cross member extends between the rear rails at locations adjacent the first and second joints. Each of the rear rails is thermally treated so that the second mid-portions form a hard strength zone. The hard strength zone may further be defined as a zone having a fully martensitic microstructure.

A vehicle underbody assembly including a pair of rockers, a pair of rear rails, a first cross member, and a second cross member is provided. Each of the pair or rear rails extends from one of the rockers and each includes a rear portion, a first mid-portion, a second mid-portion, and a forward portion. Each of the forward portions is secured to one of the rockers at one of a first joint and a second joint. The first cross member extends between the rear rails at a transition region between the second mid-portion and the forward portion. The second cross member extends between the rear rails at locations adjacent the first and second joints. Each of the rear rails is thermally treated so that the second mid-portions form a hard strength zone. The hard strength zone may further be defined as a zone having a fully martensitic microstructure.

In a vehicle frame structure, upper ends of a front frame and a rear frame, which connect a lower frame and an upper frame vertically, are connected to each other above the upper frame, and a front portion frame assembly is connected to a main frame assembly via the lower frame and the upper ends of the front and rear frames. A bumper includes a front-rear frame portion extending forward from the front frame, and an inclined frame portion arranged between an intermediate portion of the front frame and an end portion of the front-rear frame portion. The bumper includes a sub-bumper, the sub-bumper including a front sub-frame extending upward from a front end of the bumper, and a front-rear sub-frame connected between an end portion of the front sub-frame and an intermediate portion of the front frame above the upper frame.

In a vehicle frame structure, upper ends of a front frame and a rear frame, which connect a lower frame and an upper frame vertically, are connected to each other above the upper frame, and a front portion frame assembly is connected to a main frame assembly via the lower frame and the upper ends of the front and rear frames. A bumper includes a front-rear frame portion extending forward from the front frame, and an inclined frame portion arranged between an intermediate portion of the front frame and an end portion of the front-rear frame portion. The bumper includes a sub-bumper, the sub-bumper including a front sub-frame extending upward from a front end of the bumper, and a front-rear sub-frame connected between an end portion of the front sub-frame and an intermediate portion of the front frame above the upper frame.

A vehicle underbody assembly including a pair of rockers, a pair of side rails, a first cross member, a second cross member, and a fuel tank is provided. Each of the pair of side rails is secured to a rearward portion of one of the rockers. The first cross member extends between the side rails and is thermally treated to form a first central hard strength zone between two first soft strength zones. The second cross member is arranged with the pair of side rails and the first cross member to form a rectilinear frame and is thermally treated to form a second central hard strength zone between two second soft strength zones. The fuel tank is secured between the pair of side rails so that the fuel tank is located within a rectilinear frame formed by the pair of side rails and the cross members.

A vehicle underbody assembly including a pair of rockers, a pair of side rails, a first cross member, a second cross member, and a fuel tank is provided. Each of the pair of side rails is secured to a rearward portion of one of the rockers. The first cross member extends between the side rails and is thermally treated to form a first central hard strength zone between two first soft strength zones. The second cross member is arranged with the pair of side rails and the first cross member to form a rectilinear frame and is thermally treated to form a second central hard strength zone between two second soft strength zones. The fuel tank is secured between the pair of side rails so that the fuel tank is located within a rectilinear frame formed by the pair of side rails and the cross members.