I had heard that the PTO option is quite cheap when ordered with a new truck, if only I knew when I ordered mine.

There are a few big advantages to having the retarder fitted to the PTO rather than the rear drive shaft.

Firstly, you do not reduce the ground clearance.

Secondly, the braking force is applied to both the front and rear axles (32%/68% due to the center differential) and with the center diff locked 50%/50%.

Thirdly, due to the gearing the half gears and low range make the retarder more powerful. In high range without the half gears the retarder performs the same as having it on the rear drive shaft. With the half gear engaged it becomes approximately 24% more powerful - this is how I use it for hills. In low range it becomes 310% more powerful and low range with half gears 388% more powerful which will throw you into the windscreen ;-) It is amazing for off road steep descents.

It is worth remembering that the retarder on its own will not lock the wheels, the slower the axles turn the less powerful the retarder becomes. This makes it great off road as you will not lock up a wheel using the retarder. However, light braking can make the rear wheels lock on steep loose surfaces, which triggers the ABS, which in turn turns off the retarder and is quite scary! I have installed a switch to turn off the ABS when off road. I know the ABS gets turned off when the center differential is locked but I find the truck handles well (much smaller turning circle) with the center differential unlocked. As my loading is about 32%/68% the torque split in the diff is perfect and does not need locking until the conditions gets really bad.

Last edited by Marcus Tuck; 01/07/2016 17:35.