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5-speed education


Iowa Mark

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I decided to go to the local pull-a-part looking for what was available as far as drive train swaps into my '76 shortbox 620, with it's L20b and 4-speed transmission. Mostly I'm looking for a 5-speed that will work well with the L20b, but may be asked to mate with a KA some day. Here are my choices. '96 shortbox hardbody 2 wheel drive with 186,000 miles. '84 extracab 4 wheel drive 720 with 203,000 miles. '82 280 Z with 98,000 miles and about a million wasps protecting it. All of them have engines still bolted to them and all of them show that the engines are bad and the trans are good. Well, maybe. I've slogged through the various searches on swapping things in 620s and still need an education on what works best. My gut says pull the Z apart and bolt it right up, but am I screwing myself in the future for a bigger engine? How do the gearing of the different set-ups work compared to the 4-speed I currently own? What should I pull along with the trans to make the swap easier? Starter, flywheel, throw-out, driveshaft, crossmember? I'm still very new to doing anything but maintanence and driving a Datsun. Thanks.

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I am not familiar with the KA engine, but I think it sits "straight up" and the L-engines sit at an angle.

I do know that when I put a 5 speed in my 521, I chose a transmission witha 3.321 first gear, I was using my truck to pull a trailer, and needed the low gearing. If you rarely load your truck down, a close ratio 5-speed would not be as big of a deal.

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Get the '82 280zx 5 speed. (as long as it's NOT a turbo) Pull the 4x4 720 tranny (it's no good for you no matter what engine you use because it has no speedometer drive in the tail stock anyway) and separate the front case half and keep it too.

 

If you decide on a KA later, swap the 720 front case half onto the 280zx tranny and you are good to go. If they won't let you have the case half just keep your eyes open for a bad Z series tranny.

 

 

The gears on the '82 are closer together so just a slight amount of extra effort is needed on take off as first is a bit 'taller' than the 4 spd you now have. This shouldn't be a problem for a truck with 4.375 gears but could be if hauling a heavy load. 5th gear is very high compared to a truck 5 speed but again the lower rear end gears will compensate. You should never climb hills, tow or carry a load or pass on the highway in 5th anyway... use 4th. for this.

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unless you plan on swapping bellhousings an l series trans wont work with a ka if you do a ka swap why not just use the ka trans that typicly comes attatched to the motor

 

The 240sx tranny is 3-4", the D-21 is still about 1 1/2" longer so the drive shaft would need to be shortened.

 

The 280zx 5 speed will fit the KA if a Z series front case is swapped on. This keeps the drive shaft.

 

The KA tranny is stronger.

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The KA tranny is stronger but the 240sx tranny is 3-4", the D-21 is still about 1 1/2" longer so the drive shaft would need to be shortened.

 

The 280zx 5 speed will fit the KA if a Z series front case is swapped on. This keeps the drive shaft.

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I can already see a very bad trend setting in. Pull the Z tranny and the 720 tranny. Store the 720 away for later, and go back for the hardbody engine and tranny, because it is very complete. That will become the spares on a KA conversion (oil pan, manifolds, wiring harness, blah, blah, blah.....) Look for a running KA. I already have a barn full of VW parts that started just like this. I should have taken up stamp collecting instead of lying on my back getting greasy. Thanks guys, I will head back for the Z-gutting next week-end.

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Grab the 280zx 5 speed. It will fit perfectly and do for now.

 

ONE:

You don't need the whole NAPS Z series 5speed just the front case half. Just wait and keep eyes open for a broken or scrap one and get it cheap. You're in no hurry, one will come around. Any '81-'86 720 or '80-'83 200sx 5 speed will work. This will allow you to keep the 280zx tranny with the KA and avoid shortening the drive shaft.

 

 

TWO

But why bother. The KA comes with a better tranny, you just have to shorten the drive shaft.

 

You decide which is cheaper or easier.

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Thanks, Mike. I'm going to go ahead and get the Z tranny and sit on it for a bit. The truck is still in the process of getting reassembled and painted. This was just going to be a run-around, haul stuff truck when I bought it. Unfortunatly I can't leave anything alone, and I remember my first 620 with the 4-speed. The second one had a 5 and was so much nicer on the highway. And, of course, this place has a knack of adding to the possabilities of mess'in with stuff.

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youve probably posted the markings... just 1 more time :unsure:

 

 

i need to determine what ZX 5spd i have already...

 

The external markings won't tell you what gear ratios are inside. All you can tell is the general age- whether it's an early trans or a later one. There are various ratios for each though.

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Here are links to Nissan Transmission drawings (not all inclusive, but may help)

Nissan Transmission Parts illustration - Drawings

http://www.drivetrain.com/parts_catalog/manual_transmission_overhaul_kits/nissan_manual_transmission_illustration.html

 

Drivetrain Information for many vehicles

http://www.drivetrain.com/

 

 

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X 2 on that Doug.

 

http://www.drivetrai...lustration.html .... wow......just wow. I can only hope the car model and years and kits match up, but the tranny description and name is...... wow.

 

 

 

FS5W71A was a Roadster tranny.

 

IIRC the 240Z could be fitted with a non U.S. FS5C71A Roadster competition 5 spd. with an L bell. The 260 could befitted with a non U.S. FS5C71B. These may have been a dealer installed thing other wise the 240/260/280z/zx came with an F4W71A through Sept '71 and FS4W71B from then through '79. The FS5W71B 5speed option was available from Aug. '76.

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Don't mean to hijack the thread but had a quick question about a 620 5 speed since you guys are on the subject. To swap the 620 5 speed into a 70' 521, is it just a matter of shorting the transmission mount 2in. getting the drive shaft shorten, and thats it right? I also understand that it is going to move the shifter 2in. back. It is going to mate with a L16 by the way. Is their anything I should know about as far as the T.O bearing or clutch?

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Don't mean to hijack the thread but had a quick question about a 620 5 speed since you guys are on the subject. To swap the 620 5 speed into a 70' 521, is it just a matter of shorting the transmission mount 2in. getting the drive shaft shorten, and thats it right? I also understand that it is going to move the shifter 2in. back. It is going to mate with a L16 by the way. Is their anything I should know about as far as the T.O bearing or clutch?

 

Yes, the drive shaft spline that is on the 521, bolts to the stock 4speed transmission. The 5spd doesn't have this, so the hole in the center of the spline will leak oil. This can be sealed with a 40mm freeze plug. Then the shortende drive shaft can be bolted back on.

 

521flangeonnonflangeF4W63needsplug.jpg

 

 

 

 

Y'all keep saying "get the '82 280ZX 5-speed." Are the ratios different in the '81 and '83?

 

It depends on what you want out of your transmission.

 

WIDE RATIO (this is a relative term and only used when compared to a different transmission gearing)

 

Some have a lower (high numerically) first gear. This means the next two gears have to be widely spaced between first and forth which is always one to one or straight through. This wide spacing of the gears makes this a wide ratio tranny. A low first gear is good for added torque on take-offs for a heavy truck or goon that may be used for carrying a load or for stop and go driving in town. It is also a bonus on a turbo car as it revs faster to boost. A draw back to a low first gear/wide ratio tranny is there is a bigger drop in RPMs when up shifting. This is a big disadvantage when racing as a motor can drop out of the useful power producing range. Here are the ratios for the '77&'78 620 and the '77- 79 280z. We'll consider them as a wide ratio compared to the later 280zx ratios.

 

1st.... 3.321

2nd... 2.077

3rd... 1.308

4th... 1.000

5th... 0.864

 

There are even wider ratio truck transmissions with 3.592 first gears and wider spaced 2nd 3rd gears!

 

 

CLOSE RATIO (again a relative term that only applies when compared to the above tranny)

 

A transmission with a lower numerical first gear means there is less space to fill between it and forth gear so the gears and the shifts are closer together. The lower the number the harder it is to take-off in first, (great for racing where there are few stops not so good in city driving) but once moving there is much less RPM drop between shifts. (again great for racing) Here are the ratios for the '80 and the '81-'83 280zx 5 speeds. Both have the same ratios, only the over drive is different.

 

1st.... 3.062

2nd... 1.858

3rd... 1.308

4th... 1.000

5th... 0.773 for the '80 and 0.745 for the '81-'83

 

There are even closer ratio trannys for competition with 1.858 first gears! This is the same as taking off in second gear in the above 280zx tranny!

 

Note that the '80 and on 280zx has a monster over drive ratio that may be 'too tall' and drop the freeway RPMs too low for a stock L16 to maintain efficiently. The 280zx tranny is for a six cylinder motor with lots of torque so it may or may not be ideal for a smaller output motor.

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