Change your manual transmission fluid ASAP!!!

[itsAlex]

Originally Posted by Mr.ac

Reason: tranny and diff do not have dip sticks to measure. Only a "fill to the bottom of the filler hole" is what the service manual says. So if your car is on an incline or decline you might over/under fill. Which causes damage and such.

Even if you put in exactly 2.3l the tranny might have more fluid that didn't drain and you over fill or vice versa.

Thanks for the explanation, I never thought about there being remaining oil prior to filling, it makes sense now.

[FRSek]

Planning to swap to redline 75-90 or mtl at some point. I cant complain about the oem stuff, gears feel good to me, but ive been driving a 03 wrx with worn synchros the last few years. Great off topic info in thread on 2-->1 downshifts. It took me a while to find the right pt 5-6mph w rev match, as i like to creep up to lights where space allows.


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[RichardsFRS]

I've never had a car where I changed the fluid after a couple thou miles. I have 47,7 on my FRS, next time in for oil change it will get a tranny and diff change as well. I don't have any clunk except for the second first thing in the morn. I just shift smooth, and a few minutes it will shift fine with no clunk.

[Jonde875]

What everyone else says about Redline MT90 oil to transmission?

I think I will put it next time.

[roddy]

Originally Posted by Jonde875

What everyone else says about Redline MT90 oil to transmission?

I think I will put it next time.

MT-90 meets the spec and is a good fluid. However, if you are looking to change fluids just to improve shift quality, this won't be the answer. I tried it. If you are happy with the way it works now, and just want to replace the fluid, MT-90 is good. If you are looking to improve shift feel, and live in a cooler climate, try the MT-85 or Pentosin MTF2.

[XanRules]

So MT85 is the thread consensus for the Trans? What about for the Diff?

I am admittedly just not willing to look through all 20something pages of the thread right now hahaha

[GT86FI]

Originally Posted by XanRules

So MT85 is the thread consensus for the Trans? What about for the Diff?

I am admittedly just not willing to look through all 20something pages of the thread right now hahaha

Answer: Motul Gear 300 for both trans and diff

[Antihero983]

^This. Finally changed mine at 20k, and holy hell was it dark and ugly.

[Resolute]

I'm surprised so many like the Gear 300 in their transmission. GL-5 gear oils don't typically provide better synchro performance in transmissions.

I'll probably check out the Pentosin MTF 2 when it's time to change mine out, but I enjoyed Redline MT85 in my Z. If the MTF 2 proves too thin for hot track days, then I'll try the Redline in this transmission also.

[TrevorsTII]

Originally Posted by Resolute

I'm surprised so many like the Gear 300 in their transmission. GL-5 gear oils don't typically provide better synchro performance in transmissions.

I'll probably check out the Pentosin MTF 2 when it's time to change mine out, but I enjoyed Redline MT85 in my Z. If the MTF 2 proves too thin for hot track days, then I'll try the Redline in this transmission also.

Gear 300 is a GL-4 and GL-5 compliant liquid. GL-4 is used in transmissions because of yellow (brass) sincros. Where as GL-5 is for the differential. So since Gear 300 is safe with yellow metals it is perfectly fine for both transmission and differential.

[Resolute]

Originally Posted by TrevorsTII

Gear 300 is a GL-4 and GL-5 compliant liquid. GL-4 is used in transmissions because of yellow (brass) sincros. Where as GL-5 is for the differential. So since Gear 300 is safe with yellow metals it is perfectly fine for both transmission and differential.

Yes, Gear 300 is both GL-4 and GL-5, but a lubricant meeting both the GL-4 and GL-5 specifications is not necessarily suitable (much less better) for use in a transmission requiring GL-3 or GL-4 gear oil.

The GL-5 specification was created to establish a gear oil whose chemistry is better suited to handling the severe sliding and loading conditions imposed by hypoid gear mechanisms than GL-4 lubricants. To do so, GL-5 gear oils must have higher concentrations of extreme pressure (EP) and anti-wear additives than GL-4 oils. So, by design, a GL-5 gear oil can also be labeled as meeting the GL-4 requirement with the amount of EP additives it contains, in much the same way that a 93 octane fuel will 'meet' the lower anti-knock specifications of a 91 octane rated fuel. But they are not backwards compatible. In other words, while a GL-5 oil exceeds the GL-4 EP requirements, a GL-4 oil does not have enough EP additives or anti-wear characteristics to satisfy the GL-5 specification.

The extreme pressure (EP) additives used to meet the GL-5 oil standard must chemically alter (corrode) the gear surfaces in order to establish a film strong enough to withstand the high pressures of the gear loads and also not be removed by heat and friction. Most EP additives are composed of sulfur, phosphorous and chlorine compounds because of their ability to bond with and chemically alter steel surfaces. When these compounds corrode the surface of softer metals such as brass or copper, they can be removed from the softer native metal by friction. This leaves softer metals looking pitted. Hence, the old scare that GL-5 gear oils will destroy brass synchros in a transmission. This is really not a huge issue for most gear oils though, GL-5 or otherwise, since modern gear oils typically contain buffer compounds that prevent EP additives from bonding with and corroding the surfaces of softer metals. If it's spec'd for manual gearboxes, GL-5 or otherwise, you shouldn't have an issue with pitting soft metals.

The real problem with GL-5 oils in a transmission is that the EP additives also reduce the sliding friction across the reacted surfaces. This is normally a good thing, but the synchronizers in a manual transmission require friction to operate. When you use your shift lever to slide a synchronizer ring (spinning at the same speed as your input shaft) into a selected drive gear (spinning at a different speed), friction is what transfers the energy from the synchronizer to the selected gear and brings it up (or down) to speed. Once the rotating speed of the gear matches the synchronizer, then the locking ring on the synchro can slide over and lock into the drive gear, completing the shift. How long this process takes is directly impacted by the rate of frictional energy transfer. Oils which meet the GL-5 specification will slow this energy transfer down because they reduce friction across the reacted gear surfaces.

Manual transmissions that spec a GL-4 oil (or even a GL-3 oil for our cars), are specifying a gear oil with lower amounts of EP and anti-wear characteristics in order to improve synchronizer operation. This is a pretty common practice for manufacturers whose manual transmissions do not contain hypoid gears Manual transaxles tend to specify a GL-5 because gear protection trumps shift feel in that application.

I have typically found GL-5 gear oils in manual transmissions to have worse synchro performance than GL-3 or GL-4 oils, hence my surprise that so many here seem to prefer it. I wonder how much of that preference really comes down to advertising and having the Motul name on the bottle.

[Amillionoh7]

Switched mine to Royal purple maxgear 75w90 at 14k and have had no problems.

[YamahaR86]

I've upgraded my bushings and mtec springs. Planning on changing out my oils at the 30k mark which is in another 4-5k.

[Toyarzee]

Interested to seeing responses to the detailed and legitimate description and concerns provided above by @Resolute.