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1975 280Z 2+2 4 speed
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Discussion Starter · #1 ·
I've had my 75 280Z out on some long drives, and one thing that is a real 'Pain' is the mismatched 4 speed trans. You run out of transmission long before you run out of engine, so what's involved in swapping my 4 speed out for a slightly more modern 5 speed ? What year 5 speed will fit, ( I assume a 1977 or 78 ) would be the least less complicated ? The rear transmission mount need to be changed and does the clutch linkage is the same and the shifter in inside the 5 speed transmission. Is there anything I've missed ?

Thank you, for your advice. :whistle:
 

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If you want a tall gear to have good low rpm high speeds stick with a later zx transmission. It has a .75 OD which gets you 80mph at 3k rpm. it also has a lockout provision for reverse. Its a bit taller in 1st gear (3.0 vs 3.3 or about that) so starting off may take more clutch, but it never bothered me. IF you have a lot of hills and get stuck in traffic it may be an issue. This all assumes you keep the 3.54 diff. Lots of folks go with a 3.9 for more peppy performance, but kinda defeats the purpose if you are complaining about running out of gears. The 3.9 just give you more gear ratios to choose from, keeping the engine in the power band for performance driving. I have the 3.54 with mine and find it useful on the open road when I want to go more than 70 for extended times. Its not much good below that as the engine will bog (70 is about 2.6k rpm so even then if you hit a hill you will need to down shift to 4th).

the zx trans will have the shifter forward about 1" maybe a bit more. You will need to rebend the shifter to get it centered in the rubber boot. Otherwise it end up with a shift knob too close to the front console.

You should use the zx shifter, it has a design that incorporates a moving pivot point allowing for better engagement. it is shorter and also needs a lot more bending to work. You will need to add an extension by the time you have it bent, or else deal with a VERY short shifter. You can use the Z shifter but you will need to notch it to get full engagement of some of the gears.
 

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1975 280Z 2+2 4 speed
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189 Posts
Discussion Starter · #3 ·
If you want a tall gear to have good low rpm high speeds stick with a later zx transmission. It has a .75 OD which gets you 80mph at 3k rpm. it also has a lockout provision for reverse. Its a bit taller in 1st gear (3.0 vs 3.3 or about that) so starting off may take more clutch, but it never bothered me. IF you have a lot of hills and get stuck in traffic it may be an issue. This all assumes you keep the 3.54 diff. Lots of folks go with a 3.9 for more peppy performance, but kinda defeats the purpose if you are complaining about running out of gears. The 3.9 just give you more gear ratios to choose from, keeping the engine in the power band for performance driving. I have the 3.54 with mine and find it useful on the open road when I want to go more than 70 for extended times. Its not much good below that as the engine will bog (70 is about 2.6k rpm so even then if you hit a hill you will need to down shift to 4th).

the zx trans will have the shifter forward about 1" maybe a bit more. You will need to rebend the shifter to get it centered in the rubber boot. Otherwise it end up with a shift knob too close to the front console.

You should use the zx shifter, it has a design that incorporates a moving pivot point allowing for better engagement. it is shorter and also needs a lot more bending to work. You will need to add an extension by the time you have it bent, or else deal with a VERY short shifter. You can use the Z shifter but you will need to notch it to get full engagement of some of the gears.
Hi Dave, I was looking for the same ratio of the 4 speed I have, but a better mix of gears that would make my 47 year old Z a little better in both traffic and on the highway. Once I'm in 4th gear, the car feels like it's waiting for the next higher gear, but there is none. I have been searching forum posts and found on breaking down the different transmissions and I'm not sure, but it seems the : FS5W71B trans. fits my 75 and gives a little better top end ? What do you think ?
 

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the early 5 speeds more closely match what you have, but the OD is only something like .87 IIRC. Thats not much of a overdrive. the later 5 speeds from the ZX like mentioned are the more popular option. With a .87 OD its not going to give you much more that what you have. I presume the .75 was later used in the ZX for a reason.
 

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the ZX trans works in the Z with no mods needed the splines on the output are the same, the length is approx the same (I did not measure it but its not a problem). The drive shaft (prop shaft from trans to diff) I "think" has a different flange on the back that mounts to the diff, so changing diffs may require dealing with that. On mine I just pulled the trans, and reused all the clutch stuff (the throw out bearing and same flywheel, I did NOT up the clutch size to match the ZX), and modded a ZX shifter (its too straight, need an S bend to position correctly in the boot, and added an extension). The orig shifter will limit full engagement of some gears as the throw is limited, I presume due to the length of the ears where the pivot installs. I have some videos on my channel, just look for ZX transmission. I go over a lot of this stuff.
 

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1975 280Z 2+2 4 speed
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Discussion Starter · #7 ·
Ok, Can you show or tell me where the serial number or model # FS5W71B is located on any transmission I go to look at ? If I don't know I'm likely could buy the wrong transmission ? :unsure:


Thank You,
 

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do you want the wide ratio (Z) or the narrow ratio (ZX) transmission?
wide has no lockout provision narrow has the lockout. the lockout is on the left hand side (other side from reverse switch), looks like a diamond plate bolted on with 2 nuts.

Z is OD .87 5th gear.
ZX is OD .75 5th gear.

if you want to know what it looks like just google images, should find plenty. there are NO model numbers on the transmissions. there are clues like how many exhaust hangers on the tail shaft housing, and how long the ears are on the shift pivots. The main thing is the lockout to determine what you have.
 

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1975 280Z 2+2 4 speed
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189 Posts
Discussion Starter · #9 ·
do you want the wide ratio (Z) or the narrow ratio (ZX) transmission?
wide has no lockout provision narrow has the lockout. the lockout is on the left hand side (other side from reverse switch), looks like a diamond plate bolted on with 2 nuts.

Z is OD .87 5th gear.
ZX is OD .75 5th gear.

if you want to know what it looks like just google images, should find plenty. there are NO model numbers on the transmissions. there are clues like how many exhaust hangers on the tail shaft housing, and how long the ears are on the shift pivots. The main thing is the lockout to determine what you have.
I think I want to go with the wide ratio Z transmission. So what can I look at to determine it's a wide ratio 5 speed, or have you covered it already ? I never dealt with changing transmissions on a 280Z ? :unsure:
 

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I put a ZX 5 speed in my 75, nice for highway cruising.

One problem I had was the shifter hitting the center console on forward shifts. Had to bend the shift lever quite a bit.

Was fine without the console, but when I put the console back in 3rd and 5th would not engage. I don't know if you can just use the 4 spd shifter. Would have to compare and mine was already gone.
 
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