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Synthetic lube bad for paper lining in synchros?

Posted by wparks, Sep 13, 2013

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  1. wparks

    wparks Proven Member

    Joined Mar 19, 2012
    Fort Collins, Colorado
    Ok- here's a weird one-

    Just had my 1G AWD manual transmission rebuilt by a very reputable local shop (Advanced Transmission and Clutch in Fort Collins, CO). They deal with many older and racing transmissions and have a stellar reputation.

    I was asking the main guy about transmission oils, and all of the disagreements on the forums about amsoil vs redline, vs BGsynchroshift, etc etc. He said "look- the syncros in this car actually use paper material (he said lining), so stay away from anything synthetic as it will destroy them." He agreed that I should stay away from GL5 because it's corrosive to the yellow metal in the synchros. He said just use regular GL4, non synthetic, and you'll be fine.

    Has anyone heard this? I thought synthetic (my favorite is Amsoil) was totally the way to go, and I have never heard of paper anything in synchros. You?
  2. T is for TURBO

    T is for TURBO Proven Member

    Joined Jan 15, 2005
    Milwaukee, Wisconsin
    Early 1g transmissions used organic lined syncos, and yes, they don't mix well with certain oils. Later mitsu went to brass syncros, which are not sensitive to types of oil. I believe you can upgrade to the brass syncros, but I'm not 100% sure about that.

    I run MT-90 and I have zero complaints so far, shifts smooth as butter at 7.5k

    Street Build 981  0

    1996 Eagle Talon TSi
    manual · 2G DSM
  3. TSIfreek

    TSIfreek Proven Member

    Joined Dec 14, 2003
    cary, Illinois
    Our syncos are all brass now

    1K  0

    1990 Eagle Talon TSi AWD
    11.27 @ 127 · 1G DSM
  4. synthetek

    synthetek DSM Wiseman

    Joined Dec 13, 2005
    La palma, California
    I have only heard of this being an issue with the NVT-350 trans in the 2g NT

    3K  0

    1999 Mitsubishi Eclipse GSX
    13.629 @ 99.970 · 2G DSM

    Street Build 2K  0

    1995 Mitsubishi Eclipse GSX
    manual · 2G DSM
  5. Dude McGee

    Dude McGee Proven Member

    Joined Aug 4, 2013
    Joliet, Illinois
    If it helps, I always use MT-90. In my personal car I run a stock 92 awd trans, and it has been fine (knock on wood). Ive also never heard of this, though, and I find it interesting.

    Does it have a warranty? If so, Id use what they recommend to keep that warranty intact.

    434  0

    1993 Eagle Talon TSi AWD
    · 1G DSM
  6. jrohner

    jrohner Proven Member

    Joined Sep 25, 2004
    Willmar, Minnesota
    So you had your tranny rebuilt, and they used the old style 90 syncros? Weird.

    2K  0

    1991 Mitsubishi Eclipse GSX
    11.415 @ 119.59 · 1G DSM

    4K  0

    1998 Mitsubishi Eclipse GSX
    414 whp · 459 lb/ft · 2G DSM
  7. ricktb

    ricktb Proven Member

    Joined May 20, 2007
    Edmonton, AB, Canada
    Yeah I heard of this for the 2g 420A FWD transmission... At first, I used a heavy generic 75W 90 GL-5 gear oil for a while and the shifting got rougher and rougher, so I swapped it out for a super thin ATF+4, yea thats automatic trans fluid and it worked really nice, smoothed out the shifts and supposedly good for the paper lined synchos. I think for the 4g63 transmissions you'd want to use anything GL-4, not sure about paper lined synchos in these ones.

    520  0

    1995 Eagle Talon TSi AWD
    manual · 2G DSM
  8. RSTurboFWD90

    RSTurboFWD90 Proven Member

    Joined May 9, 2006
    Atlanta, Georgia
    I replaced the factory gearbox lube with BG SyncroShift II in 2002. I have not had any issues. This is however a very low mileage car. I've only put on 12k miles since then. This is a 1990 FWD car.
  9. goodhart

    goodhart Proven Member

    Joined Sep 22, 2006
    Isanti, Minnesota
    Use what the shop tells you to use. If not, you're basically throwing any warranty out the window.
  10. ErikTande

    ErikTande Supporting Member

    Joined Dec 17, 2012
    Centennial, Colorado

    Street Build 838  1

    1997 Eagle Talon TSi AWD
    awd · manual · 2G DSM

    3K  7

    1990 Mitsubishi Eclipse GSX
    13.2 @ 105 · 1G DSM
  11. wparks

    wparks Proven Member

    Joined Mar 19, 2012
    Fort Collins, Colorado
    That's a great link ErikTande! I love this part:

    Transmission, ALL Mitsubishi:
    DO NOT use Synchromesh, BG Synchroshift I or II, or Royal Purple. These fluids will destroy synchros and gears and void your warranty!

    I have no idea where to get that specialized Mitsubishi factory oil- sounds like MT90 is where it's at.
  12. DSM1G90

    DSM1G90 Proven Member

    Joined Apr 6, 2008
    Nampa, Idaho
    Yea .. the NEON transmissions uses the ATF+4 fluid since it needs the friction modifier for them "paper lined" syncros.

    1K  0

    1990 Plymouth Laser RS Turbo
    · 1G DSM
  13. goodhart

    goodhart Proven Member

    Joined Sep 22, 2006
    Isanti, Minnesota
    :confused: I guess the dealership might be a good spot to start? :confused:
  14. bastarddsm

    bastarddsm Proven Member

    Joined Aug 26, 2003
    Mendota, Illinois
    I don't know the a brass synchro is an upgrade. It certainly lasts better, but a new fiber synchro shifts better. I run old used fiber ones with gl5, and shift at 9500 with a 2600, and have good results.

    Always run a heavy gear oil in these transmissions.

    Showcar Build 5K  1

    1991 Eagle Talon N/T
    9.805 @ 144.00 · 1G DSM
  15. wparks

    wparks Proven Member

    Joined Mar 19, 2012
    Fort Collins, Colorado
    Yes, Yes, I know Goodhart the dealer has it. What I was thinking when I wrote that is that I won't set foot in a dealership unless my life depended upon it. They don't even use Vaseline there!

    This shop specializes in older transmissions, and the rebuild was an OEM style rebuild, so I don't mind that he used the original type of synchros. The last ones lasted 185K of hard high-school driving, and I'm not a street racer, so I'm happy. It's still wearing in so it's not as smooth yet as I like, but a few thousand miles of gentle care and some MT-90 and I think it will be as sweet as YooHoo. Next time I'll probably go to Jacks- Thanks for the recommend ErikTande.

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