L28 into a 71 240 trans question

[Advocator]

After years of letting it sit I've purchased an L28 for my dads originally owned 1971 240z but in his stubborn ways he refuses to change it to a 5speed and loves his automatic trans.  I've agreed to go along with his idea but I'm trying to find out what are my options of putting an automatic trans that will bolt right up to the L28.  I've looked around the forums and done some other research but was unable to find an answer so here I am looking for help.  If some cutting or extra work needs to be done I've got a friend helping us with much more experience than myself but I need to know what will and won't work.  

[NewZed]

Pretty sure that the L28 will swap right over on to the current L24 auto trans.  Why would you think any differently?  They're the same block.  Make sure you swap the spacer over also from the L24's crankshaft.

[Advocator]

the current L24 trans would bolt right up I do realize this.  But I'm looking for a 5speed auto trans not a 3

[NewZed]

You didn't really specify.  Never heard of 5 speed Datsun automatics but it looks like other countries might have had them.  Good luck.

 

http://en.wikipedia.org/wiki/List_of_Jatco_transmissions

[Six_Shooter]

You didn't really specify.  Never heard of 5 speed Datsun automatics but it looks like other countries might have had them.  Good luck.

 

http://en.wikipedia.org/wiki/List_of_Jatco_transmissions

 

I read it the same as you, wanting to bolt the original 3 speed Datsun trans to the L28.

 

5 speed automatics are not very common and I only recall them being available in the last few years, from a few domestic manufacturers, though admittedly I don't like automatics, so I don't keep up on all automatic trans offerings. If you do find something in the 5 speed variety, you will need to make an adapter plate and flexplate spacer, which may or may not be too difficult. I'm in the process of making an adapter plate to retain my 5 speed manual Nissan trans and mate it to a GM engine I am swapping in. One portion of the adapter plate is proving to be difficult to finalize how I will attach everything and retain dowel pins.

 

Any reason you want to swap out the 3 speed?

[Advocator]

tell me if I'm wrong but with the current L24 trans and and original L24 motor it seems to top out around 115-120 but driving it down the highway at 75mph's it was running at about 3200-3800 rpm's and doesn't feel healthy.  With a bigger motor and same trans I'm afraid of a complication with reliability 

[Sideways]

 at 75mph's it was running at about 3200-3800 rpm's and doesn't feel healthy.  With a bigger motor and same trans I'm afraid of a complication with reliability 

600 rpms in top gear should make a pretty substantial difference in speed.  Either way- Why are you worried about reliability in this scenario?

[Six_Shooter]

Regardless of engine size, it takes the same amount of power to maintain the same vehicle (weight unchanged) at the same speed, so the drivetrain will not experience anymore strain after the L28 goes in than before. What I'm saying is the reliability will be the same.

[NewZed]

driving it down the highway at 75mph's it was running at about 3200-3800 rpm's and doesn't feel healthy.  With a bigger motor and same trans I'm afraid of a complication with reliability 

With a bigger, torquier motor, you could just change the rear diff ratio to get the highway RPM down.  What ratio does the car have now?  The 73 automatics came with 3.54, you could go to 3.36.

 

Seems like you might just be assuming about things you need, and things that are possible.  You don't want a 5 speed auto, you want an auto with overdrive.  Which doesn't appear to be available for the L engine.  Who knows though, maybe you can swap the bellhousing with a more modern transmission.

[m1ghtymaxXx]

Just food for thought, 240SX manual transmissions accept an L series bell housing, what about looking at 240SX automatic? No clue if it works, but perhaps worth looking into.