interesting discovery...
 

well, I blew my transmission the other day, and was forced to either a.spend 500 dollars to get it fixed, or b. buy a used 240Z transmission. I went with option a., and I bought the transmission from John down on Camp Pendelton. When I went to pick the tranny up, I noticed that it looked slightly different from the one that I had previously in the car, such as the shifter looked different. I was installing the new tranny today, and was also looking through my haynes manual, and noticed that the transmission that I used to have in the Z was a 260 tranny, and the one that I had just bought was the stock 240 tranny. The question I have is this: why would a person want to install a 260 transmission into a 240? Is there any kind of performance gain? All comments appreciated.

I just looked through my haynes manual, and I noticed that if you were to compare the gear ratio of the 240 tranny to the 260, the 240 is geared lower, with a 3.549:1, as opposed to 3.592:1. What exactly does that do?

The ratio you are looking at right there I'm pretty sure is the rear diff. gear not 1 of the tranny gears. But to answer your ? anyways the lower the gear ratio number is the more top end speed you have in that gear and the slower the acceleration your car has and the higher the gear ratio the lower top end speed is in that gear and the faster the acceleration is.

I don't know if I know how to answer your ? though because what do you mean by better performance. Top end speed or acceleration?

basically, I just want to know why someone would want to put a 260 transmission into a 240.

they probably had the tranny on b/c it was just what was available to them. Maybe the other tranny went bad and they were forced to put the 260z tranny in as a quick fix thats most likely what happened

actually, he's looking at the 1st gear of the transmission:


240Z
3.549
2.197
1.42
1.00
n/a
'70-'73

260Z
3.592
2.246
1.415
1.00
n/a
'74-'78

280Z
3.321
2.077
1.308
1.00
0.864
'75-'79

280ZXa
3.062
1.858
1.308
1.00
0.777
'8/79-'80

280ZXb
3.062
1.858
1.308
1.00
0.745
'81-'83

280ZXT*
3.500
2.144
1.375
1.000
0.780
'81-'83

there's all Z transmission gearing that you have.

Sorry my bad

EZ math
 

Here's a good way to compare gear ratios. If you divide the smaller number by the larger number you will get the percentage of change. Example: 3.549 divided by 3.592 =.988. So if you go 35 mph in first gear, you will be going 34.5 mph with the 260 trans at the same rpm. If you compare the other gears you will also see very little difference. The later 280 transmissions used a different ratio rear end, making top speed less in 4th gear, but getting it back in 5th. You can use this formula for comparing rear end gears too. Bottom line, you will not be able to tell the difference between the 240 and the 260 trans. One more thing, the shifters are the same for 70-71, a straight stick that has a nut holding it in the shifter mechanisim. The 72-79 has a curved stick that goes in a socket in the shift mechanism and is held in with a cross pin and clip. The distance from the front of the trans to the stick is about an inch or so longer in the 70-71. The shifters in the picture is for the later trans.