Guys im trying to source a "260z close ratio" 5 speed for fittment to L20b.

Now whilst searching I have come across some information that leads me to believe all the 2xx series were close ratio?

see here: http://members.optushome.com.au/amaxeng ... earbox.htm

Or is there a particlular 260Z box that is "closer" than the others?

If so, how can I identify this close ratio gem.

Confused,

Mal

hmm ok but I dont know how accurate turning the shaft will be to determine ratio , if there is no other way to identify these boxes.

Your saying 2.9 for first the link I gave and other info I have googled say 3.321.

Does anyone know if there is external markings and or codes to identify the 260z close ratio?

is it a different box from standard or all 260z the same? 240z also?

Cheers,
Mal

sean thanks for your help.

How would counting input shaft vs output shaft revolutions on a small diameter shaft on a dirty old gearbox with an eye level on where a fixed point is screams out innacuarcy to me.

sure we can decide betwen roughly 3 or roughly 3.5 but I would have thought decerning between 2.9 and 3.3 would be impossible for all but the most skilled of bush mechanics.



Thanks for the help.

The info referred to is stuff I put on the OZDAT list 3-4 years ago. I see it has been messed around with a bit. The main changes need are in the table section.

There are two variations in the 2.9 first gear boxes. First variation is the 71A box with detachable bell housing, (same as the early 2000 sports box). The 71A box was upgraded in the 240Z in December 1971 with a 71Bbox. The 71B had bigger bearings and the bell housing was made integral with the housing back to the sandwich plate. There were also also other improvements in the 71B box. The 71B continued through the 240Z and all 260Z's. The 280Z went back to a 3.3 first (for the heavier vehicle).

The main problem with 71B boxes is they are old and get cracked teeth and tooth root failures. They also get broken dog teeth on selector rings (hard to get) and worn servo springs in the syncro's that helps cause the dog teeth problems.

As Sean said, it is easy to tell the first gear ratio by turning the input shaft and counting a full turn on the output shaft. Fit an old clutch plate with an index mark on the input and you can easily tell if it is 2.9 turns or 3.3 turns from your index point. Filler is on the right side of the box as stated. This is the easist way to tell the boxes apart.
Hope this helps.

_________________
Cheers
Feral Errol

Thanks Errol.

So basically the 240z after Dec71 through to the end of 260z are all the "close ratio" box people speak off.

The clucth plate is a good idea, my inexperience is what made me doubt the accuracy of Seans method, thanks for clearing that up.

Im off to find me one

Cheers,
Mal

Basically that is correct.
Other differences between the OEM 71A & 71B boxes is that the A has a flange output & the B has a slip-yoke.
The A also has the monkey-motion shift mechanism (same as 510/610 4-speeds)

These boxes are considered 'close' by designation (FS5C71A/B), but are not the same as the Option boxes with close ratio sets (1:1 5th).

_________________
Ben
Adelaide,
South Australia
L28ET 240Z
RB25DET WGNC34 Stagea RS-FourV

YEP,
Good point about the flange shaft Ben. They still used the flanged shaft in the 71B boxes up to jun 1972 when they went to the slip joint shaft.
The size of the selector forks changed on the 71B as well and became a little more robust. Lots of snmall things to increase reliability basically.

_________________
Cheers
Feral Errol