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Which 240sx tranny fit in a 240z


rick240zed

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  • 3 months later...

Hey guys, just had a simple question for those who have swapped their 4 speed to the 5 speed 240sx transmission. Did you guys have to move the reverse switch forwad or were you guys able to keep it in the same location? I currently have everything hooked up, but my reverse light stays on. Out of all the documented swap only a couple of guys mentioned in their post they had to move it forward on their 4 speed, but i'm not exactly sure why or if it was necessary.

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The switch is located over the reverse gear mechanism of the transmission, probably the shift fork.  It can't be moved anywhere.  You may have plugged in to the wrong switch, like a neutral indicator switch.  Use an ohmmeter or test light and find the switch that closes when the shifter is in reverse location.  Or just try them all until one works right.

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Seems like a lot of work for pretty certain.  Have you logic'ed things out?  You said the reverse lights are always on.  Meaning the switch contacts are always closed.  You might be able to back the switch out a few threads to get the contacts to open.  Or you might just have a stuck switch,  You can probably swap it with one of the extra ones, from under the car.  Even if you took the transmission out and removed the front case, that's probably what you'd end up doing anyway.

 

I have a 1985 71C transmission with a ZX bell/front case on it.  It's sitting in the garage so I checked the switches.  The reverse switch is the one directly in front of the fill plug on the right side.  It works fine, reverse = beep, anything else = silence.  There's also a neutral switch on the back half, right side.  Good luck, don't get carried away.

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I tried all the suggestion, the switch and wiring tested out good. I even had someone watch for the reverse lights to kick on while I was threading in the switch hoping that would do the trick, but it stayed on out of gear. At this point I'm thinking of just leaving it and maybe fix it the next time I have to get in there or make a switch, but thanks for all the help NewZed greatly appreciated.

Edited by voong413
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I even had someone watch for the reverse lights to kick on while I was threading in the switch hoping that would do the trick, but it stayed on out of gear. 

Not really understanding what's going on.  You say waiting for them to kick on, implying that they were off, but then say that they stayed on, implying that they were already on.  And the switch and wiring test out good.  ??  Anyway, your car, your problems,  Something to work on.

 

You could always just wire in a console switch in the meantime, until you figure it out.

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Well I first tested the wiring by touching them together to trigger the light, which confirmed the wirings were good. The reverse switch is spring loaded at the tip, so with it out I bench tested it by depressing it to trigger the light and I also ohm it. My testing lead me to believe that I might of over tightened the sensor causing it to always stay in contact. I checked my theory by threading in the mechanical sensor just far in enough to trigger the light with the car in reverse. If everything functioned like it should, the reverse light would go out when I shift the car into neutral, but the light stayed on which made me believe people moved the sensor forward because the bell housing didn't match up with the new transmission gears and shaft to trigger the light properly

Edited by voong413
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I can't imagine someone drilling a new hole.  Where would they put it?  I think it sits in the notch in the shifting rod, and is actuated by the edge of the notch.   You can see it in the sixth and seventh pictures of Post #10 in this link - http://www.classiczcars.com/forums/engine-drivetrain-s30/49070-transmission-id-quiz.html

 

Lots of swaps done and no reports of reverse switch weirdness.  Maybe get a mirror up in the hole and see if something's bent inside and can be nudged aside.  Maybe your shift rod is 180 off, did you repair any shift fork damage?  You should be able to see that notch.

 

You might be right, there could be something wrong inside the transmission.

 

 

Edit - Found that reference you talked about.  Apparently the four speed front cases had the switch in a different spot.  Meaning they must have used a different style shift rod.  I used a ZX 5 speed housing so no problems for me.  You could probably fix it just by swapping shift rods, I would guess, or machining a new notch in the rod.  Might be easier than machining a new hole in the case.  Still, a look through the hole will probably tell the story.  Sorry to monopolize your thread, good luck.

 

http://home.comcast.net/~zheimsothtn/Transmission2.htm

 

"

  • Here's one I haven't seen mentioned before; the reverse gear switch is located about 22mm further back on my F4W71B than on the FS5W71B or C. Since I didn't realize this until after I chose the 4 speed bell housing to modify (it was already out of the car), I had to drill and tap a new hole in the side of the case to make my reverse switch work. If you're using a 5 speed 71B bell housing, this is not a concern."
Edited by NewZed
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The new hole is shown in the link I edited in above.  Since it's on the rod, it's just 22 mm forward.  Who knows, there's not much to it, you could probably get it right with a hand drill and a tap.  If it was me and I had everything all put together and working, I might even drill and tap without taking it apart, but with the transmission out, on its side and working from underneath so the chips fall down and out.  But I'm lazy and like an odd challenge.

 

You can also see the notch on the 71C shift rod in his pictures.  

 

Looks like that would be your problem source sine you started with a 4 speed housing.  A measurement of hole location comparing the two housings would also tell.  There should be a 22 mm difference.

 

http://home.comcast.net/~zheimsothtn/Transmission2.htm

Edited by NewZed
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Thanks for all the information guys, the different bellhousing was actually the reason why I started questioning if I had to move the location of the reverse switch. Tamo3, it was actually that post that had me question if my bell housing would work. I used the  4speed L2 bellhousing for my swap, and according to the post it looked identical to the 5speed L2 housing. Granted it was never actually stated, I made the assumption the 2 bellhousings were identical. Can you confirm if the 2 housing were the same and if any modifications were done to get the reverse switch to work?

Edited by voong413
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  • 2 weeks later...

If you use a 4-speed bellhousing, you need to move the reverse switch forward.

 

Some 5-speed bells have the switch moved up already, some do not. All 5 speed bells that I have seen have the boss for the forward-mounted switch, even if the switch is mounted in the rearmost boss.

After 75 or 76, I don't thnk you need to do that. The 79 four speed has the reverse switch in the same spot as the five speed of the same year. I think pre 280Z (240/260) had the early switch position.

 

It MAY have changed in the half year 260Z... I have my original early Skinny Bumper 260 Bellhousing prepped for this swap along with several other later five speeds from failures set up as selling spares and IRC the switch hole being positioned identically.

 

I would make book on an across the board change in transmission casings around 12/73 or 6/74 for the S30 transmissions...

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