Transmission fluid swap?

[getbent]

I'm using the MT-90 in my Mazdaspeed6 and its done pretty well but at ~20K miles its gotten noticably notchier.

[Zoomie]

Motul only.

[Heero]

So has anyone done a change after the break in period?

I'm picking up my BRZ soon & the first things I will be doing is Oil change after 1000KMs and then again after another 1000KMs. Regular changes after that.

But I would also like to flush and change gear oil after 1000 or 2000km too.

[Jeff Lange]

Toyota lists "TOYOTA Genuine MG Gear Oil Special II, API GL-3, SAE 75W90" for it. Can't say I've dealt with that too much in the past.

Jeff

[rice_classic]

I like Amsoil products myself... just not in my transmission. Now I'm from a Honda background and do production racing. I found that no synthetic worked in my transmission (D-Series tranny). Amsoil Synchromesh, Redline MT or Redline MT90. They were too slippery for the synchros and I would crunch gears at speed (on a freshly rebuilt trans). I switch to Penzoil Synchromesh or Honda MTF or SAE 30 and all was good again. I also use the Pennzoil stuff in my street cars with one exception. When I had my S2000 I used the OEM Honda MTF in my transmission and after 60k miles and some hard driving I never had a single "crunch".

Some of the S2k folks around here run 1/2 MT90 and 1/2 Honda MTF in their S2ks, others use all amsoil, redline, torco or Pennzoil. It seems like the S2k Box and it's shift collars and synchros aren't as sensitive to synthetics.

The D-Series boxes are super sensitive. No Syn in a D box.. no no.

[rice_classic]

Anyone who mentions GM Synchromesh... It's the identical fluid to the Pennzoil.

So if someone tells you to try the GM Synchromesh and you don't want to go down to a GM dealership then just go to Autozone and pick up this:

[Bristecom]

I did a lot of research on this a few years back. I even talked to oil experts from Shell/Pennzoil and Mobil 1 about it. There are some important things to understand:

The main difference between the GL ratings is the amount of extreme pressure agents (EP) they have. Extreme pressure agents contain sulfer-phosphorus compounds which are corrosive to yellow metals such as copper, brass, and bronze which are often found in synchronizers. However, extreme pressure agents only activate during extreme pressures. So even though GL-3 oils contain EP, it is in a small enough amount that it will not corrode the metals under normal conditions. In other words, higher GL ratings are not necessarily better for your transmission.

You should not use gear oils that contain friction modifiers in the transmission. Friction modifiers are designed to help reduce chatter and improve the performance of hypoid or clutch type limited slip differentials. They do not work well with synchronizers and can result in difficulties shifting.

Synchromesh is a special gear oil intented for use in certain GM and Chrysler transmissions. It was created by GM (ACDelco) and is licensed to Shell (Pennzoil and Quaker State) and Texaco. It is not API rated (GL) and has an approximate grade of SAE 80W so it is very thin and will likely cause extended wear. I would only suggest using this if you are willing to trade some protection for better shiftability.

Some people claim synthetic gear oils are too slippery for synchronizers but that is not true. Synthetic gear oils are superior to conventional gear oils as long as they are balanced with the right coefficient of friction which any quality oil should be.

I did this research because a lot of guys were having problems a short time after switching oils with the Mitsubishi transmissions. What I came to conclude is that it is best to either stick with the OEM oil or to order exotic and expensive synthetic transmission oils that meet your GL and viscosity ratings. I'm pretty sure there aren't any which meet these requirements that are sold in the US. Mobil 1 told me that the Mobilube 1 SHC (synthetic transmission oil) was their most advanced oil on the market (in Europe). If it was that hard for the largest company in the world to make a superior aftermarket transmission oil for GL-4 and GL-5 transmissions, then that should give you some idea of how specific they need to be to prevent corrosion, give you sufficient protection, and maintain smooth shifting. You almost always trade something off by going with a different transmission oil.

[brianc]

I know S2000 and RSX guys use Amsoil or GM Synchromesh to solve their notchyness in shifting or even grinding and gear pops.

[lordtakuban]

I have not tried the Motul gear oil yet (even though I sell the stuff). I do use 300V motor oil in the MR-S and that is certainly a step above the others there. I do know that Switching from Redline MT-90 to Amsoil 75x90 was a huge improvement. I haven't been that imporessed with the Redline MT-90. Others swear by it.

I most likely won't be changing the tranny fluid until around the first interval. And then, unless there is some big reason not to, I plan on using Amsoil.

Here's one downside to Amsoil, their whole dealer network is one big pyramid MLM nonsense. And good luck finding some on a store shelf. Retailers get no discount for having the product on hand. The best place to get it is likely amazon.com or ebay. You should be able to find the Motul stuff and Redline at a lot of places though.

[NeedsmoreCowbell]

Engine oil ----check

Transmission oil ---- check

Now all we have left is the diff and brake fluid left to solve

[Koji_Online]

Originally Posted by brianc

I know S2000 and RSX guys use Amsoil or GM Synchromesh to solve their notchyness in shifting or even grinding and gear pops.

+1 again; & not just GM SM, but with Friction Modified =D

So many technical threads is great info; I'm glad to have read all of everyone's research; though yes, for S2k & my RSX-S I had no trouble with 100k miles on GM... SM... FM haha (& I'm positive my RSX-S had brass synchros 1st-3rd) That car was notorious for actual grinds & extreme harshness, not just slight hesitations that people experience or are worried about in our new cars =P

[rice_classic]

Originally Posted by Bristecom

You should not use gear oils that contain friction modifiers in the transmission. Friction modifiers are designed to help reduce chatter and improve the performance of hypoid or clutch type limited slip differentials. They do not work well with synchronizers and can result in difficulties shifting.

I think this is the single most important thing said in this thread. :happy0180:The reason why people go on and on about GM Synchromesh with Friction Modifiers is because they are using it in FWD transmissions where the clutch/plate LSD is sitting in the same fluid the gearset is and the clutch's need a modifier. On FWD boxes with torsen diffs the friction modifiers are unnecessary. The same goes for the S2k box and the BRZ box.

Originally Posted by Bristecom

Synchromesh is a special gear oil intented for use in certain GM and Chrysler transmissions. It was created by GM (ACDelco) and is licensed to Shell (Pennzoil and Quaker State) and Texaco. It is not API rated (GL) and has an approximate grade of SAE 80W so it is very thin and will likely cause extended wear. I would only suggest using this if you are willing to trade some protection for better shiftability.

Remember that not all trannies are created equal. The Honda boxes obviously use Honda MTF which is thin (a 75w gear oil is equivalent to a 30w motor oil). If Honda recommended their own fluid (30w motor oil viscosity equivalent) for the S2000 transmission which is similar to that of the BRZ, why would it cause rapid wear? Some transmissions are designed for a thicker oil while others would see a decrease in protection and longevity by using a thicker oil. Also keep in mind that the gear and housing design of the transmission are designed to "pump" the oil through journals and help lubricate bearings. The oil's ability to "flow" is important also since most driving takes place where our transmission oil is below 200degrees F.

Originally Posted by Bristecom

Some people claim synthetic gear oils are too slippery for synchronizers but that is not true. Synthetic gear oils are superior to conventional gear oils as long as they are balanced with the right coefficient of friction which any quality oil should be.

This is not true in all cases and your qualifier regarding "right coefficient of friction" is case in point. It is true with Honda D-Series boxes, something I have lots of time with and this is well documented through the racing community who competes with D-Series engines/transmissions. The best oil for these boxes is the Honda MTF but if you're racing: Pennzoil stuff or 10w-30 dino oil. The "right coeffecient of friction" doesn't exist with 100% synthetic transmission fluids in a D-Box. The synchro simply doesn't slow the gear fast enough. In fact, in the 1980's the factory Honda manual recommended 10w-30 (non-synthetic) motor oil for the transmission. This wasn't changed until a few years later when Honda had developed their MTF.

Originally Posted by Bristecom

If it was that hard for the largest company in the world to make a superior aftermarket transmission oil for GL-4 and GL-5 transmissions, then that should give you some idea of how specific they need to be to prevent corrosion, give you sufficient protection, and maintain smooth shifting.

So long story short... It's hard to go wrong with OEM.

[Bristecom]

Originally Posted by rice_classic

Remember that not all trannies are created equal. The Honda boxes obviously use Honda MTF which is thin (a 75w gear oil is equivalent to a 30w motor oil). If Honda recommended their own fluid (30w motor oil viscosity equivalent) for the S2000 transmission which is similar to that of the BRZ, why would it cause rapid wear? Some transmissions are designed for a thicker oil while others would see a decrease in protection and longevity by using a thicker oil. Also keep in mind that the gear and housing design of the transmission are designed to "pump" the oil through journals and help lubricate bearings. The oil's ability to "flow" is important also since most driving takes place where our transmission oil is below 200degrees F.

Yes, every transmission is different. It sounds like the Honda gearboxes can get by with thinner oil and may not have as much potential for corrosion. Most transmissions I've seen though are 75W-90 or higher. So under hard use, the Pennzoil Synchromesh wouldn't hold up in those as well even though it has a neat way of stretching itself thin.

This is not true in all cases and your qualifier regarding "right coefficient of friction" is case in point. It is true with Honda D-Series boxes, something I have lots of time with and this is well documented through the racing community who competes with D-Series engines/transmissions. The best oil for these boxes is the Honda MTF but if you're racing: Pennzoil stuff or 10w-30 dino oil. The "right coeffecient of friction" doesn't exist with 100% synthetic transmission fluids in a D-Box. The synchro simply doesn't slow the gear fast enough. In fact, in the 1980's the factory Honda manual recommended 10w-30 (non-synthetic) motor oil for the transmission. This wasn't changed until a few years later when Honda had developed their MTF.

Well, here's the thing. Where were you guys able to find synthetic transmission oils that were actually designed to meet that transmission's requirements? In my research for the Mitsubishi transmissions, there were only 2 in the world at the time - one made by Pennzoil and one made by Mobil 1 in Europe. So it is likely that the problems you had with the synchros were due to something else, like it being the wrong GL rating or viscosity; not simply because it was synthetic. But even still, it is possible for them to get it wrong. As I said, it was even a challenge for Mobil 1 to get everything right. So perhaps it is harder for them to properly balance a synthetic gear oil for the synchros. But again, if the engineers of the oil actually had specific requirements in mind, it shouldn't end up too slippery or whatever.

So long story short... It's hard to go wrong with OEM.

Yeah, I'm all for improving things over OEM but this is the one fluid that I would use extreme consideration replacing. Sure, it may feel better at first but what about when your synchros start to wear or corrode 30,000 miles down the road? Or you go to change your oil again and find tons of metal shavings in it? Or you end up having to replace your transmission after 60,000 miles and then start claiming Toyota/Aisin has made a bad transmission.

So saying things like "Motul/RoyalPurple/Amsoil FTW!" may sound nice but at least show us an exact product that you believe will actually be an improvement. Since the OEM oil is GL-3, I highly doubt there is any out there that will convince me it's better than stock.

[Draco-REX]

Originally Posted by NeedsmoreCowbell

Engine oil ----check

Transmission oil ---- check

Now all we have left is the diff and brake fluid left to solve

Diff oil can be the same as the transmission oil. Our cars have torsen diffs, not clutchpack diffs. So friction modifiers are not needed.

Brake fluid is easy too. ATE Super Blue!

But really, unless you're going to track the car, regular DOT 4 is fine for 99.9% of the owners out there. Just keep it fresh by flushing it out every year or so.