ehsnils Posted September 16, 2017 Share Posted September 16, 2017 Worn 1st and 2nd gear synchros are not unique to Subies, and is just something that happens over time. They need a certain amount of friction to work. Changing oil mix lowers the the oil film thickness and increases friction but that also applies to other parts in the gearbox like gear surfaces. So I'd be careful with changing oil mix. But changing oil in the gearbox now and then is not a bad idea to ensure that old sludge and metal particles are evacuated. Also read this: Just remember that API GL-4 and GL-5 are gear oil ratings, not transmission oil ratings. Transmissions have gears and synchronizers which seemingly conflicting requirements must be met differently. A normal GL-4 gear oil with any given viscosity has about 1/2 level of sulfur/phosphorous additive that would be in the GL-5 product, so the bond is not as strong, and therefore can be peeled off without peeling a layer of brass (or less brass). This means that the GL-4 product provides a little less extreme pressure protection, so in the differential of a high powered car, it would not be the ideal product in the differential. To understand this need we should be aware of the fact that the differential is where the final torque is applied to the wheels. When we use a GL-5 product in a transmission that requires GL-4, we normally find 2 to 4 times as much copper in the used oil as we would with a GL-4 product Eventually the synchronizers wear to the point that they no longer make contact with the other half of the cone, bottoming out before stopping the opposing gear. https://www.linkedin.com/pulse/difference-between-gl-4-gl-5-gear-oils-manual-transmission-daniel-shi Link to comment Share on other sites More sharing options...
ToRealEyes Posted September 19, 2017 Share Posted September 19, 2017 Is Subaru's own High Performance Gear Oil aka 'HPGO' problematic in these transmissions? It's accessible, relatively cheap, and even worst case scenario, we LGT members are excessive with maintenance, and likely changing transmission oil every 50k or less. Given these factors, would it cause harm to use this over the old standby Extra-S? We just replaced our trans and rear diff oils for our 2012 6MT with HPGO about 10k miles ago. Silky smooth as far as I can tell. If the 6MT is really just an evolution of the older 5MT in the WRX, then I'm going to change out our old WRX's gear oils with HPGO next chance I get. Link to comment Share on other sites More sharing options...
dgoodhue Posted September 19, 2017 Author Share Posted September 19, 2017 Is Subaru's own High Performance Gear Oil aka 'HPGO' problematic in these transmissions? It's accessible, relatively cheap, and even worst case scenario, we LGT members are excessive with maintenance, and likely changing transmission oil every 50k or less. Given these factors, would it cause harm to use this over the old standby Extra-S? We just replaced our trans and rear diff oils for our 2012 6MT with HPGO about 10k miles ago. Silky smooth as far as I can tell. If the 6MT is really just an evolution of the older 5MT in the WRX, then I'm going to change out our old WRX's gear oils with HPGO next chance I get. The HPGO is 75w90 that meets the lubrication requirements. Here is a thread on NASOIC with an samples. https://forums.nasioc.com/forums/showthread.php?t=2678891 Link to comment Share on other sites More sharing options...
ehsnils Posted September 19, 2017 Share Posted September 19, 2017 See the synchronization issue as a great way to learn how to perform double clutching: [ame=http://www.youtube.com/watch?v=tescWzTlGQ0]What Is Double Clutching? - YouTube[/ame] Link to comment Share on other sites More sharing options...
smash209 Posted September 21, 2017 Share Posted September 21, 2017 Is Subaru's own High Performance Gear Oil aka 'HPGO' problematic in these transmissions? It's accessible, relatively cheap, and even worst case scenario, we LGT members are excessive with maintenance, and likely changing transmission oil every 50k or less. Given these factors, would it cause harm to use this over the old standby Extra-S? We just replaced our trans and rear diff oils for our 2012 6MT with HPGO about 10k miles ago. Silky smooth as far as I can tell. If the 6MT is really just an evolution of the older 5MT in the WRX, then I'm going to change out our old WRX's gear oils with HPGO next chance I get. You are in the lucky club where the full GL-5 works great. Maybe you have low miles or really low syncro wear. Sweet! From what I have gleaned every trans is different so use what works for you and hopefully what works is also protecting your trans and front diff enough! I have had good luck with Motul (also GL5) but didn't get a decent shifting feel until I replaced a qt with lightweight shockproof (technically not GL rated). I feel ok about the tradeoff. Link to comment Share on other sites More sharing options...
dgoodhue Posted December 27, 2017 Author Share Posted December 27, 2017 I had done a quick review on the ExtraMT in my GT 6MT that apparently forgot to link to this thread. http://legacygt.com/forums/showpost.php?p=5697930&postcount=2366 It was 5 degrees out this morning and my transmission wasn't difficult to get in any gear. On a cold day like today with the Motul300 in my 2.5i, I use to drive the length of my street (couple hundred yards) in 1st gear. (The factory fill was even more ridiculous.) It is even more impressive since I have STS and STS shift adapter for a very short shift throw length which gives me less leverage. My 2.5i just had the STS shifter with the Motul300. The transmission still does not grind going into reverse like it did with Uncle Scotties cocktail. After 8000 miles I am very happy with the ExtraMT, the only hurdle is the next oil sample report I will have that done in 17k miles (25k oil change to align it with the 120k, 150, maintenance intervals) Link to comment Share on other sites More sharing options...
bluesuby Posted December 27, 2017 Share Posted December 27, 2017 See the synchronization issue as a great way to learn how to perform double clutching: One item not mentioned is that double clutching on downshifts on a wet or snowy road helps maintain stability without "jerking" the drivetrain. Link to comment Share on other sites More sharing options...
bluesuby Posted December 27, 2017 Share Posted December 27, 2017 No mention of Redline 75-90 NS? It's very synchro friendly and I was happy with it for a number of years. I bought a case of Subaru High Performance Gear Oil and after 3 changes and my final refill I noticed the funnel screen was getting clogged and little red pebbles had formed, presumably they had precipitated and fallen out of the oil mix. I'm going back to Redline next Spring. Link to comment Share on other sites More sharing options...
cww516 Posted December 27, 2017 Share Posted December 27, 2017 I've got this bookmarked: http://legacygt.com/forums/showpost.php?p=5537348&postcount=453 I seem to recall that he's moved away from the 75-90 NS, although I can't remember why at the moment. Link to comment Share on other sites More sharing options...
skierd Posted December 28, 2017 Share Posted December 28, 2017 I’ve got a 2.5i 6mt (outback). I bought it used with 29k on it and I assume the fluid in it was stock original when I bought it two years ago. I changed it at 80k miles this fall with Carquest synthetic 75w90 and it’s been great so far. A little stiff at -20F but nowhere near as bad as what was in the car last winter, goes in to reverse without grinding from cold, it shifts fine to 2nd by the end of my 1/8 mile driveway. YMMV... Link to comment Share on other sites More sharing options...
dgoodhue Posted February 19, 2018 Author Share Posted February 19, 2018 I was ordering part for my timing belt and was using the OEM Subaru parts website for parts. I was looking for OEM Coolant and found a fluids section. 75w80 Extra MT shows up as the transmission fluid for my '12 GT. Link to comment Share on other sites More sharing options...
brandon.mol Posted February 19, 2018 Share Posted February 19, 2018 I've run 100% Redline Lightweight shockproof in mine for years and its fantastic in any temperature from -40C to + 40C with no problem putting it in 1st or 2nd gear from a roll. The LWSP allows for better hydraulic pressure on the synchros than a typical GL-4 75w90 gear oil. And yet it has the shock loading capabilities of a 140 weight. Best of both worlds. I wouldn't run anything else. Link to comment Share on other sites More sharing options...
dgoodhue Posted February 19, 2018 Author Share Posted February 19, 2018 I've run 100% Redline Lightweight shockproof in mine for years and its fantastic in any temperature from -40C to + 40C with no problem putting it in 1st or 2nd gear from a roll. The LWSP allows for better hydraulic pressure on the synchros than a typical GL-4 75w90 gear oil. And yet it has the shock loading capabilities of a 140 weight. Best of both worlds. I wouldn't run anything else. I used the LWSP oil in my rear differential of my Syclone. I didn't like the way it looked, honestly it kind of freak me out and I didn't use it again. I use Redline 10w30 motor oil, Racing ATF, and 75w90NS gear oil in Syclone. I done oil samples on the motor oil and ATF, so obviously I am a fan of Redline products. The LWSP doesn't have viscosity rating. As with most Redline oils, it don't have a manufacturers approval rating. Obviously it doesn't stop me from using redline oil, but it would have me think twice about using it warrantied vehicle. From what I have read Redline recommends 75w90NS for the 5 speed Subaru transmission. It is not something I am willing to blindly try. I need more evidence than that if I am going to risk a $6500 transmission on it. I am guessing you didn't do an oil sample analysis on it. Link to comment Share on other sites More sharing options...
brandon.mol Posted February 20, 2018 Share Posted February 20, 2018 I'm sorry to hear that you decide what a good gear oil is based on it being blue. Go ahead and don't use it. I literally do not care one bit. I am just presenting my experience which has been excellent, and is in line with the product claims. Link to comment Share on other sites More sharing options...
dgoodhue Posted February 20, 2018 Author Share Posted February 20, 2018 I looked at my redline oil inventory and I used superlight weight shock proof gear oil, not the LWSP gear oil. It wasn't blue, it came out looking milky looking like when my outboard engine lower unit seal was allowing water in. The way the oil looked wasn't my only hesitation for using it. Link to comment Share on other sites More sharing options...
brandon.mol Posted February 20, 2018 Share Posted February 20, 2018 Well there is your problem. You used the wrong stuff. The superlight weight is not appropriate for use in place of a 75w90 over a long term. That's an oil made for qualifying laps, etc. Not suitable for daily driving. It's only as thick as a 10W/ATF. Link to comment Share on other sites More sharing options...
hichamaziz Posted February 20, 2018 Share Posted February 20, 2018 good read thanks for the info. Link to comment Share on other sites More sharing options...
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