Best transmission/differential oil

[downtoearth]

If your having issues with the synchros, I'm guessing you had issues before the Amsoil.

 

I also see you have a 2.5i do they have the requirements as the 5 and 6mt in the GT's ?

 

HAMMERDOWN has been using this stuff in his mt for a long time. Both my cars have over 40,000 combinded miles on the stuff. Both will get it replaced before next winter with more of the same.

 

The redline and Motul may help the synchros if you catch it before they are to bad.

 

 

it it my understanding they that 5mt is the same on both the 2.5I and 2.5 GT except the push/pull clutch

 

but

 

I had no issue before putting the amsoil in. I had Mobil 1 in it before that. I had the Amsoil put in before my cross country drive (arizona to ct) back home during my 60k service. It worked fine for a while and then i started to notice a quick grab/clip when down shifting to pass, and the grab got harder and harder and turned into a full out doogteeth grind. It was to the point where I had to rev match to downshift 5 to 4th to prevent damage.

 

i took a quart of the amsoil out and put a a quart of syncrhomesh in and it all stopped within 10 miles of driving. its been 100% ever since.

[Max Capacity]

Can you confirm/ refute the statement that the redline combo will eat the synchros?

 

For that you'll need to contact BAC5.2

 

it it my understanding they that 5mt is the same on both the 2.5I and 2.5 GT except the push/pull clutch

 

but

 

I had no issue before putting the amsoil in. I had Mobil 1 in it before that. I had the Amsoil put in before my cross country drive (arizona to ct) back home during my 60k service. It worked fine for a while and then i started to notice a quick grab/clip when down shifting to pass, and the grab got harder and harder and turned into a full out doogteeth grind. It was to the point where I had to rev match to downshift 5 to 4th to prevent damage.

 

i took a quart of the amsoil out and put a a quart of syncrhomesh in and it all stopped within 10 miles of driving. its been 100% ever since.

 

 

When I had my tranny buddy rebuild my 5mt he needed to get both the pieces that some think are the differences between the 2.5i and the GT tranny.

 

So may be they are the same. I don't know much about the rebuilding process of the tranny. My guy worked for a long time at a local tranny shop and rebuilt and raced bikes for a while. He built our honda tranny's for the race car.

 

 

"amsoil out and put a a quart of syncrhomesh"

 

I'd like to know what BAC5.2 thinks about that. He's also kind of a tranny expert.

[mack4657]

i am a newbie here just picked up an 05 legacy with 108,000.... i am planning i chaning my trans fluid on my m/t asap... so redline is best trans fluid to run??? and changing is the fluid is just a drain and fill..... and the drain plug is hex right? thanks for the help!

[supraru]

For that you'll need to contact BAC5.2

 

 

 

 

When I had my tranny buddy rebuild my 5mt he needed to get both the pieces that some think are the differences between the 2.5i and the GT tranny.

 

So may be they are the same. I don't know much about the rebuilding process of the tranny. My guy worked for a long time at a local tranny shop and rebuilt and raced bikes for a while. He built our honda tranny's for the race car.

 

 

"amsoil out and put a a quart of syncrhomesh"

 

I'd like to know what BAC5.2 thinks about that. He's also kind of a tranny expert.

 

It really depends because there has been plenty of updates over the years. The only thing I'm completley sure of is the 05 lgt gears are the same that are in the new wrx's down to the ratio's and part numbers. Only thing that is different is the ring and pinion gear wise. I'm also fairly certain that in that same year there was no difference between the gt's and non turbo's as far as actual gears go. I really don't see why there would be a difference between a turbo version and a non turbo version of that same year besides the final drive. Now from year to year that's a whole different game. There are always small improvements they try to make.

 

i am a newbie here just picked up an 05 legacy with 108,000.... i am planning i chaning my trans fluid on my m/t asap... so redline is best trans fluid to run??? and changing is the fluid is just a drain and fill..... and the drain plug is hex right? thanks for the help!

 

You don't need redline shockproof. Just buy the regular 75-90 fluid and you'll be fine. My number one has been Motul gear 300. Has performed best. As I have stated I have gone through tons of different set ups on my subaru 5 speeds since 2001. Most guys have crappy fluid in their trans then go to this magical cocktail and think it's the best thing ever made. Zero need for it unless it has issues.

[Max Capacity]

i am a newbie here just picked up an 05 legacy with 108,000.... i am planning i chaning my trans fluid on my m/t asap... so redline is best trans fluid to run??? and changing is the fluid is just a drain and fill..... and the drain plug is hex right? thanks for the help!

 

I think it's a 70 torx, you need to raise the back of the car to get all the fluid out.

 

Redline with the Motul if you have issues.

 

Extra-S or the Amsoil Severgear 75w-90 seem to work fine.

[BAC5.2]

Dylan from ds1 is very knowledgeable.

 

There's your first problem. You are taking advice from someone who tried to suggest that Kartboy short shifters caused transmission shift selector seals to leak. Someone who turned blue in the face to suggest that the Cusco transmission mount was 5MT or 6MT specific. I've actually taken apart transmissions he assembled, and I wouldn't trust him to fix a sandwich. And that's ignoring his utterly shady business practices and the fact that "DS1" is no longer a company after he screwed more than a few people out of more than a little bit of money.

 

As for Shockproof "eating synchros", that's a load of bollocks. I ran straight lightweight shockproof in my Forester for 100k, without any issues whatsoever. I've run it, and suggested it, for hundreds of Subarus without a single negative report. I've even torn down transmissions that have been running the Motul/Shockproof combo for a LONG time without any problems.

 

You should NOT use Synchromesh in a Subaru 5MT. Synchromesh is a fluid intended for gearboxes requiring GL-4 fluids. GL-4 fluids can't handle the shear loads seen in high offset hypoid gearsets (like our front differentials), and you'll see over time that fluid shears and wears the ring and pinion down to nothing in cars driven hard. I have a scar on my right index finger where a ring gear sliced through my glove.

 

Any GL4 fluid will cause this, not just Synchromesh. MT90, for example, will do the same thing. There was a small company who built kit race cars using the Subaru 5MT converted to FWD. They were running MT90, and were destroying front diffs after just a lap or two. They switched out to Motul/Shockproof and never had the issue again.

 

I've said for years, my preferred trans fluid setup is Motul and Lightweight Shockproof. It's what I recommend. As an alternative, I suggest Extra-S, Motul, or any other high quality synthetic. I don't recommend Royal Purple, Mobil 1, or Redline's 75W90NS, based on poor results. I am also a huge supporter of frequent fluid changes. I typically change my trans and rear diff fluid every 15-20k miles.

[Nolmers06LGT]

There's your first problem. You are taking advice from someone who tried to suggest that Kartboy short shifters caused transmission shift selector seals to leak. Someone who turned blue in the face to suggest that the Cusco transmission mount was 5MT or 6MT specific. I've actually taken apart transmissions he assembled, and I wouldn't trust him to fix a sandwich. And that's ignoring his utterly shady business practices and the fact that "DS1" is no longer a company after he screwed more than a few people out of more than a little bit of money.

 

As for Shockproof "eating synchros", that's a load of bollocks. I ran straight lightweight shockproof in my Forester for 100k, without any issues whatsoever. I've run it, and suggested it, for hundreds of Subarus without a single negative report. I've even torn down transmissions that have been running the Motul/Shockproof combo for a LONG time without any problems.

 

You should NOT use Synchromesh in a Subaru 5MT. Synchromesh is a fluid intended for gearboxes requiring GL-4 fluids. GL-4 fluids can't handle the shear loads seen in high offset hypoid gearsets (like our front differentials), and you'll see over time that fluid shears and wears the ring and pinion down to nothing in cars driven hard. I have a scar on my right index finger where a ring gear sliced through my glove.

 

Any GL4 fluid will cause this, not just Synchromesh. MT90, for example, will do the same thing. There was a small company who built kit race cars using the Subaru 5MT converted to FWD. They were running MT90, and were destroying front diffs after just a lap or two. They switched out to Motul/Shockproof and never had the issue again.

 

I've said for years, my preferred trans fluid setup is Motul and Lightweight Shockproof. It's what I recommend. As an alternative, I suggest Extra-S, Motul, or any other high quality synthetic. I don't recommend Royal Purple, Mobil 1, or Redline's 75W90NS, based on poor results. I am also a huge supporter of frequent fluid changes. I typically change my trans and rear diff fluid every 15-20k miles.

 

Thanks for the info. What is your opinion of using MT90 for the rear diff?

[BAC5.2]

Thanks for the info. What is your opinion of using MT90 for the rear diff?

 

You should be using a GL-5 in the rear diff, also. So no MT90 there, either.

 

I only use Motul300 in the rear diff.

[Nolmers06LGT]

You should be using a GL-5 in the rear diff, also. So no MT90 there, either.

 

I only use Motul300 in the rear diff.

 

Ahh.. ok. I have Motul300 that I intended to throw in the rear, but a friend of mine was trying to trade MT90 for the Gear300. Looks like I'll have to tell him the trade is a no-go. Thanks!

[downtoearth]

There's your first problem. You are taking advice from someone who tried to suggest that Kartboy short shifters caused transmission shift selector seals to leak. Someone who turned blue in the face to suggest that the Cusco transmission mount was 5MT or 6MT specific. I've actually taken apart transmissions he assembled, and I wouldn't trust him to fix a sandwich. And that's ignoring his utterly shady business practices and the fact that "DS1" is no longer a company after he screwed more than a few people out of more than a little bit of money.

 

As for Shockproof "eating synchros", that's a load of bollocks. I ran straight lightweight shockproof in my Forester for 100k, without any issues whatsoever. I've run it, and suggested it, for hundreds of Subarus without a single negative report. I've even torn down transmissions that have been running the Motul/Shockproof combo for a LONG time without any problems.

 

You should NOT use Synchromesh in a Subaru 5MT. Synchromesh is a fluid intended for gearboxes requiring GL-4 fluids. GL-4 fluids can't handle the shear loads seen in high offset hypoid gearsets (like our front differentials), and you'll see over time that fluid shears and wears the ring and pinion down to nothing in cars driven hard. I have a scar on my right index finger where a ring gear sliced through my glove.

 

Any GL4 fluid will cause this, not just Synchromesh. MT90, for example, will do the same thing. There was a small company who built kit race cars using the Subaru 5MT converted to FWD. They were running MT90, and were destroying front diffs after just a lap or two. They switched out to Motul/Shockproof and never had the issue again.

 

I've said for years, my preferred trans fluid setup is Motul and Lightweight Shockproof. It's what I recommend. As an alternative, I suggest Extra-S, Motul, or any other high quality synthetic. I don't recommend Royal Purple, Mobil 1, or Redline's 75W90NS, based on poor results. I am also a huge supporter of frequent fluid changes. I typically change my trans and rear diff fluid every 15-20k miles.

 

 

i'm curious, how would adding a quart of synchromesh fix my problelsm with my synchros (before creating a bigger one as you jsut told me), does it make the amsoil synchromesh combination more slick? or less slick and allow the sychros to have friction? Does it have to do with the wax in the synchromesh?

[bugblatterbeast]

you just thinned out the mix. that makes it easier to squeeze the oil out from between the synchro rings and the cone on the side of the gears. the grooves on the inside of your synchro rings are probably dull. thinning the oil just makes it easier for them to function despite being worn.

[Impatient]

2 part question:

 

is the lower mark actually 1 qt low, or some other amount?

 

Assuming Mobil Delvac 75w90 synthetic is what's in there now, is there any know problem adding Motul 300? The Delvac is a bit thicker at lower temps than Redline and certainly thicker than the Motul.

[ama0787]

sorry but I find cocktails to be a joke I believe bitog had some negative info posted specifically about scottys cocktail but everyone has there own opinion and if it works for you keep doing it,,,, I have 2 cars and have changed fluid in both the transmission and have never noticed a difference before or after maybe it is bc i keep all in good working order so any oil will do but I just always run high quality synthetic oil in engines trannys and rear ends and have no problems switch them up occasionally never notice a difference ...

 

I think changing fluids correctly and at proper intervals is key

 

*edit*I noticed mention of synchromesh should not be used it is designed to be ran in manuals that use atm fluid use there gear oil for other applications i thought we all used extra s in subarus anyway??

[BAC5.2]

you just thinned out the mix. that makes it easier to squeeze the oil out from between the synchro rings and the cone on the side of the gears. the grooves on the inside of your synchro rings are probably dull. thinning the oil just makes it easier for them to function despite being worn.

 

That's not how a synchro is designed to work, but that's similar to what synchromesh will do. A synchro is designed to operate on the principle of hydrostatic pressure. Working properly, the balk ring should never touch the cone metal-to-metal. The shear properties of the fluid are what make the synchro work, not metal-to-metal friction. Synchromesh shears easily, and does allow metal-to-metal contact. You get the impression that you are making the synchros work "better", when you are simply accelerating their wear ultimately ensuring you will need to rebuild the trans.

 

You can pull a trans apart that has 200k on it, and has synchros that look brand new. I know, because I've done just that.

[El Capitan]

Hi. I have 2007 subaru outback sedan 3.0 H6,with 5AT.I want to change oil in both diffs.In owners manual there is written that it needs oil 75w90 GL-5.

The only problem is that I live in Europe,Georgia and here is only Motul gear 300 and Motul gear 300 LS.Motul gear 300 is GL-4/5,and gear300LS is GL-5,bat it has LS additives.please I need advise,which fluid is better and can I use this GL-5 LSD in my front or rear diff? Thank you.

[MiniStiGuy]

Sooo Just put Motul 300 in everything is what I got out of reading all this...

[Impatient]

Redline told me not to use Shockproof if not racing. I suppose I could have pressed harder why SP was good for racing and not DD, but cold flow was his concern, and of course he wasn't going to comment on a cross-brand cocktail. But he recommended against mixing RL shockproof with RL 75-90 ns, so I dropped it. I'm sure Bac's cocktail works, but if something goes wrong in my DD, I doubt he can come to the rescue during a 3rd party warranty claim. Actually, if the Delvac or Extra-S were available locally, that might change my mind. So far, royal purple and lower-low end (not even SuperTech) are only non-ls I have found in stores. I can't believe the dealer won't sell me some Extra-S. Heck, they can't even tell me what they put in last time.

[bugblatterbeast]

thanks for clarifying that. you cleared up a related lingering question I've had for years. I always wondered how it was possible for a gear box to feel smooth during a shift if the synchro rings actually made contact with the cone. I always assumed as there would be some sticking action at zero speed difference (cone to ring) that would prevent the synchro sleeve from sliding past the rings and engaging the features on the gear (just below the cone... not sure what the little teeth are called formally). I guess the lack of metal to metal contact is what does it. I was always puzzled by how a gear box can not feel "crunchy" during the last bit of a shift when the speed difference is zero but the synchro ring is still rotated slightly out of alignment with the little teeth just below the cone.

 

is this how adding shockproof to the mix helps? the solids increase the effective viscosity of the gear oil under shear while not increasing it so much at low to zero shear?

 

 

That's not how a synchro is designed to work, but that's similar to what synchromesh will do. A synchro is designed to operate on the principle of hydrostatic pressure. Working properly, the balk ring should never touch the cone metal-to-metal. The shear properties of the fluid are what make the synchro work, not metal-to-metal friction. Synchromesh shears easily, and does allow metal-to-metal contact. You get the impression that you are making the synchros work "better", when you are simply accelerating their wear ultimately ensuring you will need to rebuild the trans.

 

You can pull a trans apart that has 200k on it, and has synchros that look brand new. I know, because I've done just that.

[apexi]

This is the most recent transmission fluid thread I can find, so I just wanted to throw out this out there after having Red Line 75w-90NS in my transmission for 2 days and a couple hundred miles.

 

Car has 130k, I've run Extra-S, amsoil severe gear 75w-90, supertech synthetic blend 75w-90, and I just recently put Red Line 75w-90NS in the transmission.

 

I can't remember much about extra-s or amsoil SVG, so here are my thoughts on Red line NS vs supertech syn blend.

 

-The car doesn't shift very smoothly anymore. There has been a noticeable increase in effort required to change gears. What this also means is that it's slightly more difficult to shift fast. One of the "problems" I had with supertech was that if I tried to shift too fast (and I mean way to fast), my gearbox would crunch/grind. With the red line it isn't even possible for me to try and shift that fast anymore, so I guess I couldn't replicate the problem if i tried. Now, I'm reluctant to call this a bad thing. Some manual cars I've driven like hondas, acuras, all are able to shift very quickly and smoothly. If my memory serves me right, some other manual cars like a 3-series bmw and infinity g35 just naturally didn't shift very nice in my opinion. I'd put my legacy in the middle of the spectrum somewhere, not silky smooth, but not terrible either. If 1 was very smooth, and 10 was clunky, I'd say the car went from a 3 with supertech or so to a 6 with Red Line.

 

-I'm reluctant to say this, but it honestly is something I have noticed. When I first try to get going in 1st gear, the car seems to bog a bit, almost like mild turbo lag even though I don't have a turbo. For some odd reason, I think it only happens when going from reverse to 1st. Next time I go out I'll try to see if it happens going to 1st from a standstill. I was reluctant to say this because I don't know if it's even possible for a fluid change to do this, in the back of my head I wonder if the lack of friction modifiers could be doing this. A more realistic reason would be the weather, since temperatures here in CT are finally rising and maybe my car's ECU hasn't fully adjusted. But it'd be quite coincidental that I started to notice it after changing the fluid, though I guess most people tend to be more observant of how their cars act after they change something.

 

I wanted to give the red line a shot because I don't like changing my transmission fluid, and I wanted to run an oil that I'd feel comfortable leaving in for longer than my usual 20k-30k. I do a lot of driving, so it'd be nice to change it every other year vs every year, though at the end of the day changing the fluid once a year isn't that big of a deal. I know that BAC5.2 didn't like NS, but his review was really one of the only negative ones that I could find. I did see a number of positive NS reviews from subaru owners on other message boards, so I decided to give it a try and see what happens. I regret putting it in since it I don't like the extra effort required to shift, it doesn't grind or anything (yet.. fingers crossed), it just doesn't glide into gear anymore. For all I know, this could be a good thing, this could be better for the syncros, I don't know enough about transmissions to say. Either way, I'm kind of bummed that I spent $60 on fluid that I don't really like, but I'm trying to be positive in thinking that at least I've got a solid gear oil in my transmission even though the feel is different. I might e-mail red line for kicks later and ask them about the "bogging" in 1st (and sometimes 2nd I think, I forget), as well as the mild extra effort to change gears.

[BAC5.2]

I know that BAC5.2 didn't like NS... I regret putting it in.

 

So what have we learned?

[apexi]

Listen to Bac!

[Impatient]

So what have we learned?

 

That Subaru's are a P-I-T-A.

 

I wanted to give the red line a shot because I don't like changing my transmission fluid, and I wanted to run an oil that I'd feel comfortable leaving in for longer than my usual 20k-30k.

 

Sounds like a worthwhile goal.

 

Not to make BAC's head swell any larger , but I was about to go the RL NS route myself until I stumbled on his post in the Forester blog (from probably 2009?? BTW, love that Forester avatar). As a result, I changed my mind, bought some Motul. But, you got RL themselves saying not to use Shockproof, not even to mix it in with the NS, so it is a bit confusing. Bac's creds are...???...maybe known to a few, but he "could" be just as big a crank as the DS1 guy he flamed. And his audience might be....racers, not DD's. Anyway, assuming things work out better for me than apexi, a reluctant thanks to Bac...though 100% Motul isn't really his advice either...I just wanted to get as close to nirvana as possible without cross-brand mixing.

 

Well, here is something else I learned. I haven't had time to do the swap, so I figured I would "top off" the transmission. The L and F marks on the dipstick appear to be less than 0.2 Liter (< 0.2 qt...less than 1/5 qt) apart....unless that dipstick is as unreliable as the engine oil one is. Like I said: P-I-T-A.

 

It doesn't help that the dealers around here think its OK to charge $600 plus for a 60K service but can't tell you what the fluid is in the bulk drum they use. Points for them that they had at least heard of Extra-S, even if they won't sell it, and don't use it.

 

Now the question is: After the top-off, I don't have enough Motul to do a 100% swap in the rear diff and transmission, so do I buy 1 quart of Shockproof, to mix with 2.8qt of Motul in the tranny, or do I stick to my pre-conception and not mix? I mean is a little shockproof better than no shockproof?? I do have a slight notchiness/reluctance to the shifting, yet want best possible fuel economy in typical 10 mile stop-n-go commutes....not in Minnesota climate, but not instantly at normal operating temps either. Again, I don't want to compromise refill intervals, and expect 30K+ from the Motul.

[Impatient]

So what have we learned?

 

Further, Subaru recommends GL5. I venture to guess there are plenty of GL5 fluids that are worse than RL NS. What about Mobil 1, Valvoline, Castrol, Penzoil, etc, etc, that have friction mod's. And then there are SuperTech, Coastal, and Master Pro without FM's. How do they stack up? I mean, it is actually hard to find a GL5 fluid without the LS friction mods. What if apexi had taken the car to his dealer, and they had filled his transmission with Valvoline SynPower. Better or worse? What, other than BAC's opinion, clues us in that NS is "terrible." Amsoil's 2007 test??? NS was better than many in that test.

[Nolmers06LGT]

Now the question is: After the top-off, I don't have enough Motul to do a 100% swap in the rear diff and transmission, so do I buy 1 quart of Shockproof, to mix with 2.8qt of Motul in the tranny, or do I stick to my pre-conception and not mix? I mean is a little shockproof better than no shockproof?? I do have a slight notchiness/reluctance to the shifting, yet want best possible fuel economy in typical 10 mile stop-n-go commutes....not in Minnesota climate, but not instantly at normal operating temps either. Again, I don't want to compromise refill intervals, and expect 30K+ from the Motul.

 

I ran straight motul in my 5mt for 10k before I swapped to the cocktail BAC suggested. The straight Motul was too thin for the synchros. After switching to the cocktail, my car is noticeably smoother.

 

As for BAC's credibility, If you've read enough posts from BAC you'll learn to trust him.

[BAC5.2]

you got RL themselves saying not to use Shockproof, not even to mix it in with the NS, so it is a bit confusing...

 

I'm not sure what's so confusing about it. Redline designed the fluid for gearboxes that saw high loads. They wanted high film thickness and low viscosity, and the ability to mitigate impact loads at gear surfaces. Whether they intended to or not, the properties of Shockproof fit within the criteria of MIL-STD 2105D and are subsequently allowable as an API GL-5 fluid should RL decide to pay the API to use their sticker. Back in the early 2000's, they said "not recommended for most syncro-type transmissions". If you read their white papers, and any other current documentation, you'll find they now reserve those comments for heavyweight only. And their reasoning for not recommending it was "it's too slippery". Since I've already explained how synchros work, you can see that the concern is unjustified.

 

Bac's creds are...???...

 

More than a decade in the Subaru world, more than 5 years working at one of the most highly regarded Subaru transmission shops in the country, a BS and an MS in mechanical engineering, a fair bit of experience in gearbox design, and quite a long history of success with the shockproof/motul combo.

 

Why would I make recommendations to a target audience of racers, by suggesting the combo to owners of Foresters and Legacys?

 

Now the question is: After the top-off, I don't have enough Motul to do a 100% swap in the rear diff and transmission, so do I buy 1 quart of Shockproof, to mix with 2.8qt of Motul in the tranny, or do I stick to my pre-conception and not mix? I mean is a little shockproof better than no shockproof?? I do have a slight notchiness/reluctance to the shifting, yet want best possible fuel economy in typical 10 mile stop-n-go commutes....not in Minnesota climate, but not instantly at normal operating temps either. Again, I don't want to compromise refill intervals, and expect 30K+ from the Motul.

 

Since you don't seem to care about, or respect, my opinion I'd suggest to anyone else with a similar situation to run straight Motul in the rear diff and top off the trans with Shockproof.

 

I'd also suggest the ignorance of expecting any replacement interval. You can expect all day long, but contamination happens regardless. You should be inspecting trans fluid every other oil change for fill-level and quality. If it needs replacing, replace it. $60-90 in fluid every 15k is a small price to pay to protect a rather significant investment. You wouldn't treat your engine oil the same way, would you?

 

Further, Subaru recommends GL5. I venture to guess there are plenty of GL5 fluids that are worse than RL NS. What about Mobil 1, Valvoline, Castrol, Penzoil, etc, etc, that have friction mod's. And then there are SuperTech, Coastal, and Master Pro without FM's. How do they stack up? I mean, it is actually hard to find a GL5 fluid without the LS friction mods. What if apexi had taken the car to his dealer, and they had filled his transmission with Valvoline SynPower. Better or worse? What, other than BAC's opinion, clues us in that NS is "terrible." Amsoil's 2007 test??? NS was better than many in that test.

 

You don't have to follow my advice, or heed my warnings. You are perfectly free to attempt to duplicate my experience on your own. I've put more than 200k on the Shockproof/Motul mix in my various cars over the years.

 

Just like engine oil, you go with what works. It has been my overwhelming experience that Redline's 75W90NS is terrible. I've used it in my own car, based on great reviews and it being "the right stuff". Within 3k it was getting hard to shift, after 10k it was grinding into every gear, and at 20k the trans was blown. I've seen similar experience with Royal Purple though I never ran it in a vehicle I owned. I went Shockproof/Motul, and never looked back. I think you'll find that most people who make that switch will feel the same way.