Trans #s on bellhousing

[Brian Netols]

I have been trying to identify the 5spd transmission in my 73 240Z (originally a 4 spd). It was installed 16years ago and I cannot remember what car it came from. I have read about the trans types, all of which have codes beginning with F. I have also read many threads, including one which said that there are no stampings which mean anything. However, my 5spd has this number stamped on the top of the bellhousing -T7Y09774. What, if anything does it mean? In tryng to ID the tranny, this may help. Since I never changed the speedo gear, every since the swap, my speedo reads more than 10mph off, too low, in top, now 5th, gear. Thanks.

[Bruskiz]

The speedo gear needs to match to your diff ratio. If you still have the original rear diff, then its 3.36 ratio.

Mike

[Brian Netols]

Posting from work today, sorry for the new post.

I am sure that I still have the original rear end - 3.36, because the car was bone stock when I bought it in 1981. I am trying to figure out what trans I have. I think that it might be out of a Turbo ZX because the wheels I have are the 15" Turbo ZX wheels (look kinda like a swastika) and I beleive that the wheels came off of the same car that donated the trans, and maybe the block, though the heads are definitely N42.

[Bruskiz]

Pics of 5 Speed Trans This should help. And you probably don't have a turbo 5 spd (BW T5). There not a direct swap.

Mike

[Brian Netols]

Thanks for the link, it should help. I agree that it is unlikely that it is a T5. But the mechanic (since retired) who did the swap, was very knowledgable about Z's and had a complete machine shop in his garage. The swap was not a simple pull and replace. I saw the entire engine and trans completely apart and being blueprinted and balanced. I know that he overbored, honed and decked the block in his shop. So a more complex swap was within his ability. (he did a complete resoration of a MG Midget for my father which started with the car in bags and ended with it looking like it just came off of the assembly line - except that it was dead bang reliable).

From looking at the link with the corresponding rear end and 5th gear ratios, my guess is that I have a 5 speed out of an 81-83 non-turbo. The car takes a while to get there, but has serious top speed with the 3.36.

I am learning more about how much I forgot about my car every day. Also I take it that the serial number on the belhousing means nothing?

[Victor Laury]

Sounds like your settled that you have a FS5C71B from a "pre T-5" turbo ZX.

If you'd like to be sure of which gear set you have, I have a test for you to perform.

If your tranny is out of the car, you can determine the overdrive ratio and ID the gear set with that ratio.

1st you need a guide

Marc Sayer's tech tip on trannies

is the first one I found today, there is others online as well.

Now remmeber overdrive means the output shaft moves a greater distance than the input shaft. When I did this test, I marked both input and output shafts straight up. I turned my output shaft one complete rotation. My input shaft rotated .773 of one rotatation (as a clock, the big hand a touch after 9 o'clock).

As you can see on Marc's chart, this indicates I bought a 1980 ZX transmission, and now I know all my ratios.

1977~79Z&XZ = .864 = almost 11:00 oclock

1980XZ = .773 = a little after 9:00 oclock

81~83ZX = .745 = a little after 8:00 oclock

[Brian Netols]

I am not settled yet. But there is a more noticeable "gap" between 1st and 2nd than between 2nd and 3rd. I learned never to short shift first. Also, the increase and decrease in revs at a given speed when shifting from 4th to 5th and back is about 25%. Both of these factors are consistent with a 2-3 close ratio 5 speed with a .750 overdrive. I am going to go check the code on the block to see if it is consistent with an 81-83 trans. Can I see if the trans has one ear or two without putting the car one lift?