Numbchux

I would bet externally interchangeable. Definitely different internals, but I suspect due to different assist amounts. I know the pumps have different volume and pressure specs. I'd try it. YMMV

Well, it's more complicated than I implied. The current part number, 11044AA610, is steel as far as I can tell. There are 3 older part numbers that were replaced by the 610, I am much less clear what the material of those were, either from my memory or service manuals. So the factory installed ones might have been a different material.

It is here, too. But getting another rust free shell is no small feat in this part of the world. IIRC he travelled to California for this one. Not to mention the modifications already done to this one. That looks pretty nasty, but all ahead of the suspension mounts, so it doesn't need to be mm perfect.

Yep, Subaru shows 879996 as the Transmission serial and 424274 for the engine (IIRC stamped into the engine block next to the starter).

The 4EATs are not picky about what fluid to use. You can buy Dex III, it's usually labeled Dex/Merc (Dexron/Mercon). That's the cheap conventional stuff, works great, meets all the specifications. I buy 2.5g house brand jugs of it at Fleet Farm. All Dexrons are backwards compatible. So you can use those. Most will be synthetic (certainly anything you can find new) Subaru officially superseded to HP. So anything that meets Subaru HP will also work. This will all be synthetic. This is what we carry and use (I work at a Subaru dealership) I honestly think the change to HP was just to use a synthetic so they can extend suggested service intervals and/or in an attempt to reduce resistance for better mileage. I have not found any part or seal that changed part number when they switched to the HP. If I had a newer 4EAT, I'd dump conventional dex/merc in it.

Correction. All SOHC EJ25s list single layer. All DOHC EJ25s have MLS. At least in the US. There are several MLS gasket part numbers, they changed through the years. The most common problem number ends in 633, and can be replaced with number 642.

Oh yea, according to Uhaul, I only use their equipment to move 90s Corollas and Civics

The Diagnostic Flow chart for that (Subaru lists under P0638 to refer to P2101, so you might find more information that way) has 29 steps to it, and only the last 2 suggest replacing the throttle body. In short, it means that the ECU is asking for a target throttle angle, and the TPS reading it's getting back does not match. There are FSMs online in various places, I suggest looking it up and running through that chart for your car (FYI, the "U5" section is California Emissions) You are correct that the "sensor" is not a separate replaceable part, as it is integrated into the actuator and motor. It's actually 2 redundant sensors.

Yep, you have an electronic throttle. The throttle position sensor is built into the actuator. Replacing the sensor means replacing the throttle body. The sensor you're looking at is manifold pressure. Just because an ebay listing says it fits doesn't make it true.

Many 2004s are still cable as well (Legacy chassis, only Cali 2.5s and Baja turbos). But yea

www.partsouq.com Works with many manufacturers, and can lookup by VIN. I'm a dealership parts guy by trade, and I use it all the time. Sometimes has some good aftermarket interchange info, too. www.amayama.com has some, too. It's been a long time since I've used opposed forces.

So awesome. I love exploring that area! The time required to get my Outback or 4Runner into a condition to confidently do that is just not on my priority list right now. So I'm living vicariously through you!

I've had pretty poor luck with aftermarket ones leaking in less than a year. 25240KA041 genuine Subaru number, MSRP is $24.57. Every dealer has a pile of them (I have 15 at the moment). I used a Subaru switch on my Toyota Celica because I was tired of the aftermarket ones leaking and the Toyota one has an MSRP of $71

I've done a few different restoration techniques. None of them terribly difficult, and look great at first. But I generally see them start to cloud again within a year. I did one that involved protecting them with Spar Urethane, which I think lasted 2 or 3. Lately I just put some fine polishing compound on my buffer, and do a couple passes on them. I try to do this for our daily drivers every fall so they're perfect for the dark winter. The hardest part is finding the tote of car wash stuff and getting it out and an extension cord out to the cars. It's about 1 minute of actual buffing per car.

Yes. There is a calibration procedure for the Eyesight cameras. I think many glass companies can do it themselves (or maybe most of them just send it without calibrating....), but we do get them coming into the shop just for the calibration.