Swap out the 4-speed gearbox from a 4 speed ’73 240Z to a 5-speed ’83 280ZX non-turbo.
If you are running the 3.9 R200 differential you will want to pair it up with a gearbox that is designed to work with the lower diff gears. The ’81 -’83 280ZX non-turbo gearbox was built to work with the 3.9. This match will prevent any abnormal RPM and speedometer problems. Be sure it is a non-turbo, because the turbo based gearbox is meant to be paired with a 3.545 R200 differential. Go to the Transmission Calculator page and adjust for a RPM to MPH comparison.
Components for my particular swap:
- ’81-83 280ZX 5-speed
- ’81-83 280ZX 3.9 R200
- 215/45/17 tire size
If you compare the difference between the 4th gear on the 4-speed and the 5th gear on the 5-speed there is a RPM reduction at a highway speed resulting in a more comfortable rev range.
To make the swap all you need is a ’81-83 280ZX non-turbo gear box. It is a direct replacement for your 4 speed. The earlier 5-speeds are not the right length and would need to have the opening cut for the shift lever. This is NOT the case for the ’81-83 5-speed. NO cutting is required.
Remove the 4-speed and transfer the clutch fork, throw-out bearing, and insulator mount to the 5-speed. The mount bracket that bolts the gearbox to the car is a perfect match as well. I used a short-shifter that was made for the 4-speed, so I had to modify the mounting tabs with a grinder on the 5-speed. This was the only mod I had to make. Also, there is no need to worry about a speedo gear change as long as you are pairing it up with a 3.9 R200. The 5-speed uses the white gear where the 4-speed uses the yellow one, in case your wondering. A photo is worth a thousand words, so check them out…