T-18

If your J truck has a four speed, chances are that it is a T-18. The T-18 is a heavy duty cast iron four speed with unsynchronized first gear.

The T-18A has an unsynchronized Granny low first gear with a ratio of 6.32.

The T-19 can be a direct swap (depending on the origin) for the T-18/A with the important difference of a synchronized Granny 1st.

  • It is identified by the casting number of T-18 or 13-01.
  • The input shaft measures 1 1/8" and has 10 splines.
  • The output shaft measures 1 3/8" and has 6 splines.

T-18 Gear Ratios

1ST 2ND 3RD 4TH REV
4.03 2.42 1.41 1.00 2.97

T-18A Gear Ratios

1ST 2ND 3RD 4TH REV
6.32 3.09 1.69 1.00 7.44
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