ZF 6-Speed

High operating temperatures increase the lubricant's rate of oxidation and shorten its effective life. When the average operating temperature is high, the transmission may require more frequent fluid changes or external cooling. External oil coolers are used to reduce high operating temperatures. The following conditions in any combination can cause high operating temperatures:
^ Operating consistently at slow speeds.
^ High ambient temperatures.
^ Restricted air flow around the transmission.
^ Exhaust system too close to the transmission.