I’ve recemtly acquired a close-ratio 5-speed that, I assume, is a FS5W71B. While checking over and cleaning it I see there is a marking that says “#2” (see left side of photo). The # is part of the casting but the 2 has been manually stamped into the aluminum. Being curious, I did some googling and didn’t find anything other than some information on “competition” transmissions that could be had with three different gear set options, described as “1”, “2”, and “3”. Anyone know if this stamping of a 2 denotes the transmission as being a competition variety? Or is it just a common stamping that references something else? I haven’t yet turned the input shaft to count the rotation of each gear.

5 hours ago, 268Z said:

Anyone know if this stamping of a 2 denotes the transmission as being a competition variety?

It's a casting foundry mark to identify tooling used when the case was made. Nothing to do with what's inside.

The competition-oriented versions of the B-'boxes (your 'Option 1, 2 & 3') were Servo (steel) synchro 'boxes with Direct Drive (1:1) fifth gears and 'Dogleg' shift patterns (1st gear left and back, opposite Reverse and 2nd thru 5th in conventional H pattern). Correct name for one of these Direct Drive 'boxes is 'F5C71-B' (note no 'S').

Yours is likely just a normal FS5W71-B.

There were two variations of the ZX 5 speeds, according to the FMS's. Only the 5th/overdrive ratio changed.

I don't know of any way to tell the difference externally in the two ZX close ratio boxes other than opening it up and counting gear teeth.

You can count revolutions in 5th gear. .745 is less than 3/4, .773 is more. 3/4 is fairly easy to lock in on. I had a .773 and that worked for me. Also had a .745.

OK.Ya that answers my curiosity. Figured it wasn’t a super rare transmission but thought I’d ask.

I’ll check 5th gear when I get home to see what rario it is.

9 hours ago, HS30-H said:

It's a casting foundry mark to identify tooling used when the case was made. Nothing to do with what's inside.

The competition-oriented versions of the B-'boxes (your 'Option 1, 2 & 3') were Servo (steel) synchro 'boxes with Direct Drive (1:1) fifth gears and 'Dogleg' shift patterns (1st gear left and back, opposite Reverse and 2nd thru 5th in conventional H pattern). Correct name for one of these Direct Drive 'boxes is 'F5C71-B' (note no 'S').

Yours is likely just a normal FS5W71-B.

Unsure if the is accurate info, but I think I recall seeing that the transmissions with two ears at the back were the 79-80 boxes and the 81-83 only had one:
https://www.classiczcars.com/forums/topic/64504-fs5w71b-transmission-identification-close-ratio-vs-wide-ratio-with-pictures/?_rid=2858

Ratios I put into a spreadsheet a long time ago:

Edited January 30Jan 30 by inline6

Thanks, inline6. The transmission I’m working on has the single ear. I believe the1980 FS5W71B was the same as the ‘81-83 5-speeds, with the only difference being a different over-drive ratio. I’ve confirmed, via turning the input shaft and comparing the rotations in 5th gear of the output shaft, that mine is the ‘81-83 variety.