T5 vs 4-speed

[Apollyon12]

I have two 71's, one has a working '72 4-speed (needs speedo fixed though) and the other has a supposedly good T5 with centerforce clutch. The car with the T5 is my parts car, and supposedly hasn't been driven since '89 but is supposed to still be in good shape. I am building a Prepared Autocross car, sticking with an n/a datsun motor and am not planning on going too crazy with the power.

 

Does anyone have any experience running both transmissions? From what I am told the 4-speed will be ok, less shifting while running high RPM's. The T5 is supposed to have small 1st and 2nd gears which would mean a good deal mor shifting, but better RPM's and fuel consumption on the highway. I have heard of doing an electric overdrive mated to a 4-speed in Triumphs and had though of looking into that too. Right now I am debating whether or not to sell the T5 or keep it on the shelf to try it out in the future.

[JMortensen]

I hate the wide gears on the T5 and the Nissan 4 speeds, and went with a 280ZX box from 1980 which has a slightly closer 5th than the later 81-83, and has tighter 1-4 ratios than the 76 or 77 up to 79 (yes, 1st year of ZX too) transmissions. Don't change the trans and forget about the diff though. The close ratio transmission really requires that you have a fairly low rear end ratio. 3.9 or lower preferably. The really serious guys like the comp boxes.

 

The less shifting you have to do the better. If you can shift it into second and hit the top speed you expect (say 70 mph) that is probably the best you can do. Basically get off the line, shift to 2nd, and forget about shifting. Left foot stays on the brake, right on the gas, and you 're good to go until the end of the run.

 

You can use a calculator like the one below to figure it all out:

http://webspace.webring.com/people/cz/z_design_studio/

[Apollyon12]

Wasn't the R200 the limited slip rear end?

[JMortensen]

Not all of them. In fact very few of them are LSD. Do a search, read my sticky in this forum you'll find what you need.

[Apollyon12]

Ya, i thought of that right after I hit post.

 

Anyway, that calculator didn't work for me, but I see that the gear ratios for the T5 and the early 4-speed seem really close to me.

 

T5 with ratios of 3.5,2.144,1.375,1,.78

4-speed with ratios of 3.549, 2.197,1.42,1

 

With the same rear end ratio (and therefor not part of the calculation), the difference between the two first gears is only 1.4% and between the two second gears is only 2.4%. To reach the same rpm after the transmission (rpm that is going to the rear end), you have a difference of 112 and 192 at 8000 engine rpm. That doesn't seem like enough to really be able to feel any difference.

 

Am I missing something?

 

Of course if you where using a different rear end with each tranny, there definitly would be a difference.

[Apollyon12]

Wait, I think I was compairing the wrong ones.

 

What you where saying is that the T5 and the 4-speed ARE very close to each other, but that the '80 5-speed was significantly different.

 

4-speed

1) 3.549

2) 2.197

3) 1.420

4) 1.000

 

'80 5-speed

1) 3.062 (15.9% lower - 1272rpm difference)

2) 1.858 (18.2% lower - 1456rpm difference)

3) 1.308 (8.5% lower - 680rpm difference)

4) 1.000

5) 0.773

 

That would be a signifigant difference.

Edited October 30, 2010 by Apollyon12

[JMortensen]

There you go. And the 4 speeds came with 3.36 or 3.54 gearing, the T5 came with 3.54, and the 280ZX came with 3.90. If you have to shift to 3rd in the 4 speed, the T5, or the early 5 speed, you're going to lose time not only because of the shift but also because the 2nd to 3rd gap is so big relative to the close ratio transmissions. If I were choosing between the 4 speed and the T5 I'd go with the 4 speed. I believe it is lighter and the shifter is better. Might be that you can get a better shifter for the T5, dunno about that.

[Apollyon12]

I think I made a mistake. When I looked at the transmission in my parts car orginally, someone had told me that if it has a removeable bellhousing it's a T5. I took their word for it and didn't research it any more. When I looked at the tranny, I could see the bolts inside the bellhousing holding it to the rest of the tranny. It's kinda hard to see in the pic, but they are there.

 

 

But this is DEFINITLY not a T5. The shifter is wrong, it's the same design as the one in my 4-speed. It does have two ears down by the shifter, but doesn't look like all the other pics of 5-speeds I have seen.

 

I am going to see if I can find some markings or numbers tomorrow when it isn't raining, but I can't see any when I look down from the engine bay.

[NewZed]

Here's a link with some good pictures of the later 5 speeds, including the Borg Warner. If the shifter hangs off the back on a cylindrical mount and it's a 5 speed, it's one of the FS5W71Bs.

 

http://www.az-zbum.com/information.transmission.shtml

[Nigel]

There was a very early ('69-'71) Nissan 4 speed transmission that had a bolt on bellhousing. The model number is F4W71A. That may be what you have. There was also a 5 speed version, but it was not sold in North America.

 

Here's a link to a picture of the 4 speed, but you need to log into classiczcars.com to see it:

http://www.classiczc...35&d=1236126937

 

Nigel

'73 240ZT

[Apollyon12]

That pic on ClassicZCars looks exactly like mine. Unfortunately, I just took the time to pull it out of the car. Apparently, whenever I checked for a 5th gear, I was sliding back into fourth because the tranny was rocking around due to the lack of motor. So I have an early 4 speed out of the early '71 and a late 4 speed in my late '71.