Positive Gearbox Oil Experience

donwells · 28 August 2015

I changed my Gearbox oil to the GM Synchromesh 1/3, 2/3 cocktail and can't believe the difference. After draining the old oil into a clean pan, I felt through it for signs of metal or anything else and commented to myself that whatever I put back in the gearbox could not be any slicker, but man was I wrong. After installing the new oil and taking the car out for a spin, I could not believe ho much easier it was to shift in every direction and at any speeds. The stuff is magic!

If you have not done it, do it. The most significant upgrades for the money I've made.

jwmelvin · 28 August 2015

Thanks for the report. It makes me want to try it.

RYU · 28 August 2015

The problem with synchromesh or other friction modifiers is how it affects the LSD. The NSX is basically a fwd car where the LSD shares the oil as the rest of the trans.

most people won't notice much reduction of LSD performance in street driving.

jwmelvin · 28 August 2015

Its always been unclear to me to what extent the effect on the LSD depends on which year car we are talking about. The later (97+?) cars have a different LSD than the earlier ones.

michaelbrat · 28 August 2015

Is it possible that it affects the clutch too? I know this is a problem with motorcycles that use the engine oil for everything. Using "high mileage" or "eco" motor oils proves to be too slick and impairs clutch engagement.

Mike B

Wavey1 · 28 August 2015

michaelbrat said:
Is it possible that it affects the clutch too? I know this is a problem with motorcycles that use the engine oil for everything. Using "high mileage" or "eco" motor oils proves to be too slick and impairs clutch engagement.

Mike B

No, those are "wet clutches", where the clutch plates operate in the gearbox oil.

BATMANs · 28 August 2015

Funny how the GM guys have moved to this:

http://www.amsoil.com/shop/by-produ.../manual-synchromesh-transmission-fluid-5w-30/

And it shifts better, etc.

I'm running this in the NSX and it's that good.

Honcho · 28 August 2015

RYU said:
The problem with synchromesh or other friction modifiers is how it affects the LSD. The NSX is basically a fwd car where the LSD shares the oil as the rest of the trans.

most people won't notice much reduction of LSD performance in street driving.

This. The NSX limited slip differential is a wet-clutch type, which means that there is a stack of clutch plates that are constantly bathed in oil as the differential spins. This oil is shared with the rest of the transmission. As the clutch pack engages and disengages, the discs have a certain amount of designed slip to lock and unlock the left and right axles. Problem is only Honda knows the material properties and friction characteristics of the clutch plates. According to them, the only two fluids that will not adversely affect LSD clutch engagement are 5W-30 motor oil and Honda genuine trans fluid. This doesn't mean other fluids won't work, just that Honda never tested them in the NSX differential. So, you're kind of experimenting on your very expensive transmission if you use anything else. You run the risk of wearing out the clutch plates and losing LSD function, effectively turning the transaxle into an open differential. Practically speaking, 99% of NSX owners will never notice the difference on the street, but anyone who tracks their car will be making a sad panda face. Traction coming out of a corner will be greatly reduced. This is why my NSX was always fed Honda White Cap and she always was hot coming out of the turns.

The King · 29 August 2015

Honcho said:
This. The NSX limited slip differential is a wet-clutch type, which means that there is a stack of clutch plates that are constantly bathed in oil as the differential spins. This oil is shared with the rest of the transmission. As the clutch pack engages and disengages, the discs have a certain amount of designed slip to lock and unlock the left and right axles. Problem is only Honda knows the material properties and friction characteristics of the clutch plates. According to them, the only two fluids that will not adversely affect LSD clutch engagement are 5W-30 motor oil and Honda genuine trans fluid. This doesn't mean other fluids won't work, just that Honda never tested them in the NSX differential. So, you're kind of experimenting on your very expensive transmission if you use anything else. You run the risk of wearing out the clutch plates and losing LSD function, effectively turning the transaxle into an open differential. Practically speaking, 99% of NSX owners will never notice the difference on the street, but anyone who tracks their car will be making a sad panda face. Traction coming out of a corner will be greatly reduced. This is why my NSX was always fed Honda White Cap and she always was hot coming out of the turns.

I don't think my car sees the same useage as Honcho's but my transmisson seems to work fine so I'll probably just continue using what Honda suggests.

jwmelvin · 29 August 2015

Honcho said:
You run the risk of wearing out the clutch plates and losing LSD function, effectively turning the transaxle into an open differential.

These two statements do not generally go together. Better lubrication (i.e., that which reduces friction) reduces wear; this is tribology. So while there may be increased relative motion, it is a stretch to say that will wear out the clutch plates. Moreover, there is no reason to assert that a change in friction effectively turns the differential into an open diff. Are you contending that the GM fluid results in zero friction between the plates?

Are you confident that even your assumptions are true for both of the LSDs that Honda used? I'm not asserting otherwise but like I said, I've never been clear on the precise differences between the two configurations.

Honcho said:
...anyone who tracks their car will be making a sad panda face. Traction coming out of a corner will be greatly reduced.

This is statements of degree without any support. Didn't you say that you have not tried this and that it would be an experiment?

I remember statements on Prime asserting that the GM fluid could cause some irreversible change to the LSD (i.e., permanently changing the friction of the plates). I find that even more unsupported and contrary to science. But I would enjoy being corrected with either evidence or sound theory.

Mac Attack · 29 August 2015

Yes, these "Which is the best oil" debates are fun.

Instead of speculating, why don't people measure their specific breakaway torque? While not the true test (temperature and dynamic friction), it will at least put some of this LSD impact to bed. It's not hard folks, look at page 15-4 of the SM.

Also, if people are that into their LSD performance for the track, then they should consider a transmission cooler for repeatable performance.

Personally, my '92 with OEM LSD had about 60k miles on the old Honda MTF, then I switched over to the GM synchromesh cocktail for about 30k miles.

After that, I went with the Amsoil stuff Batmans linked (even though it says not to use on wet clutch packs) for another 30k miles without any negative effects.

Now, I am back on Honda white cap MTF and it feels the same as the Amsoil stuff.

I'm not too concerned.

Dave

darock · 30 August 2015

I think, the biggest issue comes from people filling a totally wrong gearbox oil like it happened on my car. It was one of those stinky GL5 oils. Probably some castol crap. The gearbox was horrible and even had grinding from second to third.

Put in MTF3 from Honda and it instantly worked perfectly again. Did take some miles but even the grinding is gone now. Its also a lot quieter again. The LSD works more seamlessly and stopped making clicking noise when U turning.

Bernhard

jwmelvin · 30 August 2015

Mac Attack said:
... I switched over to the GM synchromesh cocktail for about 30k miles.

Did you notice any benefit to shifting smoothness or detriment to LSD performance with the GM cocktail?

RYU · 30 August 2015

Happy to change my mind with some credible performance data. I just don't know any better and my small brain tells me to stick with what Honda recommends unless proven otherwise.

I did try the "cocktail" in my previous S2000. It makes it smoother shifting, yes.

With that said, my JDM 5spd was recently rebuilt by Jon Martin. New synchros, etc... Honda recommended MTF and after about 1000 miles it's silky smooth in shifting. It was a bit notchy and tough going into first in the beginning.

ftuhy · 30 August 2015

Honda moved away from the ATF because of wear problems to their MTF and the '96 shop manual supplement clearly states that. However, even in 80 or 90F weather, my car still doesn't downshift easily into 1st (even in plain old easy-going street driving) until the car is fully warmed up (like RYU's experience). However, there's no problem up or down shifting into any other gears. If the GM cocktail fixes that problem, to me it would be worth the switch.

Mac Attack · 30 August 2015

jwmelvin said:
Did you notice any benefit to shifting smoothness or detriment to LSD performance with the GM cocktail?

Much better shifting smoothness with a small-to-negligible decrease in LSD performance with the GM cocktail over the Honda white-cap MTF.

The shifting smoothness made it worth it.

I rebuilt my tranny for the preventative snap ring fix at the 90k mark. While "in there," I had new synchros and bearings installed. I did not take apart the differential to check the clutch packs. After the rebuild I went straight to the Amsoil MTF and it shifts like butter. Never measured the diff break-away torque.

HDA · 31 August 2015

To the Op, it also depends how old was your trans fluid. If you are coming from a 50k Honda MtF them most likely any new fresh fluid will make a difference.

I am very, very lazy and like to stick to what mama Honda days.

Honcho · 31 August 2015

jwmelvin said:
These two statements do not generally go together. Better lubrication (i.e., that which reduces friction) reduces wear; this is tribology. So while there may be increased relative motion, it is a stretch to say that will wear out the clutch plates. Moreover, there is no reason to assert that a change in friction effectively turns the differential into an open diff. Are you contending that the GM fluid results in zero friction between the plates?

Are you confident that even your assumptions are true for both of the LSDs that Honda used? I'm not asserting otherwise but like I said, I've never been clear on the precise differences between the two configurations.

This is statements of degree without any support. Didn't you say that you have not tried this and that it would be an experiment?

I remember statements on Prime asserting that the GM fluid could cause some irreversible change to the LSD (i.e., permanently changing the friction of the plates). I find that even more unsupported and contrary to science. But I would enjoy being corrected with either evidence or sound theory.

I will just say what the great LarryB said to me: Hey, it's your transmission. Use whatever you want

That said, Honda White Cap was great in my 5-speed and shifting was very smooth- even in sub zero conditions.

robbiedawg · 31 August 2015

Honcho said:
I will just say what the great LarryB said to me: Hey, it's your transmission. Use whatever you want That said, Honda White Cap was great in my 5-speed and shifting was very smooth- even in sub zero conditions.

i take it that larryb was recommending the white cap then...

Larry Bastanza · 31 August 2015

My recommendation for the 5 speed, White Cap.

I have used the GM cocktail for the 6 speed, and it has a major difference for the better. The dual syncros in the 6 speed work so much better with the GM syncromesh. I have not used this on track cars, only street usage NSX's and ever person comes back and thinks I rebuild the trans for them

.....

Regards,
LarryB

robbiedawg · 31 August 2015

thanks larry,why don't you recommend the gm cocktail for the 5-speed?

Larry Bastanza · 31 August 2015

No need, they shift fine with the White Cap........... the 5 speeds have single syncro's and work fine with the OEM fluid in my experience. You know, "if it ain't broke.........."

Regards,
LarryB

jwmelvin · 31 August 2015

Thanks for the further info Larry. Do you have any experience with or reports of degraded LSD performance with the GM cocktail in the 6-speeds?

Larry Bastanza · 31 August 2015

No, and again as stated above this does not appear to be an issue with typical street driven cars. I have not used it in any track prepped car w/6 speed.

Honcho · 31 August 2015

robbiedawg said:
i take it that larryb was recommending the white cap then...

Larry already answered but yes, he was recommending the white cap fluid. He rebuilt my 5-speed with JDM gears and NSX-R diff. I was asking about the different fluid options. Wow, now that I think about it that was way back in 2009-10!!

Positive Gearbox Oil Experience

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