An agricultural tractor rear suspension has a driveshaft that is configured to resist suspension arm flexure by communicating tensile and compressive forces from the suspension arm to the tractor chassis. The LED at least includes a substrate, a saw-toothed multilayer, a first type semiconductor layer, an active emitting layer and a second type semiconductor layer. The attachment apparatus includes a fixture fitting that engages with a threaded aperture, such as a light socket, and a tension member provides tension force between the fixture fitting and the body member, forcing the body member against the open end of the fixture. The probe tip adapter is useable with both single ended and differential measurement probes.