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Newbie questions, please help!


DrumCzar

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Hi, I'm new to this board, and I've got a few questions (sorry if this is long!). I ran a couple of searches and found a few answers so far, but now I'd like to know: I have a '73 240z that needs a new clutch, I'd like to have a 5 speed tranny for better fuel economy, and I have a parts 280z. Is it worth attemting to swap? I know the 4 speed in the 240z is fine, but I'm not sure how the 280's 5 speed is, and my car is at the trans. shop now waiting for my decision. If you need more info please let me know! I guess what I'm asking is if it's even worth bothering changing the tranny (I've heard that the ZX trans. were the first 'real' 5 speeds), and what would be invloved, i.e. is this a direct swap, or will I need special parts, etc? Thanks so much, I look forward to learning more about these awesome cars!

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The 5-speed transmission swap is a very popular modification to the early Z's. The transmission should bolt right into place, but, there are a few things to note:

- Use the throw-out bearing sleeve from the 5-speed.

- You will need to modify your center console SLIGHTLY because the 5-speed shifter is closer to the engine.

- You might need a shorter stick shift (unless you like the longer shifter). But, I'm not 100% sure about that one. Maybe someone else can back me up on this.

- Driveshaft.... I don't know about this one. But, someone should be able to let us know if you can use your stock driveshaft or not.

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I would go back with the 240.Then do your research on what is required and the pro's and con's of the 5 speed.While the 5 speed is out you would want to have it checked out, replace the front and rear seals,Check u joints,tranny mounts etc...If you have a tranny shop doing the custom console,custom tranny swap they will charge you big time for a job they really have no experence.If you make a hurried decision without doing the correct prep you'll most likely be back at the tranny shop.The kind and knowledgeable members of this web site can walk you through each step of the process when you are ready.You'll feel good 'cause you did it yourself and you will have done it correctly! Not to mention you'll have very little use for the tranny shop anymore as you'll be a do it yourself kinda guy! Have fun!! Daniel

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I installed a 280zx 5speed in my late 73 240z with no problems. the shifter fit fine and so did my driveshaft. I so believe you need the later throwout bearing or the clutch won't work correctly. Also use the speedometer drive gear from your 4speed to keep your gauge accurate. I don't remember what year trans I used. There are 3 different kinds not including the turbo, and I don't own that car anymore. Hope this helps. PS My gas mileage did not really change. Still got about 28mpg on the highway in either 4 or 5th gear. It was quieter though.

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Most people go for the 5 speed swap when they plan on changing the rear end ratio to something quite a bit lower than the stock 3:36. The fourth gear ratios of the 4 and 5 speeds are 1:1, and fifth is around .86:1 I believe. So, if you think you might want to go for the rear end swap in the future you might want to go ahead with the tranny swap now, if it's already apart you won't have to pull it later. The biggest benefit of swapping the 5 speed is with a lower rear gear you get quicker acceleration in the first 4 and have overdrive to cruise on the highway. It's isn't the most difficult swap so if you are so inclined go ahead and do it. But with the stock rear it is going to be a bit sluggish in fifth gear. Your final drive ratio would besomewhere between 2.90:1 and 3:10:1 in fifth ( I'm just guessing, I'd have to find the formula to figure it out exactly) so there is my 2 cents worth.

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When you do the tranny swap, use the throw out bearing and sleeve that matches the clutch assy that you are using, not the trans. That is what must match. The deck heights are somewhat different for the different cars and you must have the sleeve height match the clutch set or it won't work correctly.

I had a list of the different clutch deck heights around somewhere, but would have to look for it to be more specific.

Believe me taking the trans out for the third time to get it right is no fun at all....

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Correct me if I'm wrong here, but I think pauls240z has it wrong. You would want to keep the speedo drive gear for the transmission that you are putting into the car.

If you use the 4 spd gear on a 5 spd, that would give you a different ratio going to the speedometer.

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Let's see, no you would want the drive gear that came in the four speed since you want it to read right with a 3:36 rear. 280's had a 3:54 so if you put in the 280 drive gear it would be off. You want the drive gear that corresponds with the rear end ratio so that your speedometer would read according to the final drive ratio. Unless he had a 3:54 from an automatic which would make it right with the drive gear from the 280. I don't think I'm confused, or am I?

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Welcome DrumCzar,

Just wanted to make some clarifications. Okay, there is a lot of good information here but a few things to clear up. First I have no experience with the T-5 and so I am not going to cover that trany, it only came stock in late ZX turbos.

1) Physical differences- It is a bolt in swap to go from a '73 4-speed to a 280Z or 280ZX 5-speed, which are physically the same with different ratios. The problem with the console was only for the '70 or '71 240s that had the old clunky style gearbox, like mine had. From here I am only going to refering to the '72 - '76 4-speed trans. Starting in '72 the console and trans tunel design was changed by Datsun for the new design 4-speed with the shifter being more forward. This was used through the Z and 280ZX series cars in both 4-speeds and 5-speeds. I believe the 4-speed and 5-speed are slightly different in length but your shift boots, console, driveshaft, shifter, clutch slave cylinder, and shift fork will work. I don't remember for sure what I did about the throw out bearing and sleve but I believe it is correct when Dave mentioned it needs to match the clutch. So you should probably use what is from your 4-speed, unless you are putting in a later clutch. Also, you should replace the throw out bearing while the trans is out. Use the speedo gear from the 4-speed if you have the stock diff because it will keep your speedo correct, that is depending on how close your tires are to the stock size. The 280Z's and 280ZX's came with different diff ratios and will make your speedo off. There are a couple differnent speedo gear carriers and you may need to take the plastic gear off one and place it on the other, it is held on by a needle pin. The speedo gear is driven off the tail shaft of the trans so it doesn't make any difference that you are going from a 4-speed to a 5-speed.

2) Gear ratios- The 1st -3rd ratios are slightly different in a Z 5-speed compared to the 4-speed. There is a great tool on the web at http://www.geocities.com/z_design_studio/ which has information regarding different trans ratios and diff ratios. You can even mix a match and see the net result in speed@RPM and even see what different size tires will do for you. One note about this page is that they only list one 240 trans, which is the early clunky style. They list the later 240/260/280 style as a 260 4-speed. It also has all 3 (or 4) stock 5-Speeds and some Nismo competition 5-speeds.

Unless you have lots of money, since you are paying someone to do this type of work I would probably stay with the know good trans instead of taking a chance on the 5-speed.

I hope I didn't miss anything! Corrections, questions, and comments are always welcome!

Have fun!

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  • 4 weeks later...

First, you need to know that the 280Z came with a 5-speed. Depending on what you are going to do with the car. You need to decide if it is going to be used for gas milage or speed. For gas milage use the 280Z 5-speed. For speed go to the early 280ZX 5-speed. Also switch out the rearend to a 280ZX R200. You can go to a 3:52 or 3:90 gearing. For milage keep the stock gearing in it. Keep the throwout bearing and sleeve that comes with the transmission. Also get the drive shaft from a 280Z or 280ZX coupe that has a 5-speed in it. The 4-speed drive shaft is to long. Most every thing after that is a bolt in. About the speedo gearing, check out the following site for info on which gear you will need: Zdriver.com

Zcar.com

Zhome.com

HybridZ.org

Depending on mods you have on the car. They will tell you which color gear you will need for it to read correct. I had 15" tires and had to use the white gear. Good Luck, Rich.:)

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