73 240z 3 speed auto swap to maxima 4 speed

[ez 73]

I am thinking about swapping my 3 speed auto to a maxima 4 speed w/overdrive My tranny is a 3n71b. the 82-84 maxima/84-89 z31 tranny is an 4n71b Do new transmission mounts have to be fabricated? can I use the drive shaft from a z31,instead of shortening mine,can I use my existing flex plate? I understand this was covered in 2006 by " hisandherz " I couldn't find the thread. I also heard that they were talking about a 76 280z or zx I don't know if that makes any difference. Any info you could give me on this swap would be appreciated

[HowlerMonkey]

The maxima 4n71b is a short tailshaft trans. and should be the exact same length as the 3n71b long shaft transmissions.

 

The one I had (1984) had a 38mm outer diameter on the driveshaft yoke and simply putting the calipers on splined output shaft of the tranny was 27mm.

 

Another maxima 4n71b had a 35mm outer diameter of the driveshaft yoke and the calipers showed that the splined output shaft was the same thickness as the 3n71b trans. for a non-turbo 280zx from 1982 (less than my caveman measurement of 27mm from above).

 

A 3n71b from a 280zx turbo has the thicker output shaft (27mm)as referenceed above but with the 35mm outer diameter of the yoke.

 

The maxima 4n71b from 1984 uses a very strange way for the transmission mount in that it is a bit of a cradle with two mounts on either side which mount to the tailshaft housing bolts.

 

One other thing to consider is that some with the first generation maximas trying to go from a 3n71b to the 4n71b had transmission tunnel clearance issues around where the tailshaft housing mounts to the transmission case because it's a bit larger than the thin and long tailshaft from some 3n71b.

 

The floor pan is different between the manual/3n71b maximas and the 4n71b maximas because of this.

Edited August 13, 2012 by HowlerMonkey