Five speed vs three speed

[Pichuki]

I own an 83 280zx 3 speed. I would like to do a five speed swap because I ejoy driving a manual car, I feel more ''connected'' with the car. The only thing that I'm afraid of is that my z will still ride at high rpms going down the highway. I travel 60 miles to work and back everday. My z at 70mph is at 3500 rpms.. A little to high for my taste. If I were to change over to a five speed, will the top end speed increase? Thus lowering my rpms ? Btw my car has stock tire size, not smaller diameter wheels. Any input will really be thankfull.

[78zcar_blue]

Hello,

I have a 78 with a five speed and it runs around 3K rpm's at 70 mph I am looking to put a 80 zx five speed from my parts car after a rebuilt into it, what would be best from the ratios I have talked over with a friend would be an 82 or 83 zx 5 speed, you can check out the various gear ratios for each in a shop amnual. Hopefully this is some help to you.

[SteveJ]

I own an 83 280zx 3 speed. I would like to do a five speed swap because I ejoy driving a manual car, I feel more ''connected'' with the car. The only thing that I'm afraid of is that my z will still ride at high rpms going down the highway. I travel 60 miles to work and back everday. My z at 70mph is at 3500 rpms.. A little to high for my taste. If I were to change over to a five speed, will the top end speed increase? Thus lowering my rpms ? Btw my car has stock tire size, not smaller diameter wheels. Any input will really be thankfull.

XenonS130 has a link with 5 speed transmission ratios. The 83 FSM, available at the same link, should have the ratios for your automatic.

[Pichuki]

Thanks SteveJ this what I found, it might help someone else like my self:Datsun/Nissan made several 4 and 5-speed manual transmissions available in the second generation Z car or S130. The 1981-1983 FS5W71B is a "close ratio" five speed transmission where the FS5R90A 5-speed transmission found in the 1983 280zx turbo is a "wide ratio" transmission. Close ratio transmissons are preferred for road racing as they allow the driver to maintain a tighter rev range between gears compared to wide ratio versions.

Finding the "optimum" transmission for your car all depends on what you are wanting from your car. For most people the "best" transmission is what is already in your car.

You can tell the difference between the FS5W71B and the FS5R90A by the shifter mounting.

[Pichuki]

Thanks 78zcar blue

[Bruce Palmer]

If I'm understanding the question it's all about the overdrive ratios. Later ZX 5 speeds are like 25% over drive where the earlier boxes are like 15%. so you'll get longer legs with the later box but your rear gears may be too low to pull the long overdrive. I run the long OD tranny in my wagon w/3.9s and a torquey 2300 so it pulls fine in combination.

Another benefit is that first is a longer legged gear set so is more useable.

[IdahoKidd]

Will the top end increase with an overdrive transmission, not noticeably. It will run lower rpms at the same speed, but essentially runs out of power to push it any faster. The zx 5 speed was made for the heavier zx 5 speed. It is also the easiest to find. You can get all the parts from the same donor car at a pic n pull or from a donor car. It is a project and will take some time and some experience, or some $$$ to have a shop do it. Net gain from an economic standpoint will be a loss. You will never be able to drive it far enough to make it pay for itself. But, if it is what you want, it doesn't matter what it costs........

[Racer_Z_]

The 5-speed has an "overdrive" gear. Most call it fifth gear. An overdive gear is any gear that is over 1:1, nothing more, nothing less. The 3-speed automatic and the 4-speed manual both have a high gear of 1:1.

So, yes, putting in a 5-speed will lower the engine RPM at highway speeds.

If it's still not low enough for you, you can change the differential gearing later. Not all 5-speeds have the same fifth gear ratio. I personally would not want a big fifth gear, but others do.

[tlorber]

Pay particular attention to your final drive (differential) ratio. Trannies and diffs are meant to be paired together.

I would imagine that in an automatic, you probably have something near a 3.5. Stock manual ZX's had a 3.9. So if you put in an '81-'83 five speed (which is THE period correct tranny for your car) your problem will NOT be running out of rpm's on the highway. If anything it will be too tall at the lower end. Not by a huge amount, but still something to consider.

[Z train]

Here is a good calculater.You have 3.54's with that automatic.Same as my 810 wagon.I'm transplanting a 620 5-speed and it'll be just what i ordered.As to the top end,you don't HAVE to use 5th gear on surface streets.

Ooops.....

http://www.wallaceracing.com/calcmph.php

Edited March 1, 2011 by Z train

[d240zx2]

My '70 had the stock 3.36 rear ratio. I plugged in the '82-'83 5 speed 'cause I love a CR tranny. The performance sucked in 5th gear. Popped in a R200 3.9 and boy, howdy! did that car come alive. Before the rear end swap, the best I could do in 5th was about 100, just wouldn't pull past it. Now, with the 3.9, I've seen 6700 on the tach in 5th and still climbing.

Point being, you've got to mate your tranny with the rear ratio to optimize your performance.

[Zs-ondabrain]

R200 3:90 diff

79' 280ZX 5-speed

225/50ZR16's

At 80mph, my tach is barely seeing 3000 RPM. Makes for Great Gas Milage on the freeway when doing 65 or 70 MPH. Like Frank says, It's all about mating the right Tranny with the right Rear-end.

Dave