Programming – Gear Fast/Run Slow & Gear Fast/Run Super Slow

Gear Fast/Run Slow (GFRS) and Gear Fast/Run Super Slow (GFRSS) are specing methods to promote improved fuel economy through lower engine speed and faster gearing. GFRS/GFRSS only applies for a multi-torque rating allowing at least a 1750 lb-ft upper torque value. In addition, the Eaton-Fuller RTOC-16909A Convertible 9(10) – Top 2 transmission must be used (see Eaton Top 2 details on page 72-74).

GFRS/GFRSS is applicable for van, reefer, and tanker applications, with a GCW of 80,000 lbs. The following table matches axle ratios with the appropriate drive axle tires revolutions per mile, specifically for the GFRSS designation. A GFRS table is not included, however, the only difference is an increased engine rpm.

While GFRS/GFRSS is not an electronically-programmable parameter, it has been included in this handbook to supplement the Eaton Top 2 transmission programming section on page 72-74. The results of employing GFRS/GFRSS can be seen by entering appropriate data into Cat Design Pro.

C-15, C-16, C13, C15 heavy duty engines (Provided sufficient torque is available – see recommendation below)


Caterpillar recommends that the engine have at least 1650 lb-ft of torque available for GFRS Caterpillar recommends that the engine have at least 1750 lb-ft of torque available for GFRSS


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