[GMARTING]

I have 240Z with a 5 speed in it but I don't know what year the transmission came from. Does anybody know if you can find out the year of manufacture based on the serial number that's stamped on it? Thanks for your help.

 

[240ZIP]

Five speed trannys from 280's came with two fifth gear ratios: .86 and .78. The former gives you a 15% overdrive, while the latter will reduce your cruise revs by nearly 25%. The gear ratios of the various Z transmissions are as follows: 280 Turbo trans: 1st: 3.5; 2nd: 2.144; 3rd: 1.357; 4th: 1.0; 5th: 0.78. Early NA 5 speed (before 1979) 1st: 3.321; 2nd: 2.077; 3rd: 1.308; 4th: 1.0; 5th: 0.864. Late NA 5 speed ('79 to '83): 1st: 3.321; 2nd: 2.144; 3rd: better; 4th: 1.0; 5th: 0.78.

Given information about the tire size, RPM, rear differential, and speed of the car, you could determine the 5th gear ratio and thus the transmission type.

 

[GMARTING]

Thanks for the help. Do you know what the formula is for plugging in all of this various info?