What is the conversion for, and extra gear (overdrive) or for serious track (drag) work??

I'm using an L4n71B behind my L28 with great success. On the highway, it substancially drops the revs down with an 0.686:1 O/D ratio.
Compared to the L3n71B, 1st and 2nd gears are a little lower for more torque. For me in my heavy street car, this is a bonus.

In Australia, VL Commodore Turbos (a GM/H car) used the RB30ET Nissan engine. The L4n71B boxes in those could handle extreme power ups with suitable modifications. I consider these Jatco's to be pretty tough. Something to consider perhaps.

Cheers.

Quote:
What was required to run the L4n71B box behind the L series? direct bolt up, adapter plate needed, etc
The L4n71B ia s hydraulically operated trans. The E4n71B is a later version that is controlled by a dedicated ECU.

I personally like the idea of running a purely hydraulic trans because of its simplicity. For the street, I run an adjustable vacuum modulator valve that lets me determine the shift points somewhat in relation to engine vacuum.

You might be able to source a US Nissan/Datsun L series that came with a 4 speed trans. In Oz, the R30 Skyline had the L24E engine and the last run of those in 1984-5 had the L4n71B. From then, when the R31 came to Oz, they had changed over to the RB series so the belhousing was changed and the trans was upgraded(?) to electronic control. Also, as mentioned, these transmissions came in GM VL Commodores.
If you can find one for the L series, get the flexplate as it is different to the one for the 3n71b. The other changes include building a new crossmember to suit the different style of mounting. Not really hard to adapt if you can weld, so grab the crossmember if you can. The output shaft is larger so you'll need the first part of the tailshaft (prop shaft) to have it adapted to yours. (I had to do all of this to make it fit into my machine!! Not particularly cheap, but I'm very happy with my conversion.)