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Thank you @zumata for your help . Actually grab hold of motorcraft is again a PITA here in Italy as many mx5 members complain . I have purchased amsoil via a German seller and purchased castrol syntrax 75w90 for the differential . Thanx a lot for you inputs !!!
 

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Update on my previous post. Synchromesh fluids do have extreme pressure additives. I should have figured, since they're recommended in so many truck NV transmissions where extreme pressure is the norm. They simply don't have high levels of sulfur, which is one of the requirements for GL-4 and GL-5 ratings, and why they don't carry the GL-4 rating on the bottle.

That's not to say they can't handle shock loads, aggressive driving, and extreme temperatures.

It's also worth noting that higher GL ratings are typically added to manual transmission fluids when the OEM fluid is particularly thin. On thicker fluids, the film strength takes the place of some of those EP additives.

IMO you'd be fine with spirited driving and your occasional auto-x event, but if you were road racing frequently or changing tires more often than socks, you should probably look at the 75W-90 GL-4 instead.
Hey XR, I'm thinking of going back to Synchromesh. It just feels better than 75W-90 in every way. It's smooth both warm or cold and reduces transmission noise significantly. Even on the track it feels slightly more willing to shift.

You said that 75W-90 is recommended over Synchromesh for racing use, why is that? Does it have something do do with the sulfur content and what exactly does sulfur do?
 

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Discussion Starter #83
Hey XR, I'm thinking of going back to Synchromesh. It just feels better than 75W-90 in every way. It's smooth both warm or cold and reduces transmission noise significantly. Even on the track it feels slightly more willing to shift.

You said that 75W-90 is recommended over Synchromesh for racing use, why is that? Does it have something do do with the sulfur content and what exactly does sulfur do?
Just a higher EP additive concentration, which isn't really a big factor in manual transmissions. I'm going to try blending one quart of 75W-90 with the rest synchromesh on my next change.

I don't have any transmission noise. What kind are you referring to?

Sounds like our transmissions really don't get that hot.

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Just a higher EP additive concentration, which isn't really a big factor in manual transmissions. I'm going to try blending one quart of 75W-90 with the rest synchromesh on my next change.

I don't have any transmission noise. What kind are you referring to?
So would you say straight synchromesh is okay for racing use then? I don’t see much talk about it in racing circles, don’t know why it’s not used more. Like you said before the thickness of synchromesh should compensate for the lack of EP additives should it not?
The noise I’m referring to is a fidget spinner-like noise. It was much louder when I was on the OEM fluid, sounded like 20 fidget spinners spinning at once, now it’s more like 1 or 2. The noise went away completely when I switched to synchromesh.
 

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Discussion Starter #85
So would you say straight synchromesh is okay for racing use then? I don’t see much talk about it in racing circles, don’t know why it’s not used more. Like you said before the thickness of synchromesh should compensate for the lack of EP additives should it not?
The noise I’m referring to is a fidget spinner-like noise. It was much louder when I was on the OEM fluid, sounded like 20 fidget spinners spinning at once, now it’s more like 1 or 2. The noise went away completely when I switched to synchromesh.
Ah, that makes sense. I do think the higher viscosity would compensate for the EP additive difference and it's not like synchromesh doesn't have any anti-wear additives of its own. I personally think it would be fine. Manual transmissions don't really see that much pressure compared to differentials. I mean we spec Synchromesh for some 3500 truck NV transmissions.

The fidget spinner sound would be the synchros. Definitely better not to hear those whining, I think. Sounds like Synchromesh has a better friction modifier package for these transmissions.

How often are you changing it?

BTW, reason I mention blending is there's a transmission builder out in the Mustang community that actually recommends two quarts of AMSOIL Synchromesh blended with a quart of AMSOIL 75W-90 GL-4 in those transmissions. I get requests quotes for it all the time and it's their go-to transmission fluid blend. Calimer is the name of the shop and everyone calls it the "Calimer cocktail." Obviously not something AMSOIL recommends so this as well as the other two AMSOIL products should be used at your discretion. I use the 75W-90 simply because that's what AMSOIL recommended for the NC Miata and it's the same transmission.

In the spring, I'll be blending in 1.2 quarts Synchromesh with a quart of the 75W-90 GL-4.

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So would you say straight synchromesh is okay for racing use then? I don’t see much talk about it in racing circles, don’t know why it’s not used more. Like you said before the thickness of synchromesh should compensate for the lack of EP additives should it not?
The noise I’m referring to is a fidget spinner-like noise. It was much louder when I was on the OEM fluid, sounded like 20 fidget spinners spinning at once, now it’s more like 1 or 2. The noise went away completely when I switched to synchromesh.
I've tried them both on the track and had no issues either way. I'm currently on the 75W-90 and I think I like it better than Syncromesh for both track and daily driving. We'll see how it does as the temps drop, though. Your temps are much colder than mine.
 

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Discussion Starter #87
I've tried them both on the track and had no issues either way. I'm currently on the 75W-90 and I think I like it better than Syncromesh for both track and daily driving. We'll see how it does as the temps drop, though. Your temps are much colder than mine.
You know, I think transmission break-in will also have an effect here. The transmission seems to be a bit more finicky with fluids until you put a good 7500 miles on it. After that, it doesn't seem to care as much. I've been running the 75W-90 GL-4 as low as 35F lately, and I'll admit it's a bit stiff going into gears the first few times, and by few I literally mean 3-4 shifts, but after that I don't notice it anymore and completely forget the transmission is cold. The only gear that ever fights me is downshifting into 1st. I also rev match and double clutch on down shifts (1st is a bit harder to do).
 

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You know, I think transmission break-in will also have an effect here. The transmission seems to be a bit more finicky with fluids until you put a good 7500 miles on it. After that, it doesn't seem to care as much. I've been running the 75W-90 GL-4 as low as 35F lately, and I'll admit it's a bit stiff going into gears the first few times, and by few I literally mean 3-4 shifts, but after that I don't notice it anymore and completely forget the transmission is cold. The only gear that ever fights me is downshifting into 1st. I also rev match and double clutch on down shifts (1st is a bit harder to do).
I have almost 12,000 miles on my car now but I've never had any issues with the transmission. I guess I've driven so many poor manual cars in the past that this one feels like a dream. I'm extremely happy with the Amsoil fluids I have in my car and don't plan on changing anything. I don't notice a rough shift into first but if one gear has to fight you, you want it to be first. Less chance of a money shift I guess.
 

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You know, I think transmission break-in will also have an effect here. The transmission seems to be a bit more finicky with fluids until you put a good 7500 miles on it. After that, it doesn't seem to care as much. I've been running the 75W-90 GL-4 as low as 35F lately, and I'll admit it's a bit stiff going into gears the first few times, and by few I literally mean 3-4 shifts, but after that I don't notice it anymore and completely forget the transmission is cold. The only gear that ever fights me is downshifting into 1st. I also rev match and double clutch on down shifts (1st is a bit harder to do).
This has been exactly my experience with 75W-90. Synchromesh on the other hand worked like a dream at these freezing temps. I think I will try Synchromesh again next year. So far I haven't been able to find any examples of transmission failures due to use of Synchromesh for racing and I don't see why it can't be used. If there is any kind of problem I guess I'll find out the hard way like I always have, lol!

By the way do you know what the viscosity vs temperature profiles look like for the two fluids? Is Synchromesh thinner than 75W-90 at cold temps and thicker than it at high temps?
 

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Discussion Starter #90
This has been exactly my experience with 75W-90. Synchromesh on the other hand worked like a dream at these freezing temps. I think I will try Synchromesh again next year. So far I haven't been able to find any examples of transmission failures due to use of Synchromesh for racing and I don't see why it can't be used. If there is any kind of problem I guess I'll find out the hard way like I always have, lol!

By the way do you know what the viscosity vs temperature profiles look like for the two fluids? Is Synchromesh thinner than 75W-90 at cold temps and thicker than it at high temps?
Honestly I haven't seen a failure with Synchromesh anywhere. There are thousands of Cruze owners running it in the GM M32 transmission, a number of 124 Spider owners here, countless Honda owners, and in the 6 years I've been a dealer, I haven't heard of one single transmission issue or failure running it. I think we're probably over-thinking the lubrication requirements of these transmissions.

Viscosity curves are a bit difficult to predict but we have some limited information.

75W-90 GL-4:
100C: 14 cSt
40C: 80.3 cSt
Brookfield -40C: 28,425 cP
Pour point: -69F
Viscosity Index: 181

Synchromesh:
100C: 10.1
40C: 49.4
Brookfield -40C: 32,000 cP
Pour point: -54F
Viscosity Index: 196

From this information, 75W-90 GL-4 actually performs better at -40C than Synchromesh does, which means somewhere in the negative digits, the viscosity curves would cross. These are nonlinear viscosity curves.

Curiously enough (and I literally JUST noticed this), both fluids have the same 4-ball wear scar at 0.40mm using the Shell 4-ball extreme pressure wear test (ASTM D4172), and it seems the biggest difference between them is suitability in what AMSOIL refers to as "shock-loading conditions," present in towing and hauling.
 

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Honestly I haven't seen a failure with Synchromesh anywhere. There are thousands of Cruze owners running it in the GM M32 transmission, a number of 124 Spider owners here, countless Honda owners, and in the 6 years I've been a dealer, I haven't heard of one single transmission issue or failure running it. I think we're probably over-thinking the lubrication requirements of these transmissions.

Viscosity curves are a bit difficult to predict but we have some limited information.

75W-90 GL-4:
100C: 14 cSt
40C: 80.3 cSt
Brookfield -40C: 28,425 cP
Pour point: -69F
Viscosity Index: 181

Synchromesh:
100C: 10.1
40C: 49.4
Brookfield -40C: 32,000 cP
Pour point: -54F
Viscosity Index: 196

From this information, 75W-90 GL-4 actually performs better at -40C than Synchromesh does, which means somewhere in the negative digits, the viscosity curves would cross. These are nonlinear viscosity curves.

Curiously enough (and I literally JUST noticed this), both fluids have the same 4-ball wear scar at 0.40mm using the Shell 4-ball extreme pressure wear test (ASTM D4172), and it seems the biggest difference between them is suitability in what AMSOIL refers to as "shock-loading conditions," present in towing and hauling.
Thanks for the great info XR. So is this data saying that between 40C and 100C, Synchromesh is less viscous than 75W-90?
 

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Discussion Starter #92
Thanks for the great info XR. So is this data saying that between 40C and 100C, Synchromesh is less viscous than 75W-90?
Yep. It's a lower viscosity fluid, which is why it performs better in cold weather. I'd guess the cross point where both fluids have the same viscosity will be somewhere around -25C.

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Yep. It's a lower viscosity fluid, which is why it performs better in cold weather. I'd guess the cross point where both fluids have the same viscosity will be somewhere around -25C.
Okay, I think I misunderstood your earlier statement about the viscosity of Synchromesh. I thought you said Synchromesh is thicker than 75W-90 so it can be used with less EP additives but maybe all you meant was Synchromesh is viscous enough to be used with less additives but it's not necessarily more viscous than 75W-90. So I guess even though Synchromesh will do fine on the track, 75W-90 is still the better option.
 

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Discussion Starter #94
Okay, I think I misunderstood your earlier statement about the viscosity of Synchromesh. I thought you said Synchromesh is thicker than 75W-90 so it can be used with less EP additives but maybe all you meant was Synchromesh is viscous enough to be used with less additives but it's not necessarily more viscous than 75W-90. So I guess even though Synchromesh will do fine on the track, 75W-90 is still the better option.
Synchromesh seems to be thicker than the OEM fluid, which is also GL-4 rated. That's what I was getting at.

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Ok folks, I seem to have gotten confused. Do I just use Amsoil Synchromesh only or do I have to use an additive also for my Abarth? As it has a LSD. Any help would be appreciated as I'd like to attempt the fluid change soon. Thanks for all the good information!
 

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Discussion Starter #96
Ok folks, I seem to have gotten confused. Do I just use Amsoil Synchromesh only or do I have to use an additive also for my Abarth? As it has a LSD. Any help would be appreciated as I'd like to attempt the fluid change soon. Thanks for all the good information!
Synchromesh is a manual transmission fluid. The LSD is in the back, in the differential. Two completely separate components that use separate fluids.

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I was looking at the NC trans fluid swap from revlimiter and it mentions shifter turret fluid - have you topped yours off or changed it when you did the trans fluid?
 

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I was looking at the NC trans fluid swap from revlimiter and it mentions shifter turret fluid - have you topped yours off or changed it when you did the trans fluid?
Good question.
manual gear shift lever lube, and more

I'm waiting for spring weather to actually arrive, then I'll be tearing into my gear shifter to replace the bushing talked about later in that thread I linked.

Steve.
 

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Good question.
manual gear shift lever lube, and more

I'm waiting for spring weather to actually arrive, then I'll be tearing into my gear shifter to replace the bushing talked about later in that thread I linked.

Steve.
Can confirm the shifter bushing is plastic.

I just checked my turret, seems to hold different from the trans - mine was filled to the level and lubricated so I didn't change anything at this time on the turret area.

Just ordered a bronze shifter bushing from Fab9 tuning for the NC3 MX5 :)
 

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Can confirm the shifter bushing is plastic.

I just checked my turret, seems to hold different from the trans - mine was filled to the level and lubricated so I didn't change anything at this time on the turret area.

Just ordered a bronze shifter bushing from Fab9 tuning for the NC3 MX5 :)
Did you order the larger 24mm bushing?

Any advice on dismantling the console and shifter assembly?

Steve.
 
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