Which transmission is this?

[duballstar37]

Originally Posted by Kingtal0n

you can get two different 5-speeds in the same year

some have reverse synchros, some not,
some have different 5th gear ratios
some have updated shift fork hardware
silvia trans is similar to but many differences from KA trans including synchro rings

The only really important thing that makes any difference is the gear ratio of 5th, and the fork if you can get the good ones, or install a good 5th fork (they break and lead to infamous 5th grind)
The s13 trans have shorter ratios, the S14 trans has a better cruise ratio, so we always want the identify and use the better overdrive for economy

spin output shaft vs input shaft and try to identify the ratio of 5th

Can you please elaborate on the difference in gear ratios between S13 and S14 transmissions? I swapped a S14 KA trans onto my S13 SR (swapped the bellhousing) and the gearing felt identical.

[jr_ss]

Originally Posted by duballstar37

Can you please elaborate on the difference in gear ratios between S13 and S14 transmissions? I swapped a S14 KA trans onto my S13 SR (swapped the bellhousing) and the gearing felt identical.

All USDM transmissions have the .759 ratio for 5th or overdrive. The transmissions that back the Sr20de and DET come with varying 5th gears. Depending on what motor you have, some are .759(S13) and some are .838(S14/15).

[Tieny]

Originally Posted by duballstar37

Can you please elaborate on the difference in gear ratios between S13 and S14 transmissions? I swapped a S14 KA trans onto my S13 SR (swapped the bellhousing) and the gearing felt identical.

Gears 1-4 are identical between the KA and SR trans. The SR trans will have a slight higher gear ratio (0.838) than the KA trans (0.759) with a few exceptions in some Silvia models that also have an SR at 0.759. At highway cruising speed with the SR (0.838) you'll probably sit at a higher rpm compared with a KA (I wanna say probably about 300-500 rpms higher?)

If transmission is benched, one way to check is by marking a tooth on the output shaft. Put it in 5th gear and spin the input shaft one revolution. If the mark is now 7-8 teeth away from the original position it has a 5th gear ratio 0.759. If 4-5 teeth away, 0.838.

Originally Posted by Kingtal0n

you can get two different 5-speeds in the same year

some have reverse synchros, some not,
some have different 5th gear ratios
some have updated shift fork hardware
silvia trans is similar to but many differences from KA trans including synchro rings

The only really important thing that makes any difference is the gear ratio of 5th, and the fork if you can get the good ones, or install a good 5th fork (they break and lead to infamous 5th grind)
The s13 trans have shorter ratios, the S14 trans has a better cruise ratio, so we always want the identify and use the better overdrive for economy

spin output shaft vs input shaft and try to identify the ratio of 5th

While rebuilding my trans I found (at least on my model trans) that the only thing that actually engages 5th gear is a small retaining clip on the 5th fork rod. This clip is forced against the fork which engages the hub. It was somewhat warped, loose, and was free to spin. Once this clip breaks off it ends up getting incomplete 5th gear engagements.

My trans has a 0.759 gear and does not have a reverse synchro. After searching for a long while I haven't found any full rebuild tutorials anywhere on the net for a 240 transmission. I'm thinking of possibly making a video of a full teardown disassembly and rebuild.