Conversion question

Post by **240TKE128** » Mon Dec 25, 2017 8:43 pm

K so let me start off with 2 things.

1. I know this is crazy and not normal no hating I have medical reasons with family for the question.

2. I've been searching for days and everything I've found says it's not possible due to computers.

So I am wanting to convert my 240sx from manual to automatic, I won't be keeping same engine or anything, so my question is this if I'm already swapping out engine transmission and computer, is there any real issues to doing the conversion or something I am missing.

Post by **MikeRL411** » Mon Dec 25, 2017 11:27 pm

It's probably cheaper to buy an existing 1990 240SX with factory Automatic transmission !

Post by **240TKE128** » Tue Dec 26, 2017 9:52 am

So the price isnt the issue on this, its more of the feasibility, my understanding is its only the computer that typically is a factor, is there something else that affects it that makes it harder?

Post by **centralcoaster33** » Tue Dec 26, 2017 11:21 am

It's a bit of work, but a manual to automatic transmission swap can be done for sure. There is no real issue I can think of except for you saying you're not keeping the same engine. What do you mean by that? Here's a link to a very good automatic to manual swap article. You'll be doing the thing in reverse of course. Your engine and your automatic transmission will need computers to control them. Your mention of an engine swap makes all of that pretty unclear. Your transmission needs to be paired with your engine and the computer.

auto-to-manual-writeup-5-speed-conversion-t181139.html

Post by **240TKE128** » Tue Dec 26, 2017 12:25 pm

centralcoaster33 wrote: ↑
Tue Dec 26, 2017 11:21 am
It's a bit of work, but a manual to automatic transmission swap can be done for sure. There is no real issue I can think of except for you saying you're not keeping the same engine. What do you mean by that? Here's a link to a very good automatic to manual swap article. You'll be doing the thing in reverse of course. Your engine and your automatic transmission will need computers to control them. Your mention of an engine swap makes all of that pretty unclear. Your transmission needs to be paired with your engine and the computer.

auto-to-manual-writeup-5-speed-conversion-t181139.html

Thanks Central, yeah so its a 90 240sx with the stock Ka24e in it. I planned on doing an engine/tranny swap in the vehicle to begin with. Was initially going to do an RB swap, however (mentioned in a really old post) my wife has a very rare condition and cant physically ride in a manual so ive been considering other options such as maybe a an automatic vq swap, or something else, the engine isnt set in stone yet because i wasnt going to waste my time if it was somethign that is just completely undoable. Ive helped with an auto to manual conversion before, but anytime ive looked in the reverse it was always just buy a new car but noone ever said why. Being this 240 is sentimental and im keeping it for that reason id rather modify it how i want even if it does cost more then just buying a new one that would be easier. This is not going to be your typical sports car, i plan on putting in extra sound dampening etc, nice audio, it will be more of a cruiser/luxury style 240 when im done with it.

Post by **240TKE128** » Wed Dec 27, 2017 12:24 pm

By the way, So i was able to confirm i could still get my hands on one, but the swap would be an

RB26DETT with RB25 Auto Trans (if we move out of the mountains)

If we stay in the mountains to allow for year round driving i will be taking on the full ordeal of customization and fabrications to do

RB26DETT with AWD Auto Trans

Post by **centralcoaster33** » Thu Dec 28, 2017 1:10 pm

Well, imho, part of the sentimental value of a car is how it feels and drives, not just the VIN or pink slip. I don't see an AWD project really keeping the same life of the car, but perhaps with you that will be different. I've seen one S13 with the skyline drivetrain stuffed in. I've seen a kit for the S14 with RB26. That's about it.

As far as computers and transmissions go, the controls for the automatic transmission will be inside of the ECU for the engine. So, whatever engine you go with, you'll need the automatic ECU for that particular year/ model. That might limit the options for which automatic transmissions will work with the computer.

Post by **240TKE128** » Thu Dec 28, 2017 1:37 pm

centralcoaster33 wrote: ↑
Thu Dec 28, 2017 1:10 pm
Well, imho, part of the sentimental value of a car is how it feels and drives, not just the VIN or pink slip. I don't see an AWD project really keeping the same life of the car, but perhaps with you that will be different. I've seen one S13 with the skyline drivetrain stuffed in. I've seen a kit for the S14 with RB26. That's about it.

As far as computers and transmissions go, the controls for the automatic transmission will be inside of the ECU for the engine. So, whatever engine you go with, you'll need the automatic ECU for that particular year/ model. That might limit the options for which automatic transmissions will work with the computer.

K perfect, so my understanding that as long as the engine ecu and transmission match is spot on, I was always curious why people freaked out anytime you mentioned it.

It may not be a factor anymore though, we got some bad news health wise for her so i probably wont be able to get it running again before it happens.

Thank you everyone for your responses.

Post by **centralcoaster33** » Thu Dec 28, 2017 5:35 pm

Ah, I recall now. You and Kat. MS or devics or something. Hence the on and off with the car... So, you want to smooth out the ride in the 240sx for Kat right? Is this for regular transportation or for fun cruising? I mean, is the Subaru and option for transporting her for non-fun rides? And what kind of fun rides would the 240sx with a smoother transmission be for? What does she get out of a ride (music, company, smokin' bowls, wind in the hair, exploring, scenery...)? I'm trying to wrap my head around the issue and come up with solutions.

Post by **240TKE128** » Fri Dec 29, 2017 8:28 am

centralcoaster33 wrote: ↑
Thu Dec 28, 2017 5:35 pm
Ah, I recall now. You and Kat. MS or devics or something. Hence the on and off with the car... So, you want to smooth out the ride in the 240sx for Kat right? Is this for regular transportation or for fun cruising? I mean, is the Subaru and option for transporting her for non-fun rides? And what kind of fun rides would the 240sx with a smoother transmission be for? What does she get out of a ride (music, company, smokin' bowls, wind in the hair, exploring, scenery...)? I'm trying to wrap my head around the issue and come up with solutions.

Hey Central,

Thats right, (little things like planning etc help keep me sane when she is not doing well) we are not sure how long she has left. Yeah the Subby is for regular transport and day to day, the 240sx is for enjoyment, when we were first dating we were to poor for anything so we just drove around in the 240 all the time. We live in the mountains near the dragon tail infact.

At this point the car is starting to rot away so im having to do alot before i feel it will be safe to drive, plus its now infested with mice, ants, spiders, etc from being parked in a yard(no place to store it properly. Fuel lines have rotted, etc, ill be honest once i finish a tear down i may have to scrap the whole car im not sure even with m y self taught and stubborn a** i can fix all the rust i see with my eyes let alone stuff i havnt seen(frame started crumbling when i tried to jack it up the other day.

Post by **PapaSmurf2k3** » Fri Dec 29, 2017 10:18 am

Yeah converting that into an AWD RB car is a pipe dream. I wouldn't even attempt to take it on. It would take you an eternity to complete.

To answer your original question, the best way to swap from a manual to an auto would be to just sell the manual and buy an auto car, but if you're hell bent on keeping the one you've got, you could just buy the auto car, and swap the engine, trans, wiring harnesses,ECM, TCM, interior, pedals, radiator, and ATF cooling lines over from the one car to the other.

Post by **240TKE128** » Fri Dec 29, 2017 10:27 am

PapaSmurf2k3 wrote: ↑
Fri Dec 29, 2017 10:18 am
Yeah converting that into an AWD RB car is a pipe dream. I wouldn't even attempt to take it on. It would take you an eternity to complete.

To answer your original question, the best way to swap from a manual to an auto would be to just sell the manual and buy an auto car, but if you're hell bent on keeping the one you've got, you could just buy the auto car, and swap the engine, trans, wiring harnesses,ECM, TCM, interior, pedals, radiator, and ATF cooling lines over from the one car to the other.

Thanks Papa yeah i know doing the AWD will be a complete pain for years, i was also considering keeping it RWD since we may not be able to stay in the mountains due to her illness. but i figured the transmission part would be the same regardless of which conversion i did. i figured it was as "simple" as making sure you had all the pieces and then just doing it, the key thing is i was planning on doing an engine swap anyway so i figured since id have to swap trans and everything else anyway the only real difference would be the ATF cooling parts. Glad that i was atleast right on that one.

Post by **PapaSmurf2k3** » Fri Dec 29, 2017 11:06 am

Oh yeah, driveshaft will be different as well.
And don't forget about the chassis harness. I'm pretty sure that will be different as well, seeing as how you'll need to actually plug the TCM into something.

Post by **blkvrtswp** » Sun Dec 31, 2017 8:20 am

The problem is that on the 240sx and the KA/CA/SR/RB engines, the automatic computer is NOT located on the engine harness. It is on the cabin chassis harness, which you usually are not going to have on a swap engine set. This computer controls the shifting logic.

Yes, the main ECU will have to be an auto one (for TPS WOT downshift & higher idle), but that is not the whole picture. If you have a front clip, you may get all the computers and harnesses you need. The wiring will be very difficult for any engine set not from the S13.

ONCE long long ago, I installed an auto S13 SR20DET in an auto S13 240sx. Was no problem at all to get working, very little wiring aside from the basic swap wiring but again - we had the full clip w/ harness and computers and it was not a chassis change. IIRC the SR auto ECU plugged into the KA chassis harness.

I personally did not like it - it felt fragile to me, not sure why - never got a chance to see if it would hold up because unfortunately the buyer of the car installed a manual boost controller the FIRST NIGHT HE HAD IT and blew the compression on 2 cyls 10 days after the build was finished.

As for AWD S13 - that's a 10K plus project there (if lucky and skilled), not including the engine/trans set. Would be awesome, it has been done a few times.

Post by **240TKE128** » Mon Jan 01, 2018 11:11 am

blkvrtswp wrote: ↑
Sun Dec 31, 2017 8:20 am
The problem is that on the 240sx and the KA/CA/SR/RB engines, the automatic computer is NOT located on the engine harness. It is on the cabin chassis harness, which you usually are not going to have on a swap engine set. This computer controls the shifting logic.

Yes, the main ECU will have to be an auto one (for TPS WOT downshift & higher idle), but that is not the whole picture. If you have a front clip, you may get all the computers and harnesses you need. The wiring will be very difficult for any engine set not from the S13.

ONCE long long ago, I installed an auto S13 SR20DET in an auto S13 240sx. Was no problem at all to get working, very little wiring aside from the basic swap wiring but again - we had the full clip w/ harness and computers and it was not a chassis change. IIRC the SR auto ECU plugged into the KA chassis harness.

I personally did not like it - it felt fragile to me, not sure why - never got a chance to see if it would hold up because unfortunately the buyer of the car installed a manual boost controller the FIRST NIGHT HE HAD IT and blew the compression on 2 cyls 10 days after the build was finished.

As for AWD S13 - that's a 10K plus project there (if lucky and skilled), not including the engine/trans set. Would be awesome, it has been done a few times.

Blk thank you that is the most detailed answer ive ever seen online about the topic, Price wise isnt the concern for me as if im going to do something im going to do it and if it takes longer so be it. but i will probably have to swap the chassis harness out as well as the car got flooded. so im thinking w hats going to be best is to take it down to bare metal inside and out, fixe the rust etc, and start fresh with new and/or cleaned ducting, wires, etc..

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