Th3Franz Posted November 14, 2010 Share Posted November 14, 2010 you have a GT with rear LSD? i thought it is to be used only for top off? i figure it doesn't have the correct additives for LSD? The GT has a viscous rear LSD. Yours has an open diff. In both cases, the gear oil itself does not affect the lockup behavior of the differential. Clutch type diffs are picky about their oil. You can run any GL-5 75w90 gear oil. I ran Redline 75w90 in my rear diff with good results. A more slippery gear oil in the rear diff will reduce operating temps. -Franz The end of a Legacy http://www.youtube.com/th3franz Link to comment Share on other sites More sharing options...
mccorry Posted November 15, 2010 Share Posted November 15, 2010 No... the LGT has an OPEN front diff... a VISCOUS center diff... and a LIMITED SLIP rear diff. Link to comment Share on other sites More sharing options...
rtbrjason Posted November 15, 2010 Share Posted November 15, 2010 Is the Supertech Synthetic 75w90 advisable for use in the 6mt trans/diff as well as the R180 rear diff without any additives? Link to comment Share on other sites More sharing options...
Impulse Posted November 15, 2010 Share Posted November 15, 2010 No... the LGT has an OPEN front diff... a VISCOUS center diff... and a LIMITED SLIP rear diff. FYI: Viscous [coupling] is a type of limited slip differential. As are helical gear, clutch type, and electromagnetic. The STI has a gear type (Torsen) rear diff, ours is viscous coupling. Link to comment Share on other sites More sharing options...
naimouasta Posted November 15, 2010 Share Posted November 15, 2010 spec b has rear torsen to i believe. as for refilling the rear LSD with this supertech stuff, i now believe its fine, because the viscous diffs are sealed units correct? you only need the fluids with friction modifiers if its a clutch type diff. Link to comment Share on other sites More sharing options...
goneskiian Posted November 15, 2010 Share Posted November 15, 2010 as for refilling the rear LSD with this supertech stuff, i now believe its fine, because the viscous diffs are sealed units correct? you only need the fluids with friction modifiers if its a clutch type diff. That's correct. The viscous diff's are sealed. Link to comment Share on other sites More sharing options...
mccorry Posted November 15, 2010 Share Posted November 15, 2010 FYI: Viscous [coupling] is a type of limited slip differential. As are helical gear, clutch type, and electromagnetic. The STI has a gear type (Torsen) rear diff, ours is viscous coupling. Nope. LGT rear differentials are clutch type... not viscous. Link to comment Share on other sites More sharing options...
Th3Franz Posted November 16, 2010 Share Posted November 16, 2010 (edited) we don't have a clutch type rear diff. where did you get that info from? from the service manual: Edited November 16, 2010 by Th3Franz -Franz The end of a Legacy http://www.youtube.com/th3franz Link to comment Share on other sites More sharing options...
mccorry Posted November 16, 2010 Share Posted November 16, 2010 (edited) Doh.... I stand corrected. Just checked my manual as well. Sorry for the wrong info. That's what I get for going off memory. Edited November 16, 2010 by mccorry Link to comment Share on other sites More sharing options...
Th3Franz Posted November 16, 2010 Share Posted November 16, 2010 No worries In the end, at least we have a diff that's not very picky at all about the fluid that's in it hehe -Franz The end of a Legacy http://www.youtube.com/th3franz Link to comment Share on other sites More sharing options...
maniaxzero Posted May 15, 2012 Share Posted May 15, 2012 damn this supertech 75w90 fluid was hard to find in local walmarts. Had to hit up a few different walmarts to collect my 5 quarts. It's been a few years since this thread been started. Anybody run into any problems with this gear oil? Link to comment Share on other sites More sharing options...
slowGT Posted June 1, 2012 Share Posted June 1, 2012 Glad this thread was bumped. Put some in and shifting has been great. I've used uncle scotty cocktail, redline, subaru extra S, castrol, and this fluid is by far the best so far. Time will tell though. Link to comment Share on other sites More sharing options...
maniaxzero Posted June 2, 2012 Share Posted June 2, 2012 Glad this thread was bumped. Put some in and shifting has been great. I've used uncle scotty cocktail, redline, subaru extra S, castrol, and this fluid is by far the best so far. Time will tell though. so you feel supertech is better than extra S? Link to comment Share on other sites More sharing options...
slowGT Posted June 2, 2012 Share Posted June 2, 2012 Well yes and I dunno.. It is shifting much, much better than any other fluid I have tried. I am maybe a little too picky, but the supertech stuff shifts by far the best. As far as if it is "better" than the Extra S I don't have any lab analysis of either stuff as a virgin sample. I also don't have any uoa of both fluids of similar mileage and driving conditions. So without this I can't really say that it is "better". I have only put a few hundred miles on the stuff so far but again I have tried just about every gear oil out there. Suprisingly this stuff has been the best. I am really happy with it. Link to comment Share on other sites More sharing options...
rgeo13 Posted March 27, 2018 Share Posted March 27, 2018 Going to bump this up. Used this in my '11 Legacy 6mt in gear box and rear diff. Already a considerable amount of improvement. Now, car has just a hair under 116k, last recorded time the gearbox oil was done was at 54k, rear diff I don't think has ever been done. So I really can't say how great it is, other than my shifts are now literally buttery smooth. I will update if I have any problems within the next 30k miles! Link to comment Share on other sites More sharing options...
Dishwasher Posted March 29, 2018 Share Posted March 29, 2018 I use Valvoline 75w90 gl5, and it's fine. Brought to you by Pfizer Link to comment Share on other sites More sharing options...
gutzjustin24 Posted August 10, 2018 Share Posted August 10, 2018 Just bringing some life to an old thread! I've been running Supertech SynBlend 75w-90 up front and Full Synthetic 75w-90 in the rear diff. Great stuff at a steal of a price. I know it's probably overkill but at less than 20 for 4 quarts I simply replace it every summer. Link to comment Share on other sites More sharing options...
Homedepotmade Posted May 3, 2019 Share Posted May 3, 2019 I am running Subaru's 75W90 High Performance Gear Oil and it sucks after 6 months of driving. I am seriously going trying this out. Link to comment Share on other sites More sharing options...
rgeo13 Posted May 8, 2019 Share Posted May 8, 2019 I am running Subaru's 75W90 High Performance Gear Oil and it sucks after 6 months of driving. I am seriously going trying this out. I'm over 1 year and 11,000 miles in on it, still feels just as buttery as it did on day 1. Even on brutal cold days we had this past winter. Try it!! If you aren't satisfied, drain and replace, and at the very least you did a solid flush for like $30. Link to comment Share on other sites More sharing options...
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