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Guest jdllaugh

280z 4 speed to 5 speed swap

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Guest jdllaugh

This has probably been discussed before, but I couldn't find answers in a quick search. I'm looking at buying a 280z 4 speed car. Would swapping in a 5-speed be a direct bolt on, or would the drive shaft have to be changed. Any other considerations? I'm talking a 5 speed from an L6 car.

 

Also, anyone driving a 4 speed 280? How does it do on the highway? Does it cruise at a reasonable rpm?

 

James

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There are actually three different 5-spds for the 280Z/ZX. The 1976-1979 has the same first four as the 4-spd. and a fifth of about .86:1. The '80 is the oddball with different 1st & 2nd plus a .777:1 5th. The '81-83ZX has the same 1st & nd as the '80, the same 3rd & 4th as the 76-79 and a .745:1 5th. Combined with the 3.90:1 differential it has the best overall performance.

That being said - If you are going to put in a five speed for general use and good cruising - use a combination 5-spd and differential out of an '81-83ZX. If you don't care a lot about cruising but want accelleration and OK cruising get the early model 5-spd and still use the 3.90 R200.

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Hi, Funny you should ask about the trans swap! I just put an '81 zx 5-speed into my '78 280 yesterday (man I'm sore, pulled the trans from the u-pull it and bought it for $100 , carried it to my Z [my only car]. drove to the base skills center, put her on jackstands, pulled the 4-speed full of fluid because BOTH the fill and drain plugs stripped out DOH! , held the 4-speed up for about 10 min. and let it drain into a pan..., replaced my clutch, and manhandled the 5-speed in, all in about 8 hours, including 2 hrs of driving time to get the trans., and get back to base.) Not too shabby for a 5'6" dude that dosen't weigh much more than the friggin' trans. (I weigh 155lb soakin' wet) Did I mention I had to do this all myself, one dude helped by lowering the jack when I removed the 4-speed, but that was it!

I also used nuthin' but hand tools, and a floor jack, one of which was a CHEAP 3.95 ratchet..it's broke now but it worked while it had to, which was tight. Talk about fixin a car old school style.

The transmissions are the same length, about the same weight, and use the same clutch, input shaft, and output shaft. Just be wary of getting a 2+2 flywheel because they had the bigger clutch, but as long as you use your flywheel any 240-260-280z and 280zx trans will bolt up.

BTW I'm very happy with this trans, despite it's being noisy (the donor car had 250,000 miles!! but it was the best they had, and it works for now..it wuz only a hundred bucks.)

The reason? The .745OD that was mentioned. I have a 3.54 R-200 and decided (for now) to keep that gearing, as I feel that the stock powerband of the L-28 (low compression) will benefit from the taller gearing for most driving (the 4-speed did nothing but spin in 1st in a drag start) so i changed my speedo pinion (took the one from the 4-speed and used the zx sleeve as they are different)...here's the results.

 

4-SPEED (all are as indicated, but speedo is dead-nutz at 60mph)

1st gear range 0-25mph

2nd gear range 0!-50mph

3rd gear range 1-90mph

4th gear range 5-125mph (those L-series are TORQUEY with stock cams!)

Rpm@ (in 4th gear)

10mph---800

20mph---1100

30mph---1500

40mph---2000

50mph---2400

60mph---3000 (pwr range stock cam 500-4500rpm)

70mph---3500

80mph---3800

90mph---4100

100mph---4500

110mph---4800

120mph---5100(and she's not revvin much more than that !)

 

5-SPEED from 1981 na 280zx, used with 3.54 rear (yes speedo is still accurate, verified it AND I used my speedo gear from the 4-speed)

range, mph (max engine speed 5500rpm)

 

1st gear---0-50! mph

2nd gear--5-75mph

3rd gear--5-100mph

4th gear--5-125mph(@5200rpm, not enough power to rev higher)

5th gear--25-??? (assuming enough power possibly close to 200mph!)

 

MPH@RPM in 5th gear

30mph---1000

40mph---1200

50mph---1500

60mph---1900

70mph---2300

80mph---2700

90mph---3000

100mph--3300! overdrives are great!

 

As you can see the gear spacing is much closer in the ZX trans and the 5th gear is GREAT for cruising...I can't even hear the engine anymore, and can now keep up with SoCal traffic without seeing dollar bills go out the tailpipe (gas mileage was 19mpg before, i haven't measured it yet but I'm sure I'm mid 20's now!)

Good luck with your conversion, Z's forever!

Bryan

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Guest jdllaugh

Wow! Thanks for all the info. Very useful. I've never had to drop a tranny by myself, but I did pull the differential for my 4-wheel drive s10 not too long ago, by myself. Probably only weighed 70-80 lbs, but try holding a weight like that steady about 5 inches above your face, while laying on your back, as you slip it onto a splined shaft! Lots o fun!

 

James

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Phantom,

If I get a t-56 that would be awesome especially being that it would probably have an LS-1 in front of it! One (minor) correction to your statement: yes .50:1 OD on 1994 and up T-56 transmissions. 1993 and earlier F-body T-56 had a still-awesome .63:1 overdrive. This info came from the JTR swap manual, fifth revision. (they recommend using a '94 up T-56 for thier V-8 swaps. ) The SIXTH revision probably will recommend using the '98 up trannies because they had the nifty, slick hydraulic throw-out bearing that allows installation w/o hammering the trans tunnel.

I would still love to have a T-56 behind the L-28 but would definitely have to go (a lot) lower on the ol' gearing in the diff. (I can still pull hills w/o downshifting but when you drop the hammer not much happens w/o a downshift.....the ONLY downside to the neat little thrill of watching the speedo wind to the right while the tach needle seemingly stands still!) Hey, that's what a stick is for, right? SHIFTING!! No prob there! I still don't think the L-28 could pull a .50:1 OD without some SERIOUS work.

O.D.'s are so neat, IMO because of that....the higher the RPM, the more RPM drop(compared to a 1:1 ratio) you'll see with an O.D.---as my lil' previous post shows. My guess to this is because the OD can be expressed as a percentage....so using a set # like .75:1....75% of any given RPM, or a 25% RPM drop from 1:1...so 25% of 6,000 rpm is going to be a lot more than, say 25% of 3,000RPM. (I guess that's why at low speeds the rpm in 5th in my Z is not much lower @20mph than with the 4-speed in 4th...but at 100mph...LOOK OUT! :lol: )

 

To Jdllaugh,

Thanks for the thank-you, but the TRUE thanks goes to all the wonderful people here at Hybridz.org who's posts and generosity of information taught me just about everything I know about Z's. YOU GUYS ROCK!

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twoeightythreez,

 

I am interested in doing this exact same thing with my '77 280Z. As I understand it the 280ZX model 5-speeds have slightly different wiring for the reverse lights, did you find this to be the case? Also, apparently there are some parts you still need from the 5-speed that can't be used from the 4-speed, a cable or some such thing. Anyone?

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On 5/14/2019 at 11:40 PM, el_pende_hoe said:

What if you wanted to swap out a 5- speed tranny for a 4- speed? Are there any perks?

The only advantage I can think of is 4 spds are much cheaper than 5 spds and you could sell the 5 and make a few bucks.  4 th gear in both are 1:1,  5 th gear is better for gas mileage on the highway.

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Or if your 5-speed was scrap and a 4-speed was all that was available. ...or someone is lazy and wants to shift less?

 

But if you want to do it, you follow the same procedure...  I would check out the gear ratios of each transmission on xenon (I think that's right).

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