Just a few comments, some are opinions.

A Jake on an 8V92, as set up with 2 cylinders per bank has a maximum of 220 HP rquivalent braking. It is not equal to the force of a retarder.

However, in my opinion a Jake is a no cost effective means of slowing on a hill, and in my previous bus I could go down a steep grade and if the high setting slowed the bus too much, and the low setting not enough I could switch back and forth between the two to maintain the desired speed.

A Jake brake is most effective when the RPMs are higher, hence Orren's idea of downshifting makes perfect sense.

A retarder will heat the transmission fluid rapidly. It is taking the oil pasing through the transmission and making it work hydrauilically in the retarder section before entering the water to oil intercooler. The fluid temperature we see on our transmission temperature gauges is what we see immediately prior to the intercooler, or when it is at its hottest having done the work of retarding. This is not the temperature of the transmission fluid in the transmission.

However, while the transmission is not necessarily seeing overheated oil, those high temperatures do haven an impact on the life of the oil itself. The ATEC computer limits the discharge oil temperature to 300 degrees, and if it reaches or is about to exceed that value, the amount of retardation is diminished to maintain the fluid temperature at or below the 300 degree value.

It is my opinion both the Jake and the retarder require the driver to exercise control. The retarder however also requires the driver to try to limit the temperatures via whatever means is possible, and that is not only more work, but it requires a lot of attention in hilly or curvy roads.

The retarder switch can be left on, and the seven position stalk can be in the off position and the retarder will still engage proportional to the amount of braking force being used. The driver needs to monitor the transmission oil temperatures under hard braking even when the lever control is in the off position. The retarder has a significant impact on improving braking distances.

But I would take a Jake brake any day of the week.