996 Transmission Gear Oil - Does Brand Matter

2001 C4 Cab with 40k, I changed the transmission gear oil and used Royal Purple. I think the shift quality went down, particularly when cold. I have read that the factory mobile oil spec is best but looking for real world experience.

As long as it meets the required specs from Porsche. I am personally using Amsoil. https://www.amsoil.com/p/severe-gear...?code=SVGPK-EA

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mine is running with Mobil one. No issues at all. Yes some gear oils are better than others. The specs are a minimum level of quality. Based on my real experience 9,000 miles I would suggest you get factory. Mobil is also 100 group 4 and 5 synthetic not severely hydro cracked group 3 base oil.

I used LiquiMoly 75W90. No issues for me. Edit/Correction: ordered from ECS Tuning, ES# 258729

I use Driven 75W90, no issues either.

Yeah I've heard deviating from factory stuff is problematic. I just went with the factory gear oil from either Pelican or Suncoast (Cant remember which one I got it from) No complaints, transmission shifts fine cold or warm. At $40/liter its expensive stuff, but it beats having to do it twice if you're not satisfied with the result from using aftermarket oils.

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This is also my understanding. With regards to expense, this oil was still less expensive than the gear oil for my manual transmission Jeep.

I have zero dog in this fight, all I know is my local indy here in western CT (Speed Sport Tuning), which is renowned as one of the top Porsche shops (race & street) in the country, just did my car and they used factory spec Mobil1. They used LiquiMoly for the engine oil. FWIW

I did factory Porsche brand oil a few years ago when shifting at cold was tough, mostly 1st gear. It�s better now, shifts great, and no issues, even on the track.

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Me too. I shifts better now than it did with whatever was in it before - I assume factory spec, but I�m not sure�

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I've got liquimoly 75W90 Fully Synthetic Hypoid, sounds impressive, I'm about to change mine. Don't know what is in there now, or when it was last changed. Something to note, some folk seem to say fill it until it drips out the filter hole. But the recipe calls for 2.7 litres and I've heard you should not overfill, it might cause notchy shifts. 2.7 won't fill it to the brim. I'm going with the measured amount. It's like cooking. Science for your belly. Do the same for your car.

Fwiw, my indy uses UK based Miller's CRX75W90 Gear for both track and street cars. Never had a problem on the street or track. Everything smooth.

I used Porsche Pentosin for a drain and fill shortly after getting the car. A bit pricy but I have no complaints.

Manual transmissions, syncros, and limited slip (if relevant) performance are generally sensitive to the brand and type of oil used, but from the posts here, it looks like the 996 is pretty compatible with a number of quality oils. I will definitely use factory oil when I do mine because I feel it's important to get the best possible match for transmissions (of course, it's a presumption on my part that the OEM oil is the "best", but it should at least be the "safest choice", long term, absent more specific info about alternatives). A few questions : 1 . Is the factory drain plug magnetic and is it worth getting one if not? (I watched two videos, one said the factory plug was the magnetic and another replaced to original with a black magnetic plug) 2 . What are the torque specs for the plugs? (it looks like there are no crush washers) 3 . What is the capacity and do you fill it to rated capacity or till overflow? (a prior post said capacity was 2.7, and the longer video below says 1.2 liters -- 2.7 seems a lot more likely) Short video that replaces with aftermarket magnetic plug: You Tube Longer video that says "it takes about 1.2 liters": You Tube

Everyone has their favorite flavor , but if they are all laid out in front of me, I would pick Swepco 201, but I will always want clean/new over old/dirty, no mater the brand.

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Skip, how often would you change the oil?

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That's interesting. I used Swepco in all my air cooled Porsches and I use it in a 50/50 mix with Redline in the M5 but I didn't know it was a thing for *modern* cars. As far as the 996, based on my Amazon order history, I'm using either Motul or Redline. I don't remember which.

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I shoot for every 40K on the gear oil, but I don't sweat if I miss it a little. The Factory recommends every 120K, but I think they always overestimate that stuff to give a lower "cost of ownership" report. We have seen a lot of pinion bearings go out in the g96 transmissions at around 80K.. We bought the Swepco 201 in 10 gallon drums with a pump and wheels at the Porsche Dealership, until we changed Service Managers, he said it was too expensive...

Here's an old RL thread that has addition info on transmission oil => https://rennlist.com/forums/996-foru...nsmission.html

Interesting. The guy who just finished a 5-figures rebuild of my G50 transmission said absolutely do not use Swepco and recommended Motul 300LS. Since he's built hundreds if not thousands of these gearboxes I will follow his recommendation.

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Think I've seen this more and more since using Driven products.

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Yea, like I said, everyone has their favorite flavor. I usually stay out of these. If you really want to see heavy debates on oils, you should be involved in dirt bike groups and get started on two-stroke oils. Lots of pictures of sized pistons as proof of condemning some oils, and testimony of never had failure as proof of favorite flavor. I built my first two-stroke in 1969 at 13yo..

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LOL! Yup. What they rarely mention about the seized piston is the dozen other factors (air temps, mix ratios, jetting, warm up, etc, etc). Still nothing better than the smell and sound of a finely tuned 2 stroke running castor oil.

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I definitely miss the smell of Castrol R, almost as much as riding!

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Yeah I stuck more than my share of two stroke dirt bikes and racing karts. Never blamed the oil. Usually my fault for running them too lean. Lean is mean...but deadly!

Absolutely ,nothing smells better than a two-stoke burning castor bean oil...I miss my old CR500AF. If some would make a cologne that smelled like that , I would buy it.. https://www.facebook.com/tractioneragmagazine/videos/526854342099573 https://www.facebook.com/watch/?v=526854342099573

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My 996 TT's Getrag gearbox was ruined by the previous owner using aftermarket gear oil and taking it out of the "dealer only serviced" records (famous athlete who became dishonest and started cutting corners after he blew all his endorsement money). I had to send it to Stan at GBox, fixed it good as new....but it was not cheap. Never use anything but the OE fluids in these gearboxes.

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I always wanted and AF!

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Baseball player?

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i use to formulate test these products. The issue with small companies is that a bunch of them don�t get the proper testing approvals done by a third party. I don�t know anything about the driven gear oil but if it�s like their motor oil which doesn�t have any formal approvals on it. I would not putt it in one of my p cars even if it was given free to me. Mobil and porsche work a lot in testing and developing, since I saw worked with Valvoline Cummins i can definitely say that Mobil would know have information about a lot of stuff that other oil companies even the small independents will never see. You are free to put whatever you want on your car. Once again a retired CLS certified lubrication engineer , I use Mobil 1.

I dont recall what i used in mine, likely mobile 1 or the oem but it madw a noticeable improvement when i did it. Luckily not a hard job and not terribly expensive. Id redo it if i thought it was worse.

I went with Mobil 1 Delvac 4k miles ago when I did my clutch at 55k miles. It was noticably more sluggish in the beginning especially when cold as if it was a higher weight oil, but it only took a few minutes to get enough heat to feel right. Happy with it now and happy to not pay for the high priced choices. To the OP, I'd say give the Royal Purple a chance, after you've got a few hundred miles on it and fully warmed up hopefully it will be fine.

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Well there you have it. Never use anything but OEM oils....lol...Last time I filled my g96 transmission on my 99 6 speed Cab, I used Land Rover 75w-90 gear oil.. I guess that counts?? lol I replaced the 2nd gear synco's and did a mod to the shift arrestor to allow for more second gear engagement at 70K. I had some Land Rover 75W-90 left over from a previous repair of a Land Rover front differential. I knew I would probably never be doing another Land Rover repair, so I used the expensive stuff in my M96 transmission. Yes, haven't had any problem with it, performs great. The problem I have with oil companies, small and large, is the lack of head -to-head comparisons. All the testing they do on their oils and IF they test competitors oils, the head-to-head comparisons are not available. The things that really matter to me is the "extreme pressure oil film strength" and the "max temperature" along with "aeration resistance"... Other things such as long use intervals, corrosion resistance, ect, are also important, but to a much lesser degree, especially to us since we change oil WAY more often than recommended by manufactures or oil companies. But these things are what's advertised by oil companies, and they have a pact not to reveal head-to head- tests. The only person I know of is an engineer by the handle of Rat540,( a drag racing gear-head engineer) who publishes his head-to-head tests. I would not consider him the "end-all-be-all authority" on OIls, but he is the only one I know doing it, and I appreciate that .. If you know of any other head-to-head test please share.IF you really want to "geek out" on oils, read through his long data. but don't consider it to be all there is.. I would love to see head-to-head comparisons of "aeration resistance" of the top oils that perform well in "extreme pressure oil film strength", but none exist. If anyone knows of any please share. There is always more to this story..........

Here was my bill (gearbox repair only and this bill is several years old so the current-day cost is likely at least $1-2K higher). Stan from GBox verified my suspicion and definitively concluded in writing that the damage was from use of after market fluid. He says never use anything but the OE fluid. No one in the USA knows these gearboxes better than Stan. I didn't buy the fluid from him so what motivation would he have to lie about that or push me toward buying it from Porsche? Buying the fluid from Porsche is more expensive but that isn't making Stan any richer. If anything what has made Stan money is people using aftermarket gear oil.... and then needing him to fix it because it's a lot cheaper than getting a new gearbox from Porsche, which is the only option they will offer you.

Seems to me that the more often you change your Trans fluid, the better off you may be regardless of what high end fluid you use. If porsche says 120k, 40k sounds good to me since you run less risk of the fluid (any high end provider) loosing it's qualities. You would think if you track your car you would change it fairly often due to the constant gear changes. BWDIK? I'm just a guy trying to prevent any chance of failure on his 996. Appreciate the discussion!

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I'm surprised that they don't advise to use the gear oil from the company that make it for Porsche ,( Porsche doesn't make the gear oil) to save the customers some dollars on the same product. But specialist often recommend OEM products, Porsche Specialist recommend Porsche products Honda Techs recommend Honda , BMW ect., even Ford Techs recommend Ford/Motorcraft products.It is usually a very safe blanket statement, that keeps them out of debates...lol..It doesn't make me any richer either...lol I'll bet G-box has never seen a failure on a g96 transmission due to Land Rover 75w-90 gear lube... Gear boxes have very high pressure points on the gears, especially low gear, and the "ring and pinion", but they don't have to deal with all the contaminants from ring blow-by, like motor oil does. " in writing"??? Care to mention the offending "aftermarket oil" that was used? Inquiring minds want to know. Does this mean litigation happened due to this trans failure?? What exactly failed, and I assume you were not the one who put the aftermarket oil in..

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Yep, fresh lube beats old lube every time without splitting hairs on "who makes the best",( when you don't have the actual head-to head data)...

When developing a gear box(and engine for that matter) a lot of testing is done. Testing is done with only a few selected oils, imagine the time it would take to run thru the test program for every oil on the market. Thus, the gear box is known, and tested, to work with oil X. I might work equally fine or better with oil Y, but it is not tested or known from the manufacturers side. As a consumer you can ‘test’ the oil or you can skip that part and just get the OEM stuff….and that’s why specialist recommends OEM stuff, it’s tested and works. I recently changed gearbox and front diff oil and I didn't buy directly from Porsche. After some internet googling it was quite clear that the original stuff was "Shell Spirax S5 ATE". My car had Motul Motylgear in it before(previous owner used that), which is not recommended for transaxles...It felt fine and there was almost no difference in gear shift feel with the new oil.

Anybody know when Porsche formally teamed up with ExxonMobil as their "official" fuel and oil/lubricant provider?

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Stan never said to buy it directly from Porsche. He only said to exclusively use OE fluid and was very clear about that. As far as what failed I posted the bill above. The 1/2 3/4 synchros and shift sleeves were trashed etc. Reminder this was on a 996 TT Getrag which takes Mobilube PTX as the OE fill (believe there is also a Shell product which is OE too). When you would put it in 1st gear about 1 out of 20 times it would make a terrible banging and miss the shift. I will point out that you can change the fluid and the gearbox can operate perfectly (some even say better) for a long period of time -- like on the order of years depending on how much you drive the car -- before the damage manifests itself as was the case in my situation. This is how the seller was able to fool someone like me who knows exactly what to look for on these cars without disclosing it; it didn't show up on my test drive and passed a PPI from an independent well known Porsche dealer. I give that kid credit, he snuck it by me. I also want to point out that if you drill down and actually look at the specs of the gear oil it uses completely obtuse specs. It almost seems like the manufacturer went to lengths to keep the aftermarket from replicating the formulation, but that is pure speculation on my part as maybe there are other factors of which I am not aware. The PTX also also uses a specialized friction modifier. In the end I am not trying to make people paranoid or tell people what to do. I am only recounting my own experience in a facts based way. People can take that information and do what they want with it. But I am sure stuff like this happens all the time -- someone dicks the gearbox and then instead of taking accountability wants to make that someone else's problem..... unfortunately a lot of people are just like this.

I think with transmission oil it really is less about the quality level of any given oil and much more about how good of a match the particular properties of that oil are for a given transmission design. This is seen most profoundly with Ferrari transmissions, where from 1950's through mid-1990's when the 355 F1 transmission came out, second gear is typically reluctant until the car/transmission oil warms up. There, picking the best oil had far less to do with quality then it did about how the individual oil flowed through the transmission. A lot of people used a mixed of oils, or an oil plug GM limited slip additive to get it to work best. Ferrari had to finally fix it with the F1 transmission on the 355, because you couldn't skip 2nd gear till it warmed up. Ferrari's transmissions are an extreme example, but I suspect for all transmissions, having the exact right match for flowing through that individual transmission is much more important than quality (all of the known brands people would typically put in a Porsche are good brands). That why I'm definitely going with Porsche transmission oil, not even going to guess what brand/type that is to buy it for less. Well worth it to minimize wear long term. I don't think whether it shifts well is the "acid test" for long term wear -- I don't think anyone can really know how well any of them perform for long-term wear, so that again is why I'm going with OEM.

FWIW : gear oils are much simpler than engine oils because they do not have to deal with contamination from combustion by-products due to the piston ring blow-by getting into the oil and moisture from 13% of combustion gases being H20 (water). The duty of gear oil is simply the film strength to protect sliding and pressure of metal on metal contact, and also on some gear boxes the "slipperyness" of the lubricant will effect the syncro function. Syncro's use "friction" to match gear speed so the user doesn't need to "rev match" when changing gears. IF the lubrication is "too slippery" the synco's will not work well, such is the complaint from some users of Swepco. IF the syncro's are worn or questionable, a very slippery lubricant will expose this, where as a non-slippery lubricant will hide the issue. On gear boxes with clutch packs (LSD) or LSD differentials, a lubricant that is "not slippery enough" will cause chatter of the LSD, and a "friction modifier" is needed. The friction modifier makes the lubricant more slippery to eliminate the chatter. Friction modifiers are made from the Sperm Whale, or synthesized. Some gear boxes actually use automatic transmission fluid for lubricant. The Ford type F ATF is a very high pressure/non slippery lubricant that is used is some manual gear boxes. It is also used in Automatics that are modified with a "shift kit" to give a much firmer shift, and bark the tires on automatic shift. It is usually recommended by aftermarket companies who sell shift kits and high performance trans rebuild kits. Motorcycles/dirt bikes do not have synco's in the gear boxes ( they have dog gears) but they do have "wet clutches" in them. In the Dirk Bikes many people swear by Rottela in the gear boxes, many swear by HondaLube, YammaLube, ect. I have used Ford type F ATF in two-stroke dirk bike gear boxes for decades with excellent results. It is a a low viscosity (high horsepower) but gives excellent gear protection, and works extremely well on the "wet clutches".where more slipper lubricants (synthetics) fail. So, to put it simply, gear boxes need a lubricant that has a strong film strength, most any gear lube of the proper viscosity will provide this. But depending on the type of syncro, (or lack of) and IF you have an LSD (clutches) in the gear box, you have to chose "how slippery" the lubricant needs to be.Synthetics are generally more slippery than dino oil .Dino oils generally helps the syncro's work ( more friction) but can make the LSD chatter. Adding friction modifier will stop the LSD chatter, but makes YOU wear the syncro's more (if you don't rev-match).. Disclaimer :: I rev match everytime even when I'm just cruising because I know what goes on in syncro's and lubricants. It's just second nature and doesn't have to include high revs on down shifts like when racing, you just wait for the proper/time RPM to execute the shift. So, if you DON"T have LSD, and you have good synco's ( and take care of them), you can run pretty much any gear lube of the correct viscosity. I am not saying you can chose gear lube "Willie Nillie", just trying to educate and misspell some myths, and uncover some of the Mystery behind it all.

Great lesson Skip. Thanks.

My car was at 100K miles when I got it. Never shifted well when cold, even on a hot August day. Service records showed transaxle oil change at 90K miles, but not what oil they used. I read some threads here and decided to go OE Porsche. Cold shift issues are gone.

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@Porschetech3 Skip, Is there an LSD fluid that you like? Swepco as well? I feel like my LSD transmission (100k miles) likes Motul 300LS.

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So which one? I think I will change mine using the liqui moly I've already purchased, and change again in a few thousand to one of these ? Is one better than the other? Is delvac better than mobilibe? Price for Porsche oem is high, but so apparently are gearbox rebuilds. As an aside I think I read somewhere that there is a powerful magnet surrounding the gearbox drain plug. I'm going to test that. Can anyone confirm? For example see this thread

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The only info that I could possibly add to that excellent summary is, a combined transmission/differential needs a gear lube with EP characteristics because of the ring & pinion where a conventional transmission might not need EP lube; and beware of the API GL-4 vs. GL-5 if you have an older car with brass syncros because the sulfur-based ingredients in some GL-5 lubes will eat the brass syncros!

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Prf, could you translate this into English for us uneducated folks?

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The safest thing is to check the part# by your VIN (I do this for all parts and fluids for my cars). Places like Sunset Porsche take your VIN when you checkout which they will cross check. Yes, you're paying a premium but I estimate a gearbox rebuild is around $8-10K in today's dollars -- shipping the gearbox alone with rates these days is likely going to be $1-2K depending on where you live. Most transmissions/gearboxes do have a magnet. I have an Audi Q5 grocery-getter that has a ZF 8HP transmission. I have literally seen people ruin this transmission and/or their diffs including a person a month or two ago that said he drove only 10 miles before he had ruined everything. To do a change it requires 3 different fluids: the ATF, a gear oil for the front/rear diffs, and a 3rd special very expensive gear oil for the transfer case (also referred to as center diff). I purchased the documentation for my car from Audi but I see tons of people posting the wrong procedure and wrong oils on forums. My point here being do your homework because if you don't know exactly what you're doing you can quickly end up with a very expensive bill.

Excerpt below from 996 shop manual, answering 2 of my question in a prior post: 1. Capacity is 2.7 liter, fill to bottom of drain hole (rather than measured 2.7 liters) 2. Torque for both drain plugs is 18 ft lb (30 Nm) Still trying to figure out if the factory drain plug is magnetic

From USA/Canada 996 parts manual: This is the oil on Suncoast: https://www.suncoastparts.com/product/99991754600.html

The drain plug is not magnetic but I think there is a magnet close to the drain hole which can be reached by finger.

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Bentley and pelican both state it is too the front of the car adjacent to the drain plug. It's recommended to drain the fluid then to use qtip or something more substantial to clean the plugs as well as the interior of the tranny around the drain plug, before refilling, w the specific lube and in the specified amount for your vehicle.

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The plug on my �99 was magnetic.

I have motul gear 300 in my c4s. Works well. Not noticeably different after 10k km - maybe a bit smoother? I don't think the brand matters much. I went motul bc my indy stocks it.

Another data point on this. I recently changed my trans oil - first change after 17 years and 38K miles. At the suggestion of the guys at FSI I went with Swepco 201. Shifting feels much more precise, if that makes sense. The transmission needs about 5 to 10 minutes to warm up for first gear to feel easy to get into on a downshift. Overall very happy with the change, but that may be due to old oil out and new oil in. The car is a 40th AE, so it does have a LSD. I am in California so haven't had to deal with any real cold weather.

Not to dredge up an old thread, but now that it's getting deep into the bleakest part of our notoriously difficult southern California winter, I am once again thinking about shift quality when cold. According to maintenance records by the PO, the car currently has Porsche-branded 75w90 in it, which it has been running for around two years and 10k miles. When the car is warmed up, it shifts beautifully. When it's cold (talking about 50f or below) it can be a real bear to get into first and second. There's never any grinding or weird noises, no gear pop-outs or anything, it just takes more effort than I think it should to get the car into first and then into second. Now, this is a 2003 Carrera 2 with 144k miles on it. Prior to this current fill of Porsche genuine oil, it had Motul Gear 300 75w90 for 8000 miles and Red Line 75w90 GL-5 No Slip in it for 15k miles before that. Having never driven another high-mileage 996, is my high-effort shifting normal in that 40-50 degree temp range and is it worth trying other oil to see if it makes a difference? I have three liters of Liqui Moly 75w90 on the shelf that would work just fine.

I can only give my personal experience. 2004 C4S Manual with 103k miles. I used Liqui Moly Manual Transmission Fluid 75W90 about two years ago, and it's run great. However, it also ran great before I did the fluid change; I wasn't trying to fix anything. Just my 2-cents, YMMV, etc....

I just changed my transmission oil with the factory Porsche oil. I think it had Porsche oil previously, but not positive. I didn't have shifting issues in cold weather either before or after the oil change (70k miles). It did shift slightly better after the oil change.

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You�ll have to channel you inner David Goggins to get through that kind of misery.

2002 targa, 115k miles, Porsche oil. Shifts better than whatever was in there before. 2nd gear requires patience until things warm up and is more noticeable the colder it is. As for environment, I own a snowblower.

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Just a quick heads up regarding the Motul 300 75w90 oil: Motul make two 300 75w/90 transmission oils, one is semi-synthetic, the other fully : https://www.opieoils.co.uk/p-899-mot...ntial-oil.aspx The fully synthetic version above seems to get almost universally poor reviews once used in 996 gearboxes ... However the semi-synthetic version : https://www.opieoils.co.uk/p-68953-m...ntial-oil.aspx Is specifically recommended by Motul for : "Gearboxes which are hard to shift and/or noisy gearboxes. All mechanical transmissions, synchronised or non-synchronised gearboxes, gearbox/differential, transfer gearboxes and hypoid differentials without limited slip systems, operating under shocks, heavy loads and low revolution speed or moderate loads and high revolution speed." The above is quoted verbatim from Motul's information/data sheet on the semi-synthetic variant here : https://azupim01.motul.com/media/mot...0_20220616.pdf No it's not clear, and yes, it is really annoying ... (I only found out by noticing the price differential on various websites selling the two variants) I then did a deep dive and found the above data sheet ... I'd bought the semi-synthetic (luckily). I'd say it gave an improvement of 15, maybe 20% in shift quality, 1st to 2nd and back down is still "sticky" when cold (but less so) but it takes much less time for the 'box to warm up with the Motul, and the those awkward 1st to 2nd shifts become easier, more quickly, as a result.

[QUOTE=khyatt;19201124�.When it's cold (talking about 50f or below) it can be a real bear to get into first and second...[/QUOTE] My car, when cold, won�t take 1st gear easily unless I�m stopped. Are you trying to grab 1st while moving? For second gear, you�re obviously moving though, so I�m thinking you might want to check your shift cable alignment as well. It might not be the fluid. Some folks - many folks - have replaced fluid and have had little behavior change with shifting.

Agree. Big difference between cold weather and warm. With over 22 years shifting in my 996 its been pretty much the same. When the weather is cold, shifting is not friendly. When everything warms up, it's friendly. From my experience, trans fluid changes and new motor mounts helped when everything was warm and i highly recomend. But when the car is started in cold weather its gotta warm up first. Doesn't take long.

I've used Amsoil before and it was noticeably stiffer when cold than the fully synthetic Motul fluid I use now.. Motul also felt better on the track over the Amsoil.

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So the semi-syn is the one with a friction modifier? Looking at the two links they both say 100% syn

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My apologies This is the correct link to the semi-synthetic 75w90 Motul 300 : https://www.opieoils.co.uk/p-897-mot...variantid=1129 Could I ask you to delete your post that quoted my incorrect link post, and I will in turn edit that with the correct link, so that others won�t have to read both our posts to find the correct link ...

My experience is that it isn't so much about the "quality" of oil (all the brands being talked about are high quality) but that the formulation of a given oil matches exactly what the transmission design needs. Take this suggestion with a grain of salt because I've only changed the transmission oil on a 996 once from (what I think was) Porsche OEM oil to Porsche OEM oil, and haven't had any cold shifting issues. Yes, the Porsche oil is pricey, but my guess it that it is more likely to be a better match even if it isn't technically "higher quality" oil.

It makes a huge difference to how it feels, 1st is crap with most, 2nd is a bit rubbery, I would only used the PTX oil now, the difference between that and others is night and day. Not knocking the Motul semi btw. Atgani pointed the differences on the UK forum, so will try that next time.

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I changed mine at 38k miles when I bought it because I like to start with new fluids when I buy a new (to me) car. I'm pretty certain it was the original oil it left the factory with. I used Redline and noticed no difference in shifting with new vs old oil but I don't think I've ever driven it when its been below 70 degrees outside.

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So, after much consideration, I think I'm going to change the gearbox oil for the Liqui-Moly I have in the garage but I'll add in the LM MOS2 gear oil additive (not the engine oil version, calm down) to see what happens. Moly makes a ton of sense for use in a gear oil application and given that I daily my car, I should know pretty quickly whether its a change for the good or not. If not, I can always swap out for the Porsche stuff. As to the person who recommended shift cable alignment, I appreciate it, but the cables are new and I have zero issues shifting when warm. The cables are new stock Porsche genuine units (done like 6k ago by the PO) so we're all good there.

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In my experience, just because the transmission shifts well when it's hot, doesn't mean that it's action when cold can't be improved with some further adjustment of the cables ... Mark the cables accurately where they are currently, and then experiment, you have nothing to lose and everything to gain (as I found out)

Hi, Has anyone tried Redline gear oil in their manual 996?

Hey all, reviving this thread with a question: My 996.1 (6-speed, 150k miles) has a howling trans... yay. Pretty sure the pinion bearing is on its last legs. PO tracked it but never serviced the gearbox outside of the 30k intervals (FAIL) (but thankfully babied the engine with frequent oil changes). Regardless, it now it howls like crazy under load above ~55 mph, whether accelerating or engine braking. Drive me mad lol I'm currently sourcing a replacement G96 trans, but in the meantime I'd like to quiet it down as much as possible with a fluid change. (Let me know if you have one. I am located in Tulsa OK G96.00 for '99-'01 cars (mine is a 01))/ Should I go with stock Porsche fill (Mobilube PTX), or is there a thicker or “slicker” band-aid fluid that could help suppress the noise for now? Shortlist of fluids mentioned in this thread via AI: Porsche OE (Mobilube PTX, factory fill) Mobil 1 Delvac Liqui Moly 75W90 (I am biased to Liqui moly) Redline 75W90 (some bad cold-shift feedback) Motul Gear 300 (confusion: fully synthetic vs semi) Swepco 201 (hotly debated; some love it, others blame it for wear) Amsoil Severe Gear Oil Driven 75W90 Miller’s CRX 75W90 NT Porsche Pentosin Shell Spirax S5 ATE (OE fill for some market ⚠️ Additive: Liqui Moly MoS2 gear additive (optional) Goal: I do not really care what oil as this trans will be shelved soon, so I want whatever helps mask gear whine without risking synchros. This isn’t permanent - just want to limp quietly until I swap boxes. If possible, I think a heavier weight could possibly help. The howl gets louder the warmer the engine and or ambient temperature is. Let me know what you’ve had luck with on noisy gearboxes - especially for quieting howls. Thanks!

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Not that I'm a fan of additives, but I've spoken to several people who have used the Tribotex that have had notchy gearboxes and along with Swepco 201, that was the ultimate fix.

Quotes source post: 20050884

I don�t know if there is an official transmission oil change interval, but every 30k is more frequent than most 996�s see. Tracking shortens the interval, but 30k doesn�t seem particularly bad. It would probably help to know what oil the prior owner used.

I believe the original service maintenence schedule was every 90k miles to replace transmission oil. I've done mine on average at ~15k miles. I dont have any trans issues even with tracking the car for years, so i suspect its helped. No different concept than constant oil changes for the engine. But i did have to have my Guard LSD rebuilt after 10 years. But thats a known wear item while putting down the power on the track. Nevertheless, I have been pleasantly surprised at the durability of the 6MT on my 996.2.

I would replace the trans/diff oil somewhere between 5-9 years for a street car depending on mileage and use.