What transmission fluid / gear oil for rebuilt 6MT?

I've bought a "rebuilt by Porsche" transmission for my 50K-mile '02 Carrera and am going to be having it installed in the near future. What's the "best" fluid? I'm not going to use Porsche OEM because that's presumably what was in my existing problematic gearbox for most of its life, and I therefore don't trust it. (The factory transmission sometimes likes to pop out of first when engaging it at a stop, doesn't like to shift from second into third at more than 6000RPM, and has a slight howl that sounds like the pinion bearing is failing. A couple years ago, I tried several different transmission fluids and none of them made a worthwhile improvement. Buying this rebuilt transmission was several grand cheaper than having my existing transmission repaired.) This is the transmission that I bought: https://www.ebay.com/itm/222280734756

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I read every transmission oil thread on RL and elsewhere before I changed mine, and I came away with the opinion that the Porsche transmission oil seems to have the fewest "complaints" (e.g. things like balkiness when cold). Choosing the right transmission oil is much more about having the right formulation (e.g. lubrication, slip agents, etc.) to match with the internal transmission design/components than it is about "quality" of the oil. I believe that's why Porsche oil seemed to have the fewest complaints. I used the Porsche transmission oil, and was very happy with the results. I didn't have any shifting issues before or after the change, but it did shift slightly smoother after. I know you stated that you don't want to use the Porsche oil, but that would be my recommendation. It's a bit pricey, but transmission oil doesn't need to be changed very often.

I use Liqui moly as it has very similar specs to the porsche oem stuff. Fixed my troublesome shifting when cold.

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Specifically which LiquiMoly fluid?

Swepco 201. Amazon Amazon

I too went down transmission oil rabbit hole before and came to conclusion Porsche's was best overall option for general use. Most people bought others mainly because they were trying to save some money. I would be really surprised if their gear oil was the reason for your initial issues.... correlation does not imply causation. I will go get some popcorn now.

Another recommendation for Porsche transmission fluid. I changed mine maybe 10-20k miles ago, and the first gear engagement has improved greatly. I�m very happy with this fluid, compared to whatever was inside the transmission from the previous owner. i don�t know who makes the OE equivalent fluid, but I figured it�s worth the peace of mind to get it directly from the dealer. I�m not changing this frequently, like I do the engine oil.

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I couldn't get oem and i had no idea what was in it before. So did some research and went with the liqui moly 75w90 which had similar viscosities as the oem stuff. Shifting was improved from whatever was put in last time! If you have to ask, maybe just stick with oem.

there are different recommendations depending on if your car is equipped with an LSD or not I used Mobil 1 75/90 Synthetic which did not solve the cold shift issue that many experience with 996's but has been satisfactory so far there's some good reading in the 996 GT3 section which is where I wound up because my car is equipped with LSD https://www.zoro.com/mobil-1-gal-gea...35/i/G3460204/

That trans looks like a Genuine Porsche Reman....if so it is already full of oil.....but check it to be sure

Choice of oil had absolutely nothing to do with your failure. The sealed unit pinion bearings are a known weak point of the gearbox and has led to a lot of premature failures the last 25 years.

I use Swepco 201.

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i just got a 1999 with LSD -- what's the issue with using porsche oil with lsd? changing the gear oil will be one of the first things i do.

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https://rennlist.com/forums/search.p...rchid=49180620 settle in for some reading, it has something to do with modifiers and the additives that make the LSD work

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I had ChatGPT review all those and come up with a summary - does this align with your findings? ************ CHATGPT ************** Selecting the appropriate gear oil for a Porsche 996 equipped with a limited-slip differential (LSD) is crucial for optimal performance and longevity. Owners and enthusiasts have shared their experiences with various lubricants, highlighting the importance of choosing oils that meet specific requirements. Factory-Recommended Gear Oil: Porsche recommends Mobilube PTX 75W-90 for the 996's manual transmission and differential. This oil is formulated to provide excellent low-temperature fluidity and high-temperature stability, ensuring smooth shifting and effective wear protection. Users have reported significant improvements in shifting smoothness and a reduction in gear engagement issues after switching to Mobilube PTX. Alternative Gear Oils: Some owners have explored alternatives to the factory-recommended oil, especially when seeking enhanced performance or addressing specific issues: . Motul Gear 300 75W-90: This fully synthetic oil is praised for its high-temperature stability and excellent shear resistance. Users have noted smoother shifting and reduced gear noise after switching to Motul Gear 300. However, it's important to note that Motul Gear 300 is designed for gearboxes without LSDs. For transmissions with LSDs, Motul offers Gear 300 LS, which includes friction modifiers suitable for limited-slip differentials. Mobil 1 Synthetic 75W-90 LS: This oil is formulated with friction modifiers for limited-slip differentials. Some users have reported satisfactory performance, including quieter operation and smoother shifting. However, others have observed that it may not match the performance of the factory-recommended Mobilube PTX, particularly in terms of shifting smoothness. Considerations for Limited-Slip Differentials: When selecting gear oil for a 996 with an LSD, it's essential to choose a lubricant that includes friction modifiers to ensure proper differential operation. Oils lacking these modifiers may lead to chatter or reduced effectiveness of the LSD. Therefore, while alternatives like Motul Gear 300 offer benefits, it's crucial to use variants specifically designed for LSDs, such as Motul Gear 300 LS, to maintain optimal performance. Conclusion: While the factory-recommended Mobilube PTX 75W-90 is a reliable choice for the Porsche 996 with an LSD, some owners have found success with alternatives like Motul Gear 300 LS and Mobil 1 Synthetic 75W-90 LS. It's important to ensure that any alternative gear oil used is compatible with limited-slip differentials and meets the necessary specifications to maintain the vehicle's performance and protect its components.

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Gt gears knows what they're talking about. Chat ai GPT blah blah blah. Bottom line is Matt probably knows more about these than anyone and in the past he told me the Porsche gear oil just works better For our cars. Get it. Couple of shekels more but Worth it in this case. If that doesn't help it's time to whip out your plastic for some big money therapy. And, as always, go easy on the first 15 or 20 shifts. Done.

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ChatGPT was just fun way to summate the 100s of posts that Fracture linked to of Rennlist posters. GTGears didn't actually recommend a specific oil in his reply. Personally, I used Porsche's for my non-LSD gearbox and I said so from the very beginning of this thread. I'm only now just learning that there are major opinion differences for the LSD specifically.

Oops. I think that came across a Little strong. It was kind of a poke at the revolution of AI which already has significant impact. In any case I went through this including dumping brand new gear oil that previous owner had claimed install. I tend towards skepticism but I have to admit that it was remarkable in its improvement for my gearbox. Definitely recommend it and My own feeling is that other alternatives might match performance but likely would not. I had a similar experience with a 964 transmission in which case Matt's recommendation regarding friction modifiers made a similar significant improvement and that was not a Porsche additive. I would say his advice is a real benefit to us.

Thanks for the kind words all. I tend to stay out of the oil wars. My statement that the oil didn�t cause the failure is my endorsement of the factory fill.

Another vote for Swepco 201, but if it's full of Porsche oil, it's good for some number of miles.

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I understand about the pinion bearings--I did some reading on the issue. My concern is with the first gear (occasionally pops out when engaging first gear at a dead stop) and third gear (hard to shift from second to third at 6000+ rpm) issues, that I suspect might be related to the type of fluid used in the transmission. Or, maybe a previous owner (I bought the car with 38K miles on it) was hamfisted on the shifter and caused the issues.

So there have been several recommendations for Swepco 201 in this thread (and in other threads I've found) but I've also seen at least one person say to "avoid it at all costs", and I've seen others say that Swepco 201 is best suited for earlier Porsche manual transmissions (like 930-era). I'm a little hesitant to commit to a non-synthetic transmission fluid. I'd also really like to see some driving impressions from the Swepco 201 users. How's it shift cold? Hot? Any issues engaging gears at high RPM? Any popouts? I've emailed the seller of my Porsche-rebuilt transmission to see if the transmission has fluid it in (rather than pulling the fill plug and tilting it to the side slightly, since the transmission is still firmly in its shipping materials); if it does, I'll let that ride. If not, Motul 75W90 non-LS sounds like it might be a good choice.

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Whatever oil it has in it, I would very strongly recommend that you first drive it with that oil to evaluate the transmission you bought. If you change the oil before using the transmission, and find something like it not shifting well when cold, you won�t know if the transmission or your different oil is at fault. Test it with the same oil the rebuilder used to test it. It�s also a good chance to test whatever oil it has against whatever oil you decide to replace it with.

The place that rebuilt my transmission stated very clearly on the invoice not to use Swepco. He recommended Mobil Delvac which has LSD ingredients. But, my 996's transmission is a G50 not a G96 so my gearbox builder's recommendation is not really relevant. I am quite satisfied with the Delvac.

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This is good advice. I emailed the vendor and was told that, unfortunately, the gearbox shipped dry, so I'm going to order the Motul Gear 300 75W-90.

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I switched to Swepco 201 80W-90 from Porsche branded gear oil. Neither of them eliminated my transmission's tendency towards balky shifting when cold. Swepco produces better shifts once things warm up a bit. I had a notchy second gear engagement that I have pretty much forgotten about since switching to Swepco.

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So you are buying the LS or non-LS version? I assume the LS bc you say it has LSD ingredients, but I'm getting super turned around researching all the LSD/GT3/Delvac posts. It doesn't seem like the LS version is available in the U.S. so the Devlac sold here would not have LS additives, and it's just normal gear oil. From Euro version of Mobile's site, you can see they carry two products. The Non-LS one is what we have in the U.S.A.: (LS) https://www.mobil.com/en-pl/commerci...r-oil-ls-75w90 " Mobil Delvac™ 1 Gear Oil LS 75W-90 is a fully synthetic, limited-slip gear lubricant that been formulated from s....." (NON LS) https://www.mobil.com/en-hu/commerci...gear-oil-75w90 " Mobil Delvac 1 Gear Oil 75W-90 is a fully synthetic drivetrain lubricant engineered to meet very demanding extended drain and warra..." It seems the non-LS version is for 911's withOUT an LSD. So where did the "you need Delvac for the LSD" come from? I'm not saying it's wrong, but I also read (in Renn, so take at arms length), that you should NOT put any additives for LSD in the 996 LSD. Which means the non-LS version is what you should use, but then the whole "it's got LSD additives" is actually wrong.

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I don't have a Porsche LSD, I have a Guard GT2 LSD. You are correct I am buying the Delvac that's available in the US; I guess I didn't read I just bought. Both CMS and Guard suggested this Delvac. I can tell you that FOR SURE my limited slip is working. For the OE 996 LSD, likely by now it's worn out and needs to be rebuilt. Guard sells the plates that fit the OE limited slip, I believe. The limited slip additive is also available separately. I think there is a Ford LSD additive that can be had the the Ford dealer.

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that�s likely from the previous owner�s driving style. on Swepco 201 it is an excellent �racing� oil. I do NOT recommend it for street cars because it shifts very poorly when cold, and takes a long time to warm up on the street. It�s just not the right fit here.

The LS additives are to REDUCE the effectiveness of the LS unit. They are friction modifiers to prevent wheel chirp when turning corners. Typically it is added in small amounts until the LS unit is not to harsh for the driver. So for grandma - add a lot, for performance - add little. -Tom

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that�s interesting. Thanks for the education!

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^^^ this...I can vouch for the Ford limited slip additive... been using it for decades in limited slip differentials.. It is made from Whale Sperm...or is it from the Sperm Whale...something like that ...

Interesting about the Ford limited slip additive for Porsche. For Ferrari's, it was always GM's limited slip additive that was recommended.

Ok so the take away is, after all the posts saying Delvac is better because it contains LS specific additives, in reality in the USA it's just another trans oil and does not actually have any LS additives in it at all. Still think I'm going to go with Devlac for the LSD car though. And hold off on the additives. Probably need a new LSD anyway - but haven't even been able to drive the new car yet.

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Thanks for the clarification. Does it hurt to use gear oil with limited slip additives in a transaxle that doesn't have an LSD?

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I wouldn't think so. The additives are there to reduce friction between the steels and the clutch discs in the clutch pack, which lessens the grip the LSD unit can provide. And someone mentioned the GM LSD additive - those come in very small bottles, so I would expect the amount of additive in a quart of fluid that is shipped with the LS additive is a very small amount. -Tom

I would not use a gear oil with an LS additive in a non-lsd car. LSD additives are slippery, designed to reduce friction. Synchros require friction to work. When you make things more slippery, shifting can be more clunky and your synchros (the principle wear item in a gearbox) will wear out more quickly. There is generally a lot of confusion around LS additives, and I fear some of it is related to my comments related to my products being applied universally. with my LSDs, and our proprietary friction coating, it has been my experience that LS additives greatly reduce the lsd effectiveness, increase gearbox temperatures, and accelerate wear, in a racing/track environment. So I tell people not to use them, and thus why oils like Delvac and Swepco 201 are my top choices, and I again stimulate for racing, in that statement. The Porsche factory gear oil does have an additive package in it, that Porsche has developed in conjunction with Exxon Mobil to suit their gearboxes and their needs. I would not term it an LS gear oil, and would consider it compatible with any Porsche gearbox, LSD or not. And I consider it fine to use with my LSDs. when one branches out into other oil options, and other LSD options, one needs to ascertain their own specific needs and tradeoffs. An LSD additive will make the LSD in your street car more quiet and more smoothly operating. That�s its purpose. If you start experimenting with LS additives outside of a gear oil that is formulated with it, my one warning would be a little bit goes a long way. Like I would start with 1/3-1/2 the manufacturer recommended amount and only add more once you see how your own car drives afterwards.

Great reply! I got a 1999 with LSD that I want to prioritize for the track but still drive canyons. It sounds like I'll likely need the Guard LSD upgrade as the stock LSD is probably past its lifespan, but we'll see, I haven't even put it in third gear yet. Second is notchy, and crossing fingers it's just the gear oil has never been changed (very loose feeling stick). On my other 1999 (no LSD), I used Porsche gear oil and it 100% fixed the notching 2nd gear and stiffened up the shift feel when cold. For this new 1999 LSD will be going with Delvac. And since it comes in a gallon container I only need one, right? And just to confirm, this is it? https://www.summitracing.com/parts/m...-fluids-sealer

Correct. on your factory LSD, we do make a clutch kit for it. It can be rebuilt using our parts, for better longevity and performance. You don�t have to go through a whole new lsd install to make it work well enough.

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Thanks for all of the details. Sounds like the (non-LS) Motul Gear 300 75W90 should be a safe bet for my rebuilt transaxle.

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Oh i didn't realize you are Guard! I just went to the website and saw the contact email is your Rennlist handle. And yes, that's what I meant, rebuild kit. ( From prior searching for this, is this the kit? https://www.sharkwerks.com/transmiss...7-2-gt3-rs-4-0 ). How many hrs labor do you think I should anticipate so I can budget... Also, side note, on your website a lot of your images are not loading due to their being pointed to the server path, and not the web path. It's likely a minor update, but you just need to remove " /hermes/walnacweb04/walnacweb04am/b2539/moo.guardtransmissioncom/site " from the path in whatever page/plugin is loading those images. Removing that will show the images, example where I fixed it in browser:

Sorry, my website is trash. I need to find a professional to help me redo it in so many ways. yes, same kit that SW sells.

Following up on this thread, I finally got the rebuilt transmission installed about a month ago, and had it filled with Motul 75W90. This stuff. https://shopmotul.com/product/gear-3...SZBvmLsc-8L-HP I first drove my 911 in cooler weather. The howl from the pinion bearings was gone, as expected. I drove it hard, and near-redline shifts from second to third gear went in smoothly. However, engaging first gear at anything above a walking pace was difficult was a bit grouchy--I could downshift to first gear if I rev matched exactly, usually, but not always. Come to a complete stop, or almost stop, and the shifter snicks into first just fine. The old transmission did the same thing. Then a couple days ago, it was in the 80s and I drove the 911 around town a bunch--got the transmission good and hot. Lo and behold, the third gear issue resurfaced, just like with the original transmission--third gear wouldn't engage when shifting from second to third at 6000+ rpm.. And downshifting into first gear above 5-10 mph became basically impossible no matter how perfectly I rev matched. So, if my 50K mile factory transmission and a factory rebuilt transmission have the same characteristics, apparently G96-001 transmissions just suck. The Porsche factory oil didn't help when I used it in my original transmission, so I'm not going to bother trying it now. Swepco 201 80W90 seems like my next best choice. If it's notchy when cold and takes a long time to warm up, hopefully it's thick enough to make the synchros behave like they're supposed to when hot. I'm open to input or suggestions.

Swepco will be balky when cold* but I find that it smooths out pretty quickly. More now that it has some miles on it. * 'Cold' being any initial start after the car has sat overnight. Colder conditions mean longer warmup period. In my experience none have been excessively long, about the same amount of driving that brings the engine into the zone.

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Maybe a long shot... Have you increased the length of the cable? When I bought mine I had a similar 3rd gear problem. Under high load it would pop out when putting the clutch in. I increased the length of the cable and the problem moved to 2nd. Then I halved the distance that I moved it and it's been good for the last 20k miles. More recently we got our VW R back from a shop with a new clutch and it was shifting like crap, better when hot, but still quite notchy on 1-3-5. It was the same thing. Reset the cable length on the elevator cable and it's back to smooth. Good luck!

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interesting suggestion. I�m sure nothing has been changed with the cable lengths, and since the cables have been a constant, that could explain why two different transmissions have the same symptoms. I�ll look up how to set the cable length.

I discovered that Swepco offers an 80W140 GL5 fluid. If my 911�s transmission shifts fine while cool, but has the first and third gear issues when warm, could that mean that the fluid is getting to thin when hot? If so, would switching from a w90 to a w140 be a potential good solution? https://a.co/d/7P0wD7U

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Well not sure who actually rebuilt this tranny or what exact things they actually did in your tranny. eBay is not known for the best rebuilders of anything.... But can tell you without doubt the complaints you have noted above are not part of a proper operating transmission. If cables are adjusted correctly and tranny is installed correctly it should shift into any gear when appropriate. And the exact tranny fluid is not the cause of your problems, something mechanical is wrong if you can't appropriately select/shift into a gear whenever you so desire.... I'd double check the cable adjustments and if correct, talk to the 're-builder' (saying this loosely) and explain your problems and see if they will make it right. Just for the record, all the m96 transmissions I've owned worked good, any gear was selectable at any appropriate time. Shifts at redline are smooth and precise. jmnsho

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Nobody should take my advice, because I've only changed my transmission oil once. That said, because I didn't know anything about it, I searched all the RL threads on transmission oil extensively keeping track on comments on different oil types, and the factory oil seemed to have the least complaints by far. If you evaluated the factory oil of your old transmission when it was already having issues, that probably wasn't a fair evaluation. My transmission with 85k miles has never had an issue with cold shifting, or any other issue. I'm pretty sure it has only had the factory oil over it's lifetime, which is what I used when I changed it. I would suggest the factory oil is the best starting point for your rebuilt transmission, both to evaluate performance of the transmission and to have a case to go back to the rebuilder. It's not normal to have shift issues or cold shift issues (at least in my car). Particularly if the rebuilder used factory parts, I would take the oil brand/type variable out of the equation.

I looked into adjusting the shifter cables. I first read up on adjusting the cables at the shifter itself, but I read in this thread https://www.6speedonline.com/forums/...-smooth-2.html that the only thing that adjusting the cables at the shifter does is adjust where the shifter sits when it's in neutral (and, by extension, the gears, when they are engaged). Since the shifter seems to be properly centered, I don't think there is any point in miessing with the adjustment. So I got under the car and checked the cables where they connect to the transmission. On the transmission arm that is affected by the fore and aft motion of the shifter, when I would put the transmission into any of the gears, there was play in either direction. IE, when I would put the trans into third gear while underneath it, when third gear was fully engaged, the cable had a bit of play and could move a tiny bit farther before stopping. This seems to me to indicate that the shifter or cable adjustment is not impeding the engagement of any of the gears. If I was engaging third gear and the cable wouldn't move any further when it felt like third gear was engaged, then maybe the shifter or the cable was preventing full engagement. To clarify, this transmission was sold to me by a shop in southern California (don't remember which one, it's in my email somewhere) as rebuilt-by-Porsche. I would hope, perhaps falsely, that Porsche would do a "good job" on a rebuild. I was told that this shop had bought a bunch of these transmissions years ago and this was the last one left. Also, this was close to a year ago, so I am positive that there is no warranty.

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A couple of things to think about from a guy that has been tooling around on the street and track in his 996.2 for 22+ years. 1. Do not ever try to go into first gear from second driving at 5-10 miles an hour in the 996. It won't be pretty. 2. Do not jam the 996 shifter into any gear at any speed. It doesnt like it and will never like it. Instead, shifting in the 996 is a guided smooth rhythm between the clutch, shifter and right foot. You can do it really fast, once you stop trying to force it and just guide it instead. 3. Make sure the clutch pedal is on the floor before you shift. Rhythm, rhythm, rhythm.

@thefleshrocket I see you are in Carbondale, i am in Wheaton. Feel free to pm if you ever want to connect. You are welcome to drive my 996 to compare and contrast.

Quotes source post: 20083744

First of all, there is only one place to adjust factory stock shifter cables in a 996 and that is at the lever. Adjust them so that each cable can move as far as necessary to fully engage the gear; verify this at the gearbox. Yes it does mean a lot of up-and-down crawling around. Porsche sells a tool but in my experience it is of limited usefulness. A good starting point though. Secondly I am unaware of a Porsche branded rebuilt gearbox. I'm happy to be corrected however.

Yeah. Assuming the trans is in good working order, it could be the cables in the shifter need to be aligned, or cables under the car, or the trans and engine mounts are toast. It could also be shifting style. If you drove a Honda and now are driving a 996, you cant shift the 996 like a Honda. A buddy of mine is a muscle car guy amd used to jamming the shifter into only 4 gears. He had a hell of a time learning finesse while driving the car. Long throw clutch, long throw shift, therefore a longer rhythm. Lastly, it could be a bad rebuild and it needs to be rebuilt again.

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1. This sounds like your experience mirrors mine, which leads me to think that it's normal for the G96.01 transmission to be grouchy about downshifting to first while moving. Is there any speed at which the transmission will happily downshift to first, aside from being at a (near) stop? 2. This describes my technique. No forcing, just "guiding". 3. I am confident that the clutch pedal is on the floor when pulling the transmission out of its previous gear and while attempting to insert it into the next gear.

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Appreciate the offer. I went to College of Dupage so I am somewhat familiar with the area. I'm in the Indian Head Park area several times a year to visit family, so I'll reach out to you the next time I'm in town. Will probably be early Fall as I was just up a few weeks ago.

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I found this video that shows how to check cable adjustment at the transmission. It's the Numeric adjustable cables, and my car has the factory cables, but I think the principle for testing the cable adjustment is sound. Unfortunately, I did not request any paperwork or confirmation for the supposedly-rebuilt-by-Porsche transmission. The case was all pretty and shiny, so whoever went over it at least refurbished that much. I didn't peek inside. You Tube

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The shifter seems to be exactly centered, given my visual inspection. I installed an aftermarket short shifter several years ago as part of the transmission troubleshooting process; it did not make a noticeable difference. The transmission mount seemed to be in good condition; I installed inserts years ago as part of the troubleshooting process, and they did not make a difference. I replaced the engine mounts with Torque Solutions semi-solid mounts, also years ago, and they didn't make a difference either. I later installed a Top Gear catted x-pipe, and with the Torque Solutions mounts installed, there was not enough clearance between the cats and the bumper cover, so I switched back to the OEM mounts (which appeared to be in good shape) and which provided about a finger's width of clearance. Changing back to the OEM mounts also did not have a noticeable effect. I've got 35+ years of experience driving numerous manual transmission cars of all different types, so I am confident it is not an issue with my driving style. I also drove a 2004 911 Turbo X50 a month ago, and its G96.50 transmission felt buttery smooth compared to the G96.01. (Unfortunately, the G96.50 is not a bolt-in replacement for the G96.01--I checked.)

Sounds like you may just have a very finicky trans. Regarding first, I dont put the car into 1st until its at a stop. As I approach a traffic light or stop sign, I usually heal toe shift as i downshift out of habit and as i slow in 2nd, i end up shifting to neutral as i stop. I dont go into first until I am ready to move.

The factory centering tool is only about $25, so it’s well worth using it in my opinion (I just did that when installing the Function First Shift Right kit). I’ve not seen any of the shifting limitations in my 996. I don’t really shift fast -- I don't shift it slow either, I shift it just like any other car. However, my son (who is very skilled on track), does shift it fast in autocross and has no issues with shifting. There is third to 2nd reluctance under max braking on track, but that is transmission mount/shifter play under max braking stress (neither of us can duplicate it on the street, presumably fixed now with the shift right kit). I think people try different oils to either to address issues they are having (shouldn't exist for new/rebuilt transmission) -- or to get something they think is “better quality than OEM", but it may not be. Getting the best transmission oil is much more about compatibility of the oil’s additives with the transmission’s design, than it is about quality of the oil. The dumbest guy in the room's (me, having only changed transmission oil once) recommendation remains to try the factory Porsche oil. It's a bit more more expensive than other brands, but seems like the safest bet to isolate oil vs transmission issue. .

Cheese and rice. Just install factory tranny fluid and eliminate that variable, then go from there. GT gears doesn't buy from Porsche, Porsche buys from GT. AI process that for a minute. And to be honest after that it appears there are other issues.

I'd spring for a set of cables and a slave cylinder before I started tearing the trans apart again. BTW the Turbo G50 gearbox is about a $12k unit if you can find one.

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I installed the OEM Porsche fluid in my original gearbox, which exhibited the same issues as this one (albeit to a lesser degree), and it did not make a noticeable improvement. I don't think it's worth the $100+ experiment to try something that I am just about positive won't help. So, let's pretend that I already tried the Porsche fluid and it didn't help. What is your next recommendation?

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If the slave cylinder was failing and not fully disengaging the clutch, wouldn't the shifting issues affect more than just third gear? Ditto with the cables?