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Whats up ratsun ,Noob with a question.


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I was looking around the forum but I just can't find an answer. I have a 75 620 with a 4-speed, and I want to swap that out with a 5-speed. What tranny's are compatible with the L20b engine? I've heard zx tranny's, but out of what year? Is there any fab or cutting I have to do to fit this? Any help would be appReciated. Thanks guys.

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The 71B 5 speed was introduced for the '77 model year (as an option) on the 620 truck and the 280z and on the later '79 810. It was continued on into the 720 truck for the one year... '80, the 280zx '79-'83 and from the 810 into the Maxima '81-'84.


There were 3 main gear ratio choices, a wide, mid and close ratio gear sets.


Wide Ratio found in the '79 620 and '80 720 trucks

1st... 3.592

2nd. 2.246

3rd... 1.415

4th... 1.000

5th... 0.882 .... favors a truck with heavy load or car with 4 cylinder motor and low ratio rear end gears.



Mid Ratio found in earlier 620 trucks, 280z and first year '79 280zx, 810/Maxima.

1st... 3.321

2nd.. 2.077

3rd... 1.308

4th... 1.000

5th... 0.864.... favors light truck or car with 4 cylinder motor



Close Ratio found on all '80-'83 non turbo 280zx.

1st... 3.062

2nd.. 1.858

3rd... 1.308

4th... 1.000

5th... 0.773... favors 6 cylinder motor or 4 cylinder motor with high rear end gear ratios.


All the above will fit and work in your 620 with only the speedometer pinion from your truck needing to be swapped into the 5 speed to keep your speedometer accurate. Be sure to keep and use your clutch release bearing collar or housing but replace the bearing on it.








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...and yes we do chew up noobs on occasion.


The stock Hitachi carb isn't crap any more than any other carb that may be worn out or just out of adjustment. What makes you say crappy? Poor running can be many things. If you haven't... check your valve lash when the motor is hot. Poor clearance will cause poor idle and performance. You have a points distributor so when were they checked, gaped or replaced last? If you don't know it's time to find out. While there check the rotor and the cap. What do the plugs look like? This is a good indicator of engine condition and can also point to carb problems.


Sometimes carbs can simply be fixed/adjusted to clear them up. Replacement is best with another Hitachi as everything connects properly to it. The problem here is new ones are expensive and used ones likely have problems too. If replacing it consider a new direct replacement weber from Redline carbs. For about $300 it is a kit that allows you to convert over and has everything needed. The weber is simpler and more performance orientated.

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