The trans gear ratios and trans designations are independent of each other.

The use of the low gearset came about to allow use of a numerically lower rear axle ratio for fuel economy - used in either a 904/998/999.

The 904/998/999 designation came from relative torque capacity - the number of clutch discs and band widths used.

My recollection is the low gearset became available in 1980.

Last edited by Transman; 02/02/20 11:28 AM.