briankk Posted July 6, 2017 Share Posted July 6, 2017 In my endless quest for a replacement trans for my '94 SVX, I've corralled a '98 Impreza trans, TZ102Z5AA-GN., and all the downstream 4.11 gearing stuff. Suitable for SVX, or no? Quote Link to comment Share on other sites More sharing options...
golucky66 Posted July 6, 2017 Share Posted July 6, 2017 Automatic? I'd think you'd have compatibility issues with the svx being 94' non obd 2 and the impreza transmission being obd2... Others will chime in about it I'm sure, but that's the jist I get about mix and matching non obd and obd. Quote Link to comment Share on other sites More sharing options...
matt167 Posted July 6, 2017 Share Posted July 6, 2017 OBD-1 vs OBD-2 has nothing to do with it. The transmission differences came in 1999. Transmissions to 1998 are compatible between OBD-1 and OBD-2. They are " Phase 1" transmissions, you cannot use "Phase 2" transmissions which started in 1999. Phase 2 trans can be identified by the external filter on the drivers side of the trans 1 Quote Link to comment Share on other sites More sharing options...
briankk Posted July 6, 2017 Author Share Posted July 6, 2017 Automatic? I'd think you'd have compatibility issues with the svx being 94' non obd 2 and the impreza transmission being obd2... Others will chime in about it I'm sure, but that's the jist I get about mix and matching non obd and obd. '98 Impreza is OBD 1. And now you mention it, I forgot to get the TCU that was supposed to come with it. I think it's an early WRX box, will want different shift points than SVX. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted July 6, 2017 Share Posted July 6, 2017 '98 Impreza is OBD 1. And now you mention it, I forgot to get the TCU that was supposed to come with it. I think it's an early WRX box, will want different shift points than SVX.No it isn't. Every car sold in the US had to be OBD II in '96. Subaru did not sell a WRX in North America until 2002. You have to use the SVX TCU. Quote Link to comment Share on other sites More sharing options...
wtdash Posted July 6, 2017 Share Posted July 6, 2017 +1(000) Quote Link to comment Share on other sites More sharing options...
briankk Posted July 6, 2017 Author Share Posted July 6, 2017 No it isn't. Every car sold in the US had to be OBD II in '96. Subaru did not sell a WRX in North America until 2002. You have to use the SVX TCU. Well, the junkyard paperwork listed the car this trans and TCu came out of as a '98 Impreza, and it had a phase 1 trans, early WRX brakes on all corners (black painted caliper with "Subaru" cast in in relief, and an EJ22 engine. When I saw the WRX brakes, I wanted to see the engine to see if it was a turbo 2 litre, on the remote chance junkyard didn't know the difference. They did. I know the difference between a phase 1 and phase 2 4EAT, this is a phase 1 transmission, I got the TCU thinking that this trans had used those shift points all its life, didn't want to upset its delicate innards by imposing SVX shift points. OBD2 came along at about the same time as the phase 2 trans, I think of them interchangeably, FWIW. Quote Link to comment Share on other sites More sharing options...
wtdash Posted July 6, 2017 Share Posted July 6, 2017 (edited) OBD2 came along at about the same time as the phase 2 trans, I think of them interchangeably, FWIW. No offense, but this is also incorrect. 1996 was OBD2 (1995 for some Subaru models). The phase 2 was a '99+ for all the 4EATs. Although years may be 'the same time' in your book, I don't think most of USMB'ers would agree....there are just too many differences. Td Edited July 6, 2017 by wtdash Quote Link to comment Share on other sites More sharing options...
briankk Posted July 7, 2017 Author Share Posted July 7, 2017 I am in California, so must comply w/California law, which says that I have to use a phase 1 trans in my '94 SVX. So, I'm not much interested the the dates involved, but with whether or not I have a phase 1 trans, which I have. Unimportant to me what year, can only tell you what the written documentation says, and it says the car is a '98 Impreza, not much interested in whether it's a '98 Impreza or a ball of peanut butter, so long as the phase 1 trans will bolt into and work in my SVX. This trans is a TZ102ZA5AA-GN, if you Google that trans number you will see that there seem to be a lot of folk who believe its OEM in a '98 Impreza... Quote Link to comment Share on other sites More sharing options...
Subaru Scott Posted July 7, 2017 Share Posted July 7, 2017 You are still confusing phase 1 with OBD 1. When we say phase 1, we are speaking of the transmission. When we say OBD 1, we are speaking of the on board diagnostic system. Your 94 SVX is OBD 1 with a phase 1 4EAT transmission. The 98 Impreza is OBD 2 with a phase 1 4EAT transmission. You MUST use the SVX TCM. The transmission DOES NOT CARE AT ALL ABOUT SHIFT POINTS. Quote Link to comment Share on other sites More sharing options...
briankk Posted July 7, 2017 Author Share Posted July 7, 2017 You are still confusing phase 1 with OBD 1. When we say phase 1, we are speaking of the transmission. When we say OBD 1, we are speaking of the on board diagnostic system. Your 94 SVX is OBD 1 with a phase 1 4EAT transmission. The 98 Impreza is OBD 2 with a phase 1 4EAT transmission. You MUST use the SVX TCM. The transmission DOES NOT CARE AT ALL ABOUT SHIFT POINTS. So, you are telling me I have a phase 1 trans that talks OBD2? Seems unlikely.. Phase 2 box has more solenoids than phase 1... It may seem I don't understand the difference between OBD1 and OBD2. But I do understand. I can't legally (or mechanically) run a phase 2 trans with mt '94 SVX. I know that. It's therefore of no interest to me what phase 2 or phase 2A trans do, or when they were made, or whether they have cool tats, or anything at all about them. What I am interested in is whether anybody know of any actual internal differences between various phase 1 transmissions. Specifically, what is the difference between the stock SVX box(TZ102ZM1AA-KP), and the trans I intent to replace it with (TZ102ZA5AA-GN). Both are phase 1 boxes. So far, no joy.. OK, TCU has nothing to do with shift points. So what does it do? I already know I can unplug the thing without having a perceptible effect on the way the car drives. I reckoned that since the GN box is from a car not an SVX, its torque converter stall speed and shift points would be different from those in an SVX. Wrong? What does the TCU do? Educate me... Quote Link to comment Share on other sites More sharing options...
Subaru Scott Posted July 7, 2017 Share Posted July 7, 2017 OBD changed in 95-96, Transmissions changed in 98-99. Two separate changes. Between those changes, all cars were OBD 2 with phase 1 transmissions. There were some small changes in the transmissions, but nothing that will throw a code or cause a problem. All you need to be concerned with is the final drive ratio. Whatever you're unplugging, (probably the cruise control unit) it is not the TCU, which has everything to do with shift points, but it needs to match the vehicles OBD. Quote Link to comment Share on other sites More sharing options...
briankk Posted July 7, 2017 Author Share Posted July 7, 2017 SVX has 3.54 final drive, so along w/the trans, I bought the rear end, axles and TCU all 4.11 stuff I know that Subaru improved the 4EAT as they went along, is why I bought a '98 phase one, thinking it must be the strongest possible phase 1 box. But is it? It came off an EJ22 engine, going on an EG33 that has near double the power and torque of the 2.2 engine. I fret about this some.. The thing I unplugged was the 13 pin shell connector on top if the transmission. If that didn't disconnect the TCU, I do wonder what does? OK, in post #10 Subaru Scott says TCU doesn't affect shift points, in post #12 that it does... I'm confused too.. Quote Link to comment Share on other sites More sharing options...
Subaru Scott Posted July 7, 2017 Share Posted July 7, 2017 I said: the TRANSMISSION DOES NOT CARE AT ALL ABOUT SHIFT POINTS. Quote Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 7, 2017 Share Posted July 7, 2017 The trans doesn't "talk" either OBD-1 or OBD-2. It speaks ONLY SSM. The OBD-1/2 is in reference to the ENGINE COMPUTER ONLY. It has absolutely nothing to do with the trans. The OBD-2 is a LIMITED, ADDITIONAL, MANDATED interface that was globbed on top of the existing Subaru Select Monitor (SSM) architecture. Only the ECU speaks this additional language if it is requested to do so by a compliant scan tool. None of this has anything whatsoever to do with the trans. It is phase 1. WRX brakes can be installed on any Subaru. I have them on my 91 Legacy. GD Quote Link to comment Share on other sites More sharing options...
briankk Posted July 7, 2017 Author Share Posted July 7, 2017 OK. Googled "What does TCU do, in 4EAT?", got a lot of info. Seems to me SSM is native built in control program, is modified by various TCUs according to various criteria in various Subarus. GitHub seems to some useful programs read and adjust these things.. WRX brakes cannot be bolted onto SVX, brackets wrong. Can be bolted onto my '96 Brighton, but would require 16" wheels to clear the caliper, then new tires to fit 16" wheels, not gonna happen anytime soon. Darn it. Abandoning OBD discussion, it's irrelevant to what I'm trying to do... Quote Link to comment Share on other sites More sharing options...
idosubaru Posted July 7, 2017 Share Posted July 7, 2017 This is really simple: 1. you did the right thing and got a Phase I transmission and matching final drive ratio rear differential. 2. install it and drive it. 3. Whether it's possible or not aside - there's no need to swap TCU's - the transmission is just a mechanical device, if routines execute X% sooner, later, slower, or faster than before - it's still doing the same exact routine tasks all transmissions do. to be worried about internals is akin to worrying if different altitude, climate, geography, changing daily driver use, more hills, different weight, etc will cause different wear or stress... it's perfectly capable of handling it, that's what they do and that doesn't change over time. XRT tunes Subaru TCU's if you wanted to dial it in a little sharper or make any changes, they may be able to help: http://xtremeracingtuning.com/tuning-services/ You could ask and talk more specifically about what you're asking. Making comments that aren't true confuses the discussion, like this: OBD2 came along at about the same time as the phase 2 trans, I think of them interchangeably, FWIW. Quote Link to comment Share on other sites More sharing options...
briankk Posted July 7, 2017 Author Share Posted July 7, 2017 Thanks for the tip on the TCU tuner. It's my understanding that one of the problems in the phase 1 4EAT (4-speed. Electronic, Automatic Transmission) is too low pressure in hydraulic circuit that engages the torque converter lockup, which is inclined to "hunt" at less than freeway speeds, and due to low application pressure, eventually slip, causing wear. Solution would seem to be to raise pressure in that circuit, was going to see if GitHub tuner allows that without having to refer to outside tuner.. I've got a paper somewhere describing the various upgrades and continuous improvements in the 4EAT, that involve various internal mods, am trying to find which of these might be retroactively applied to the phase 1 trans, such as for instance better clutch material, etc. A lot (most?) phase 2 stuff cannot be dragged back into phase 1 boxes, but I reckon it's worth a look. Most important mod to phase 1 is external filter and ATF cooler, IMHO. Precise day and date of OBD 2 implementation is a bit slippery in Soobs, as various models changed a various times. My only interest is whether or not theres is a external oil filter, denoting a trans too new for my use, and then latest possible phase 1 box, for most upgrades in that series. Quote Link to comment Share on other sites More sharing options...
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