Gear ratios can help define the performance and drivability of your Datsun Z, whether it's a 240Z, 260Z, 280Z, or 280ZX. The right gear ratios also help customize the car's acceleration and top speed to match your driving style. Some of these ratios can bring out your Z's full potential.
The perfect gear ratio setup can change your entire driving experience by improving engine power and improving fuel efficiency.
Get ready to unlock your Z's true capabilities. These can meet your racing needs and when you want to cruise or have your restoration goals. Let's get started!
Table of Contents
What Is FS5C71B Transmission?
The FS5C71B transmission in the Datsun Z cars came in two different versions during the original production, and each version fits into different driving styles. Enthusiasts still argue about which option might work best for their individual needs.
Your 1977 to 1980 Datsun Z car came with a wide-ratio transmission. Its spread-out gear spacing gave you some smooth power delivery and relaxed highway cruising. Z car owners can sometimes love how comfortable this version might feel during their drives.
From 1981 through 1983, Datsun switched over to the close-ratio transmission - this version kept your engine RPMs tighter between gear changes. A local Z car owner recently took his close-ratio 280ZX out to the track and said how much the transmission kept his engine right in the power band through every single turn.
The tail housing helps you tell which transmission you might have. The wide-ratio drops your RPMs more between gears, while the close-ratio ensures steadier engine speeds during those changes.
Track day enthusiasts usually like the close-ratio transmission because it can help with momentum through technical sections. Other drivers sometimes choose the wide-ratio because it adjusts better to more road situations.
Your FS5C71B transmission works with as much as 300 wheel horsepower. These units earned their tough reputation in racing and street use. Some Z cars still run their factory transmissions even after more than 40 years on the road.
The wide-ratio's fifth gear delivers some peaceful cruising on longer highway trips. That helps you save some fuel and cut back on engine noise.
The close-ratio trades away some highway comfort to deliver fast acceleration and better performance on the track. Race drivers can maximize the close-ratio's tighter gear spacing. Your engine stays closer to peak power through corners and straightaways. That setup lets higher average speeds out around the track.
Why Pick Close Ratio?
Close-ratio transmissions will keep your Datsun Z's engine running at its best. You'll find these more often. You can also see smaller gaps between the gears, too - that means you won't lose as much power to the gears when changing them.
Race enthusiasts love close-ratio setups in their track-focused Z cars because the engine stays right where it needs to be at peak power. Your car will also respond faster and accelerate quicker when you're pushing it hard on the track. A close-ratio setup means you'll also need to change gears more often, though.
Long highway drives might wear you out since you'll always be hunting for the right gear to use during normal cruising.
If you love track days, then you'll like how close-ratio gearing keeps steady power flowing while you're pushing your Z to its limits. Your own driving style and personal preferences should help lead your transmission choice. The final drive ratio needs to match your transmission setup well. These two big parts work together like dance partners. If one is out of step, your car won't deliver the acceleration or the peak speed that you're looking for.
Z car owners who hit the track say close-ratio setups completely change how their driving feels. The RPMs stay higher between changes, so you can keep momentum through hard sections. You might even knock some time off your lap records during those track days.
Close-ratio transmissions make every drive feel a bit more fun and focused, too. Your engine will stay in its power band longer, and it lets you sing that sweet inline-six song. Each gear change feels more purposeful and connected - and this turns every drive into a better adventure.
FS5C71A Numbers And Purpose
The FS5C71A transmission played a big part in the Datsun Z's long history, even though Datsun had first made it for the Roadster 2000. They later tweaked it and adapted it to work well in the Z car.
You'll find this transmission in the earliest 240Z models straight from the factory. Datsun needed to make some changes to get it to work just right. They added a different clutch housing and changed the gears for better performance on the road.
Z car enthusiasts still argue about how well the FS5C71A actually performs. People started calling it the "long tail" FS5C71A because of its extended and stretched-out main shaft and tail casing. These changes helped the transmission to manage the power that the Z car could throw at it.
They like how it feels on the road - especially when they're carving through twisty and winding back roads. Others like newer transmissions that can give you some different gear ratios to match their driving styles.
Original FS5C71A parts are tough to find lately. The two-piece bell housing is especially hard to track down. Z car owners now have to search for some restored units to make their cars more period-correct.
European Z cars ran with the FS5C71A until January 1972. After that point, Datsun rolled out the FS5C71B transmission instead. This newer version came with an easier single-piece bell housing and had different gear ratios to make the car perform better.
Race enthusiasts sometimes tell you about the FS5C71A's gear ratios. The transmission actually came in three ratio configurations. Each of these setups worked best for different types of driving and racing situations. Street drivers often chose the wider ratios that made driving more fun.
F4W71A For Everyday Driving
The F4W71A transmission in classic Datsun Z cars has a smooth four-speed manual experience that connects you to the car. You'll find that this easy gearbox just does its job reliably without any tough features in the way. Your hand will naturally rest on the raised shifter position with the three-piece case design.
This transmission feels very mechanical and weighs less than the five-speed models that came later. You'll feel like you're transported back to a big age of Japanese sports cars as you run through the gears.
Your first gear ratio of 3.549 helps you jump off the line faster. Then you'll drop into second at 2.197 and third at 1.420. Fourth gear's 1:1 ratio works for lots of driving situations. The gear ratios match up well for fun drives on some winding roads or around town.
Highway driving shows where this transmission is starting to show lots of age. Since there's no overdrive gear, your engine will run at slightly higher RPMs on the highway than modern cars do. That means you'll use more gas and hear more engine noise during longer road trips.
The F4W71A works so well as you carve through back roads and change between second and third gear. You'll get feedback in the mover during aggressive driving. These transmissions are reliable enough that you can still like the drive without worrying too much about damage.
It's a good choice for canyon runs and autocross events where quick changes mean more than highway efficiency. Z car fans often hunt down these early four-speeds because they bring you a pure driving experience.
Which Differential Fits Best?
Your choice between some Z-car differentials doesn't need to stress you out. You'll find three main options for your Datsun Z - the classic R180, the tough R200, and the rare R190. Each one can help to add something to your build.
The R180 differential is in pretty much every 240Z that rolled off of the factory line. This lighter option works if you're keeping the items stock or doing mild power upgrades. Z owners also love how it just bolts right in without any trouble, too.
The R200 differential works when you're pushing serious power through your Z. It's built much stronger and harder than the R180, though you'll feel some of that extra weight. You'll probably need to modify the stub axles and other parts to make it fit. Still - that extra work can pay off if you're building something wilder.
To find an R190 differential is like trying to find a sea unicorn - these mostly showed up in race cars and models. You get the best of worlds here - it drops right in like an R180 but works with more power, too. The only real challenge is that finding limited-slip options for these can feel pretty tough.
Your gear ratio choice can affect how your Z feels when it's on the road. A 4.11 ratio will light up your day for track events. More of a highway cruiser? You might love how a 3.54 or 3.90 brings those RPMs down at speed.
Remember, though, that your transmission setup can help determine how these ratios work and actually feel. The R180 keeps your Z dancing through the corners just like it should. The R200 can add some weight out back - but that's added security if you're running big power. Lots of Z owners have learned this one after buying parts that looked right but didn't quite fit.
Limited slip options open up some new possibilities for your build. Most R200 setups use clutch-type LSDs from newer Z cars. With an R180, you also have more options from a few different makers.
Calculate Differential Ratios Clearly
Gear ratios work like riding your bicycle - the different gears affect how easy it is to pedal and how fast you can go while cruising along. Your car's differential gears work in the same way as well.
When you need to find out gear ratios, it's very easy. All you need to do is divide the number of ring gear teeth by the number of pinion gear teeth. Your Datsun Z may have a ring gear with 47 teeth and a pinion gear with 16 teeth. Do the basic math, and you'll end up with a 2.937 gear ratio.
Each ratio can give you a different kind of feel when you're driving. A lower ratio, around 3.90, will get you moving faster from a standstill - which is for zipping between stoplights. Keep in mind that your fuel economy will take a hit, and your engine will be working harder when you're on the highway.
Higher ratios like 2.937 are better for comfortable highway cruising. Your engine will stay smooth and calm at higher speeds. You'll save some money at the gas pump, too.
The stock 3.36 ratio works for most Datsun Z drivers.
Lower ratios around 3.70 or 3.90 are the preferred choice for turbo Z owners. These ratios make your turbo kick in quicker, which makes your car feel more fun when you drive it. The increased engine speed isn't a problem since turbo engines like to be at higher RPMs anyway.
Your transmission choice matters when picking the right ratio. A four-speed manual paired with a 4.11 ratio turns your Z into a lightning-fast street machine. A five-speed with a 3.36 ratio changes it into a great highway friend.
Build Your Dream Car
Your love for driving will shape the perfect balance of the transmission and the differential ratios. These big options can turn every drive into a fun experience, whether you want intense acceleration or more relaxed highway cruising.
You can choose between intense track days on the weekends, or you might just like some smooth drives. Classic Datsun Z cars are at their best and their brightest when their parts all work together well. Your goals and your driving style should lead your setup decisions.
The roads you drive on and your usual driving conditions will help point you to a good choice of ratio combination. A well-planned setup now means you can stay away from the issue of mismatched parts later on.
At Skillard, we share your passion for Z car perfection - down to the smallest detail. Your transmission and differential options are just the start of the car's transformation.
Our reliable and tough custom Datsun parts catalog has everything from aluminum door cards to aerodynamic spoilers. You'll find the performance and style upgrades your Z car deserves at Skillard.com. Our expertly designed parts can help make your dream car a reality!
