Everybody seems to know what manual trannies can be swapped on a g2… but…
What auto trannies can be used, from what cars/years? I’d like to do a B20 swap, but I doubt the original tranny can handle the torque (even if it could, it’s up there in miles), and really don’t want to go through the hassle of a auto -> man swap.
I don’t know the complete answer to your question because it is more complex than swapping a 5 speed tranny. While a 94+ automatic tranny will bolt up to a G2 engine, there is a big difference between them. The TCMs are different, the gear shift mechanisms are different. When you swap an automatic, there is much to consider. I am swapping a JDM B18C automatic into my 92 Integra. It is even more of a challenge because the JDM auto tranny equipped vehicles did not use a TCM. All the tranny functions are controlled by the ECU. The ECU has an extra plug for this. I still have been unable to find a pinout diagram for the ECU. So I recommend staying within the same generation of Teg to minimize the issues.
Hey OldGuy can you keep us updated on the engine and tranny swap? I am in need of a new tranny and am considering putting in a JDM or 94+ automatic in my 92 LS.
Sure. I have been keeping a diary and have taken a whole bunch of digital pictures to accompany the diary. Once the weather turns crappy here, which won’t be too much longer, my car is going into storage. The old engine/tranny is out. I have been spending time restoring the front suspension and engine compartment etc. I am proud to say I now have no rust. All the components have been restored to like new condition. I’ll explain that more once I get the diary up on the site. The B18C engine is done. I stripped it down, except for the head and internals and checked it all out including a leak down test on all of the cylinders. I have the harness removed and labelled. I put a new fuel rail and adjustable pressure regulator on it while I was at it. Anyway, I’ll check with the site moderator to determine the best way to publish it. The bad news is that I won’t be doing the real work until next spring. I still have more research to do on the tranny and JDM ECU. I want this to work right the first time.
Just to add to my last post, the main issues, including the JDM differences, I have discovered swapping a G3 automatic into a G2 are:
I got the engine and transmission together as a package along with an uncut harness and two ECUs. I have been able to locate one source who has done considerable work on JDM swaps who says that the P72 Automatic has different gearing than the LS automatic. He is the first person to tell me that. Several posts I have read on this site and others claim that the JDM automatic is the same as the LS tranny in North America. For me, the jury is still out. It does make sense that the gearing would be different considering the difference in the two engines and the fact that a P72 automatic was a standard production car in Japan for a few years. I have a friend going home to Hong Kong in December. He has a brother who works for Honda over there. I am providing a bunch of questions including a request for a pinout diagram for the ECU. I hope to get more information from him or at least a contact.
I found some information for you Oldguy. Here are two links that talk about the auto ecu. One site is for a harness. Click on the custom button and read at the bottom. This might be what you need.The other is from a forum about a automatic swap.
g2 Auto - 4 shift solenoids
B16A Auto - 4 shift solenoids
94+ LS Auto - 2 shift solenoids
JDM 94+ GSR - i fergot how many but I’m guessing OldGuy can fill us in.
G3 Torque Converter is better than the G2. G3 tranny sucks ass it doesn’t pull like a G2. When you or someone you know shift their G3 auto to D3. The car just doesn’t pull it actually feel like the car is struggling. My friend decided it get a better pull on 2 than D3. But then I told him it’s bad to bring it down to 2 or even 1. Those lower gears are only good if you climbing up hill. Like in Yorba Linda or Diamond Bar.
upgrade kit in a g2 tranny with g3 torque converter?
Thanks for the attempts to help. I checked out the forum that was listed in the above post. I am afraid that I disagree with the 4th plug assessment on that forum or it could be a totally different situation. The guy talks about a 4th plug on the Prelude 4 wheel steering ECU and says it is an orphan. Not many were made. He says the fourth plug is the “B” plug. The guy talking about OBD2 also says the “B” plug. In my case the extra plug is the “C” plug. I have attached a picture of two OBD1 ECUs. One has three and one has four connectors. You all will recognize the three connector model. The connectors are identified left to right as “A”, “B”, “D” on the three connector ECU. The fourth connector on the automatic ECU is the small one and is the “C” connector. You can see that the rest are the same as on the 3 connector ECU. OBD2 connectors are a different size and shape and Yes on the OBD2 ECU, the “B” connector is blank on 5 speed tranny ECUs and may be blank on all ECUs. I am not sure. The other erroneous statement relates to the Transmission Control Module (TCM). It is true that in North America all automatic Integras have a TCM that talks to the ECU to get various sensor parameters and provides commands to the shift and lockup solenoids of the automatic transmission. The G2 and G3 TCMs are actually quite different. However, in Japan, there is no TCM in the automatic integra. The functions are accomplished in the main ECU. If you could see inside the JDM automatic ECU you would see that it is very much more complex than the standard ECU. So, I still don’t have the answer but I have wiring diagrams for both G2 and G3 integras, including the ECUs and TCMs so I will probably go with a trial and error situation starting with the existing G2 wiring and re-routing the TCM outputs to the fourth plug and go from there. I will use the JDM harness pieces wherever necessary to adapt it to the G2 car. I am making the assumption that the ECU to TCM connections found on North American cars are not necessary. All that would be done internally in the JDM ECU. Comments?
By the way I did absorb the suggestions about putting the G3 torque converter into the G2 tranny. I will take a look at that. The problem is that the G3 tranny, which is what is hooked up to the JDM B18C functions differently and has two extra sensors in the transmission. I don’t know if the G2 tranny would work with the 4 plug ECU. Lots of fun.
Interesting… I’ll probably will be doing a setup similar to this pretty soon. I have the g2 auto tranny, g3 torque converter, and g3 flex-plate [dunno if it does any good]. Then I want to have a chance to do it on a G3 where I replace the auto tranny with a G2 auto.
I was thinking of using a TCM off of the 97 prelude or just plain out mess around with the DA TCM to see if i can convert the cruise control buttons to use it as a paddle shift just like the newer cars.
I am having difficulty knowing who to believe on the various forums where I have discussed this. I was told by a couple of sources that the G3 auto tranny is stronger and that the JDM version on the B18C had different gears. I had read the opposite also and then subsequently found a spec sheet on the Honda Japan web site that confirmed that the auto tranny gearing is identical to the North American G3 gearing. The G2 tranny pulls better because its overall gear ratios are lower (not by much) than the G3. The only gear in which the G2 is not lower is 1st gear, again not by much. I have the ratios if anyone wants to see them side by side. Let me know.
The one big advantage of the G3 tranny is its ability to cycle through the gears manually. The G3 has a 1st, 2nd, D3, and D4 on the shift selector. The G2 does not have a 1st gear on the shift selector. The book says that 1st and 2nd are for going down hills and getting a slow start etc. They can also be used in a manual mode just like the paddle shift of todays cars. I don’t know if there is any ECU limitation in any of the gears.
You might want to read up a bit more on the G3 versus G2 tranny. I think overall that the G3 tranny is the better one. The physical setup of mounts in the car are different along with the function and electrical differences. I don’t think you gain enough (if anything) to make it worthwhile swapping in a G3 tranny into a G2 car. Honda does not usually go backwards in quality and function. If you did do it, you would have to change mounts, TCM, shift selector, cables and ECU to make it work properly. There is also a throttle cable extension connected to the G3 tranny that is not on the G2.
I deal with these issues on a risk versus gain assessment. How much do I risk versus what I get out of the result. I do all the work myself so I have to be confident that what I plan can actually be done by me and has a good chance of working properly. I also don’t change too many things at once so that if it does not work, you can trouble shoot the problems more easily.
This thread has made me think a bit more about whether to stay with my G2 tranny. It might be less risky. I will let you know.
I have the auto tranny specs for JDM G2 and G3. I have notice that you can shift to those gears on G3 but it feels like it wasn’t made to do that. You can shift very freely from D4 to D3 and back. But not on 1st and 2nd.
I wanted where it shift with electronics/circuitry/wires rather than shifting it manually on the shifter mechanism. Level 10 actually makes this except it only good for americano car.
I’m not trying to fit a G3 tranny onto a G2. I’m just putting in the G3 torque converter and flex-plate. That’s about it. I might even go with a JDM G2 auto tranny.
What you said about it having a throttle extension. Maybe it be a good idea to get the throttle body off of a auto G3 and use that. You will eliminate that dashpot on our stock g2 throttle body and have some sensor off the firewall.
I misunderstood you. Sorry. Actually I do have a G3 TB because this is a B18C swap into my G2. I am concerned about the functions of the tranny. It would be easiest for me to hook up the G2 auto tranny to the VTEC engine, and use the G2 wiring harness with the addition of the VTEC functions. That would be the cleanest startpoint. Then I would try to migrate the TCM functions over to the 4th plug on the ECU. That way I can keep my shifter, etc. The potential problem is the difference in the way that the two trannys function. The G3 has two tranny shaft speed sensors that feed the computer. I don’t know the implication on the 4 plug ECU if those sensors are not present. I would bet it would set a code or two. Then I won’t know what the codes mean. I don’t know if this JDM ECU has amalgamated the OBD1 engine codes with the TCM codes on the same box. Last summer I hooked up the 4 plug ECU in my stock G2 but only connected the three plugs on the harness. It started but ran rough at idle. It had good power and still would shift, except for the S3 to S4 shift. It didn’t recognize that. However, when I shifted manually to Drive, it shifted into high gear and it did lock up. Thats all because the G2 TCM was still in the loop. I got only engine codes set for the VTEC stuff (not surprised) and the O2 sensor, which was a surprise. It indicated the wiring for the stock G2 is not quite the same on the three existing plugs. That probably also explains why the idle was rough. Having said all of this, I still feel that maybe the G2 tranny with the G3 torque converter is the safest option until I figure out how the 4 plug bugger works.
What makes the G3 torque converter better? Is this just “hear say” or is there evidence that it is better? I to am thinking of getting a JDM auto tranny off of a 90-93 Integra XSi. Anyone know if the gears really are lower? I think putting a G3 tranny in our cars are not worth it after reading this post and others.
When I was comparing the torque converter with a usdm g2 and a g3 last year. They look exactly the same except the weld spots area. I have some information a few years back saying the internal of the g3 is better than the g2. I guess it has better lock-up mechanism/plates.
I probably might pull up some of my bookmarks or saved file somewhere. If I can’t find the information to back it up. I’ll just be a guinea pig then.
You are correct. I made a mistake on the plug names. The plug that is the 4WS on the H22a JDM ECU is the “C” Plug. On the OBD2a ecus, the B plus is only used on the Automatic chassis.
You have a good challenge on your hands, but an obtainable one. When I first did the auto to auto accord-h22a conversion, everyone said it was not do-able. But I have finished it a while ago and it was a huge success. I would like to offer my assistance if you want it. I do not have alot of knowledege on the JDM G3 auto setups, but I can source some stuff no problem. Do you have the JDM manuals for that setup? Have you considered running the USDM ECU/TCM? Let me know if I can help.
Also, here is the JDM H22a Auto ECU with 4WS and various images.
You think that can be implement in a Integra? Using 88-91 Prelude components?
Welcome Aboard “OBD Harnesses”. Any help you can offer would be great. I can only speak for myself but my biggest headache is obtaining the wiring and/or pinout diagrams for my JDM ECU. It is a “P72-901” automatic ECU, the one pictured above in one of my earlier posts. I have searched everywhere I know including buddies of mine in Hong Kong and Malaysia. I am told that it was exclusively a Japanese market product. They did not export it anywhere. I have considered the G3 TCM but the issue of an automatic tranny and a VTEC engine can only be resolved by using a JDM ECU unless I want to shift the automatic manually and not get full function from it. There was one of our members who, I think, said his buddy just used the P72 manual ECU and shifted the auto tranny manually. That would work probably but I doubt that the converter would lock up. So its a compromise that I am still studying. I would like to use the JDM ECU. I think that would get me the best result. Do you have or do you know where I can get a diagram of pinouts. If you provide these services as a “profession” and you are looking to get paid, then please contact me by e-mail and let me know what you offer and how you can help me get this up and running. I have two of these ECUs, both identical, so some experimentation is possible.
4WS in 1988-1991 was mechanical. You can always try, but Prelude and Civic/Integra chassis are very different.
Regarding the JDM AT swap, I did a AT to MT swap in my 1995 Legend. It also uses the integrated TCU within the ECU. I bet that the wire colors are the same, if not the pinout, between the Integra ECU and the Legend ECU. Honda swaps pin locations, but the colors are generally the same. It is worth a try, maybe you can at least label the wires you have.