Different types of retarders

[126th street]

RE: Different types of retarders
All ZF and Voith retarders are mounted inside the gearbox and are hydraulic. In ZF-equipped buses there is often a dash-mounted gearbox temperature indicator and when the retarder is used this rises, sometimes a great deal for example when used when going downhill for a prolonged period.

Voith retarders are very powerful and can in the right hands slow a bus to walking pace without using the brakes.

Electric retarders were seen many years ago (this is what a Telma is) and were little more than a large magnet around the prop-shaft and were generally only used on coaches. Nowadays coaches use either gearbox-mounted examples in the case of fully-automatics, or exhaust/engine brakes in those which are manuals or have automated manual transmissions. The latter are easily identifiable as the engine or exhaust brake cuts in momentarily when changing up a gear to slow the engine down quickly and allow a quicker shift.