zhome lied. Compare them in the FSM, but like I said, it's all rather moot.

I just did compare them in my 77 FSM...but they show the same ratios for the F4W71B and the FS5W71B

but whatever, no point dragging on a meaningless conversation like that.

Well, after looking in the FSM, I realized that all this time I was comparing an 81-83 5 speed, which is what I have in both my cars, to a 77-78 4 speed. I'll admit it, I was wro......

'ts ok. even the best of us could make a mistake, and admiting when you're wrong means you're a good person XD

I have a question that I don't really understand much though. I've heard that the early/late can be a close ratio and a wide ratio (not sure which is which) are they talking about the spacing between 2nd and 3rd?

m4xwellmurd3: this should help. if it doesn't come through as a link, just type it into your browser...

http://datsunzgarage.com/trans/

ah ok, now I see the difference. that explains why those years also got the 3.90 diff I suppose. (which is actually what I want to put into my Z)

So then, what would be the best option after all???

So then, what would be the best option after all???

I tend to agree with is said in that link:

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. I wouldn't lose sleep over which is the "optimum" trans for your car, for most people the "best" one is what you have in your car right now.

fwiw, i have the b version 5spd and am very happy with it. the 0.745 5th gear ratio is sweet for the highway. i turn 2900rpm at 70mph

(kidding here)...i'll stop everyone before it starts : let's not get into a 100+post-reply session about tire-wheel size/rear end ratios/5spd vs. 4spd vs. automatics vs. rpm,...and on and on and on...

I'll add another thing to consider: what cam are you using? The stock cam provides good torque down low but starts to decline by 4500 and is falling off pretty rapidly after 5500. If you were using that with the later 5 speed (81-83) and a 4.11 diff, I think you'd find that you would need to shift too soon. I think that a 3.54 diff and late 5 speed is an excellent combination with the stock cam. You might consider a 3.7, but you'll be upshifting at lower speeds than you currently do with the stock 4 speed.

You mentioned that you plan to swap to a 3.9 or 4.11 diff later, and with a cam where the power/torque peaks are higher up this is a very nice combination. In fact, a bigger cam with a 3.36 or 3.54 diff wouldn't be much fun at low revs since there's less torque than stock. The idea is to get up into the power band as soon as possible and then stay there when you shift to the next gear.

As suggested above, the Transmission Calculator site http://www.geocities.com/z_design_studio/transmission.html let's you simulate any combination of transmission, diff, and tire size and see both what the max speed is in each gear, and also what your cruising rpm would be at any speed in any gear. I found it very helpful when planning my swap to pick a few typical speeds that I drive a lot (70 on the freeway, 35 and 45 on secondary roads) and compare what the revs would be with what I already had. I really like the combination of late 5 speed, 4.11 and larger cam but it wouldn't be for everyone, especially for those who like to keep the revs low and not shift a lot.

m4xwellmurd3: this should help. if it doesn't come through as a link, just type it into your browser...

http://datsunzgarage.com/trans/

Actually that chart is incorrect. The 4spd. in the 70/71 Model Year - type A was not the same, nor did it have the same gearing as the 4spd. used 72-74 Model Year type B.

Secondly the 5spd. in the 1980 280ZX is different in its overdrive 5th.. 0.773 for 1980 model year and 0.745 for the 81-83 model year.

FWIW,

Carl B.

I'll go with Brian Little on one thing, the 5 speed that you have is probably the one for you. Neal G might be in a different boat though, because he has his choice. I'd return the early 5 speed and try to locate a later one because that was what he wanted in the first place.

I'll admit that I have an early 5 speed and 3.9:1 R200 and enjoy the combination because I don't happen to have an alternative. If I could I'd go with the later 5 speed if only for the better overdrive ratio to not turn 3,500 RPM at 75mph. Then again, what would I do with a used '78 5 speed in southern Utah? They just crush the cars here because no one is looking for parts for them.