T0MCAT Posted October 24, 2010 Share Posted October 24, 2010 I have 3 speed FWD auto tranny in my 1985 car and thinking about swap it to the newer 4 spd tranny. I know about 25 splines and ECU on the 4 spd tranny, it is not a big problem for me. Also i hear somewhere that subaru from 1988 have bigger transmission tunnel, is it right? Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted October 24, 2010 Share Posted October 24, 2010 The TCU requires some inputs from the Fuel Injection ECU for correct operation IIRC. So if you have a carb engine that might be a problem. I beleive the 4EAT's are larger and the car's did come with a bit larger tunnel, yes. GD Quote Link to comment Share on other sites More sharing options...
idosubaru Posted October 25, 2010 Share Posted October 25, 2010 some spacers like used in lifting the vehicle might bump it enough to give you clearance? an inch or two would likely suffice...or an inch or two with some hammering too Quote Link to comment Share on other sites More sharing options...
T0MCAT Posted October 25, 2010 Author Share Posted October 25, 2010 (edited) Great thanks to all who answer! May be i will buy a newer loyale or, even, legacy, and will swap from donor not only transmission but engine, tranny, ECU, TCU, etc... That's why a smaller tunnel can be only one real issue for me. I'm digg into internet and not find any mention about another body used from 1988. Chassis models also not changed. I know earlier (before 84) models have different tunnel, but not sure about difference between 84 and 88 cars.It seems a bit illogically from point of unification I think. Also bigger tunnel can change some in salon or dashboard. Can anyone have some pictures of 3AT and 4AT transmissions, or better dimensions? Or experience of swap newer tranny into older body? Edited October 25, 2010 by T0MCAT Quote Link to comment Share on other sites More sharing options...
eulogious Posted October 26, 2010 Share Posted October 26, 2010 As long as you use a phase 1 4EAT, all it needs is an RPM signal from the ecu, or whatever, that's it. It just needs that RPM signal. It's basically a completely separate subsystem. That changed with ODBII of course, but the early 4EAT were super simple. You will also need to make sure you get some of the other sensors it needs though as well. Like the TPS, the 2 VSS', those are the two off the top of my head that are important for it to work. This info is not feed from the ECU, it's taken right from the sensor it's self, so just make sure you get the wiring diagrams and make sure all the sensors are hooked up to the TCU. It requires more sensors to work than the 3at because of the computer that the 4EAT has, so some of those things you might not have... Is your car carbed or SPFI? If you don't have SPFI, then you are kinda screwed, you need the TPS. Might be a good time to do the SPFI swap if you motor is carbed... Another thing you are going to have to look out for is to make sure the TCU and the trans match up, same with the rear diff. The 4EAT changed final drive ratio and what not throughout the years and different models it was in, so make sure you grab the TCU and the rear diff from the donor car, that way you know it will work correctly. If they don't all match up, the TCU will be rather sad. You will like the upgrade. They are good trannies. This swap will require a little bit more work, but it is doable. If I was going to do the swap, I would go with an EJ donor, not an EA. So grab an early legacy (90-94) 4EAT trans, the TCU, and the rear diff. Those have the better computer and the better ratio's, and there are slightly different but better things done with the actual trans when compared to the EA version of the 4EAT. Nothing big, but better for reliability. Keep us posted man! Quote Link to comment Share on other sites More sharing options...
Gloyale Posted October 26, 2010 Share Posted October 26, 2010 As long as you use a phase 1 4EAT, all it needs is an RPM signal from the ecu, or whatever, that's it. It just needs that RPM signal. It's basically a completely separate subsystem. That changed with ODBII of course, but the early 4EAT were super simple. You will also need to make sure you get some of the other sensors it needs though as well. Like the TPS, the 2 VSS', those are the two off the top of my head that are important for it to work. This info is not feed from the ECU, it's taken right from the sensor it's self, so just make sure you get the wiring diagrams and make sure all the sensors are hooked up to the TCU. It requires more sensors to work than the 3at because of the computer that the 4EAT has, so some of those things you might not have... Is your car carbed or SPFI? If you don't have SPFI, then you are kinda screwed, you need the TPS. Might be a good time to do the SPFI swap if you motor is carbed... Another thing you are going to have to look out for is to make sure the TCU and the trans match up, same with the rear diff. The 4EAT changed final drive ratio and what not throughout the years and different models it was in, so make sure you grab the TCU and the rear diff from the donor car, that way you know it will work correctly. If they don't all match up, the TCU will be rather sad. You will like the upgrade. They are good trannies. This swap will require a little bit more work, but it is doable. If I was going to do the swap, I would go with an EJ donor, not an EA. So grab an early legacy (90-94) 4EAT trans, the TCU, and the rear diff. Those have the better computer and the better ratio's, and there are slightly different but better things done with the actual trans when compared to the EA version of the 4EAT. Nothing big, but better for reliability. Keep us posted man! It will need. Tach signal VSS signal TPS (Throttle Sensor) signal. (this is the tough one) The carbed car won't have a TPS. YOu could rig one from a MPFI GL or EJ car (use one that matches the TCU you pick) onto the throttle shaft of the carb. He can run a 3.9 trans off a 3.7 computer(personally done this and it worked fine) I am also guessing he can run 4.11 trans off 3.9 computer. The difference is still small. But if the difference is too far off (4.11 off 3.7 computer, 3.9 off 4.44 computer, etc...) it will cause problems. Quote Link to comment Share on other sites More sharing options...
T0MCAT Posted October 26, 2010 Author Share Posted October 26, 2010 My car is carbed. Firstly i think swap only transmission , thats why i so interested about tunnel. But after all this answers may be better find first gen legacy and swap engine, "electronic brains" and transmission? Now my car is FWD, so i can search the FWD legacy or convert my car to 4WD. Guys, big thanks for your answers! But now i have more questions about it. I was think is relatively simply, and main issue is the probably smaller tunnel. But now i see is more complexity. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.