I own a 1992 Mitsubishi 3000GT VR4. It has a 5 speed Getrag transmission. The synchros are brass, and the recommended gear oil rating is GL4. I am currently using BG Synchroshift II. There is a "myth" going around that using a GL5 fluid may be hazzardous to the synchros and transmission internals. Can this be true?
GL4 and GL5 fluid..is this a myth?
- Thread starter SkortchGT
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As I understand it.......Some GL-5 fluids are corrosive to soft metals, such as brass.
Hmm, interesting. Guess I should stick with GL4 fluids. If this is true, I am curious as to why there are fluids recommended both GL4 and GL5?
MolaKule
Staff member
Search the Interesting Article section:
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=4;t=000226
http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=4;t=000226
Can anyone confirm whether Synchromesh is yellow-metal safe? I've heard that it is.
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GL-4 or, to a greater extent GL-5, lubricants can, if not properly formulated, become corrosive to yellow metals if the lubricant temperature exceeds 250 degrees F.
The API recently came out with a new specification to address this possibility. It's called MT-1. Lubes which meet MT-1, will not attack yellow metal even if the temperature does climb to this extremely high 250 degree mark.
"Mobil 1 Synthetic Gear Lubricant LS 75W-90 meets the most severe API Service MT-1 and GL-5 EP gear oil service classification"(www.mobil1.com)
It's very unlikely your gear oil will reach 250 degree F in a street car. Just touch the transfer case after a long drive.
The API recently came out with a new specification to address this possibility. It's called MT-1. Lubes which meet MT-1, will not attack yellow metal even if the temperature does climb to this extremely high 250 degree mark.
"Mobil 1 Synthetic Gear Lubricant LS 75W-90 meets the most severe API Service MT-1 and GL-5 EP gear oil service classification"(www.mobil1.com)
It's very unlikely your gear oil will reach 250 degree F in a street car. Just touch the transfer case after a long drive.
MolaKule
Staff member
GM Synchromesh and Pennzoil Synchromesh are safe for brass synchronizers and sintered-metal synchronizers.
GM Synchromesh fluid is synthetic, whereas Penzoil Synchromesh is Group I paraffinic. Both are essentially 9-10 cSt fluids.
[ April 16, 2004, 05:30 PM: Message edited by: MolaKule ]
GM Synchromesh fluid is synthetic, whereas Penzoil Synchromesh is Group I paraffinic. Both are essentially 9-10 cSt fluids.
[ April 16, 2004, 05:30 PM: Message edited by: MolaKule ]
Here is a pretty interesting posting I found
http://www.turbodieselregister.com/forums/archive/topic/1237.html
Its titled "IS GL-4 OBSOLETE?"
http://www.turbodieselregister.com/forums/archive/topic/1237.html
Its titled "IS GL-4 OBSOLETE?"
MolaKule,
Is it safe to assume that Redline MTL is safe for brass synchronizers?
Dave, the Redline Tech guy does claim that even though they are not MT-1 certified they can pass the certification requirements... I hope he's right… He did claim that they did notice staining/flaking of brass at around 300F.
Is it safe to assume that Redline MTL is safe for brass synchronizers?
Dave, the Redline Tech guy does claim that even though they are not MT-1 certified they can pass the certification requirements... I hope he's right… He did claim that they did notice staining/flaking of brass at around 300F.
MolaKule
Staff member
wrangler,
Yes. You will get a minor amount of brass flaking no matter what oil you use.
That link refers to data that is somewhat obsolete itself.
EP additives today are encased in non-reactive sulfur-phosphorus packages that contain copper deactivators, rust inhibitors, and oxidation inhibitors, so they do not attack copper alloys or stain them. Spur gears in manual transmission oils don't need the full EP protection that do Hypoid differentials.
Yes. You will get a minor amount of brass flaking no matter what oil you use.
That link refers to data that is somewhat obsolete itself.
EP additives today are encased in non-reactive sulfur-phosphorus packages that contain copper deactivators, rust inhibitors, and oxidation inhibitors, so they do not attack copper alloys or stain them. Spur gears in manual transmission oils don't need the full EP protection that do Hypoid differentials.
I am a retired former tribologist. GL-5 gear oils, esp early in the adoption of the GL-5 spec, sometimes contained "active" sulphur compounds, which could react with yellow metals in transmissions to damage them. The jump from GL-4 to GL-5 was major in terms of load carrying ability, and sulphur compounds were found to be part of the answer. I would still follow the mfr's (vehicle) recommendations - if they say GL-4, use GL-4. Red Line has retained GL-4 rating for its MTL and MT-90 gear oils for this reason. If you are determined to use GL-5 in a transmission, ensure that the mfr is not using active sulphur compounds.
Frankly, i do not see the need, at least in most passenger cars, even high perf ones. The loads seen on the gears are not nearly as high as seen in the differential. Many modern transmissions (like the TTC T-56 used in Vettes, Vipers, and SVT Cobras, spec Dex III/Mercon V ATF) use light gear oils, ATF's, or products like GM Synchromesh or Honda MTF, which are essentially "fortified" engines oils with higher levels of ZDDP, and some sort of friction modifier (like Ca) to offset the lubricity of engine oil, and allow some "bite" on the synchros to ensure smooth action. On some of the T-56's, they have gone to carbon-fiber syncros, which based on my examionation of some early field units, can cause too much lubricity, causing glazing, which messes up the gear feel and can even cause crunching.
Frankly, i do not see the need, at least in most passenger cars, even high perf ones. The loads seen on the gears are not nearly as high as seen in the differential. Many modern transmissions (like the TTC T-56 used in Vettes, Vipers, and SVT Cobras, spec Dex III/Mercon V ATF) use light gear oils, ATF's, or products like GM Synchromesh or Honda MTF, which are essentially "fortified" engines oils with higher levels of ZDDP, and some sort of friction modifier (like Ca) to offset the lubricity of engine oil, and allow some "bite" on the synchros to ensure smooth action. On some of the T-56's, they have gone to carbon-fiber syncros, which based on my examionation of some early field units, can cause too much lubricity, causing glazing, which messes up the gear feel and can even cause crunching.
Aside from the compatability with yellow metals, the gear oil has to allow the synchronizers to work. this require two flat or conical surfaces to reach the same speed as quickly as possible without spinning and heating up.
I've seen many synchronizers that have burned blue because the additive package wouldn't let go and let the discs spin. This means that depending on the materials used, the angles of contact, depth of contact, and type of drain grooves, different oils can be necesary. I try to stay with the GL-4 product whenever the manufacturer calls for it so as to be sure that they synchronize.
I've seen many synchronizers that have burned blue because the additive package wouldn't let go and let the discs spin. This means that depending on the materials used, the angles of contact, depth of contact, and type of drain grooves, different oils can be necesary. I try to stay with the GL-4 product whenever the manufacturer calls for it so as to be sure that they synchronize.
widman, when is Chevron going to come out with a GL-4 synchromesh fluid?
--- Bror Jace
--- Bror Jace
Thanks for the like to that article. So if i were to use a GL-5 fluid, it would have to also be rated MT-1? I'll keep my eye out.
i hope this isn't a hijack, but how is GL-3 different from the other 2? there's a pretty big difference in opinion as to what the fluid requirements are for the ZF6 used in the C4 corvette, i've heard that it's GL-3. according to ZF, the only "approved" fluids are a GM fluid (which is not syncromesh), and castrol TWS 10w60 engine oil.
-michael
-michael
Product Description:
RTF is specifically engineered to reduce fluid drag for increased power efficiency without compromising component durability. It is made from a combination of specially selected 100% synthetic Group IV/V base oils proving superior shear resistance and extreme temperature stability. RTF is specially formulated to exceed the load-carrying and extreme pressure wear protection properties of higher viscosity GL-5 or GL-6 gear oils. RTF provides anti-score protection for high speed, high load and high torque shock-loading conditions, while allowing smooth operation of synchronizers. Features & Benefits:
Group IV/V 100% Synthetic Formula
Maximizes power throughput
Reduces gear box temperatures
Superior level of shock load, EP and wear protection
Typical Uses:
Recommended for manual transmissions, transaxles and marine outdrive units where an SAE 75W90, 80W90 or 90 is specified. Also replaces SAE motor oil 10W30, 30, 10W40 or 40 where specified for transmissions.
Commonly used in circle track (Winston Cup, Busch, modified, stock), road racing, formula, open wheel (Champ Cars, IRL Cars), off road, drag racing, sports compact street and domestic performance street applications.
Highly recommended for achieving maximum power efficiency. Excellent for dry sump and fluid drive gear cases. Note: RTF is specifically recommended for Richmond Gear Racing Transmissions
Torco
RTF is specifically engineered to reduce fluid drag for increased power efficiency without compromising component durability. It is made from a combination of specially selected 100% synthetic Group IV/V base oils proving superior shear resistance and extreme temperature stability. RTF is specially formulated to exceed the load-carrying and extreme pressure wear protection properties of higher viscosity GL-5 or GL-6 gear oils. RTF provides anti-score protection for high speed, high load and high torque shock-loading conditions, while allowing smooth operation of synchronizers. Features & Benefits:
Group IV/V 100% Synthetic Formula
Maximizes power throughput
Reduces gear box temperatures
Superior level of shock load, EP and wear protection
Typical Uses:
Recommended for manual transmissions, transaxles and marine outdrive units where an SAE 75W90, 80W90 or 90 is specified. Also replaces SAE motor oil 10W30, 30, 10W40 or 40 where specified for transmissions.
Commonly used in circle track (Winston Cup, Busch, modified, stock), road racing, formula, open wheel (Champ Cars, IRL Cars), off road, drag racing, sports compact street and domestic performance street applications.
Highly recommended for achieving maximum power efficiency. Excellent for dry sump and fluid drive gear cases. Note: RTF is specifically recommended for Richmond Gear Racing Transmissions
Torco
i agree. the synth synchromesh is the syntorq castrol stuff. the regular $9 synchromesh is either pennzoil or texaco.
-michael
MolaKule
Staff member
Yes I am.
The fluids I am referring to are the GM Manual Transmission Fluid in the Blue-Silver-Grey bottle and the Pennzoil Synchromesh in the bright Yellow bottle.
Guys, I'm 99% certain that GM is buying their fluids from a major refiner/blender ... and am almost as sure that the Pennzoil and Texaco/Chevron fluids are different as these folks are full service, competing petro-chemical conglomerates.
Synchromesh fluids are not really that hard to produce ... it's just that other fluids used to be "good enough" for the transmissions of the past so many are relatively new.
--- Bror Jace
Synchromesh fluids are not really that hard to produce ... it's just that other fluids used to be "good enough" for the transmissions of the past so many are relatively new.
--- Bror Jace
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