Transmission identification

[Dewme5]

Anyone have a link for a good trans identification site?

I was told the previous owner swapped in a different trans. It should be a 5mt fs5w71c. Problem is I only have four forward gears.

I'll get a few pics, in case someone here knows.

[Dewme5]

Looking forward at the bellhousing bolt pattern
https://lh3.googleusercontent.com/-tucgDGUtxFs/T4A-Wiww2SI/AAAAAAAAAXI/U6kY2hgo6K4/s640/2012-04-07_08-12-20_871.jpg

Driver side, rear end of trans, I assume the speed sensor. Speedo checks out pretty close.
https://lh4.googleusercontent.com/-HW3QfglfLvY/T4A-cwf0g_I/AAAAAAAAAXQ/dajelNk-2YQ/s640/2012-04-07_08-11-42_870.jpg

Passenger side, ZL71B #2 NMCA written on it. Also, there is a second sensor here, located where the gray connector is, in the middle of the pic. I assume this is the reverse light switch.
https://lh6.googleusercontent.com/-QelKtt1UAS8/T4A-i0makdI/AAAAAAAAAXY/suFWH6Ff6k8/s640/2012-04-07_08-08-00_406.jpg

Passenger side, immediately in front of shifter. Not sure what sensor this is.
https://lh6.googleusercontent.com/-5uO6WJyYZgg/T4A-tL7F_RI/AAAAAAAAAXg/8zYhUZ4QlFs/s640/2012-04-07_08-07-35_624.jpg

Top loader, with 4W71C written on it.
https://lh3.googleusercontent.com/-RVaMBZN-k2I/T4A-1n3YSGI/AAAAAAAAAXo/oEwn7FXYk8w/s640/2012-04-07_08-07-18_893.jpg

I just replaced the starter two days ago, and the correct starter for my truck fits this transmission.
95 pickup, 2.4 KA24E, should be 5speed, Manual, 2wd.

I need to replace the trans output shaft seal to stop fluid from leaking, but it seems that the seal does not actually touch the yoke. Yoke measures 1.38" which is correct for the original trans. If my assumptions are correct, this is a RN4F31A trans, which has a 1.575" ID rear seal. If I can get the transmission identified, I can start fixing my problems.

I would ask the original owner, but he's locked away.

[Dewme5]

I'm sort of confused now. I cross referenced measured sizes, and came up with the correct seal for the original transmission. I bought a National seal, PN 710324, which checks out to be the right part number for the transmission that should be in the truck. The seal I pulled out however, had a 1.575" ID, which did not even touch the yoke which is 1.738"

Is it possible this transmission is the correct 5 speed, but 5th gear is locked out somehow? There is no attempt to go in, no bump or notch that I feel.

I'm new to Nissan, but I was told it was a 4 speed, and it sure feels like one. However on the Borg-Warner T56, there is a factory 1 -> 4 skip shift below a certain rpm range. a solenoid prevents second and third. Does Nissan have something that locks out overdrive. I've read of such a thing on the automatic transmissions.