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.

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

Mike

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.

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

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?

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

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?