GL4 and GL5 fluid..is this a myth?

[harrydog]

So if a manufacturer (Subaru) specifies GL5 for my car's transmission, is it safe for me to use a synthetic GL4? Apparently the products that seem to work best (smoother shifting, eliminate synchro grinding) are GL4. For example Redline MT90 seems to work really well. But Redline 70w90ns gear oil, which is a GL5, does not seem to work as well for most people.
Also, lots of Subaru owners are swearing by Redline Lightweight Shockproof, but again, I don't think this is rated GL5.

 

[harrydog]

Anybody...?
Is it a bad idea to use a GL4 in a transmission where a GL5 is recommended?

 

[1sttruck]

A reply to another thread- Check the products for Dodge Diesels at Standard Transmission, where a gallon is $54. The Dodge dealers get a hefty premium for their bottled oil. From another site:

Here is the response to the inquiry I sent to Castrol USA about where to get Castrol TAF-X in the USA: "Castrol TAF-X 75W-90 GL-4 gear oil is made in the U.K. and sold only in Europe. However, the equivalent in the U.S. is Syntorq LT. Having said that, Syntorq LT SAE 75W-85, API GL-4 is a premium high performance, synthetic gear lubricant for synchronized manual transmissions. The all new "clean slate" approach enables Syntorq LT to provide consistent performance and durability under the most severe operating conditions due to its unique polymer free formula. It has been designed primarily as a problem solving gear lubricant for manual transmissions to provide reduced gearshift effort at low temperatures. Syntorq LT is available through General Motors (Part #12346190) and Chrysler (Part #4637579) dealerships. Please contact your local dealership."

 

[MolaKule]

I would say the original spec was for a dino 70W90, so a GL4 such as MT90 (essentially a 75W85)would offer sufficient AW/EP protection.

See the Interesting Articles threads for a three-part series on Gear Lubes.

[ April 29, 2004, 12:35 PM: Message edited by: MolaKule ]

 

[MolaKule]

quote:

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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.

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Just an FYI:

The GM Synchromesh manual transmission fluid is now partially synthetic; GM is using a heavy parrafinic base oil with AB's and esters.

 

[Michael SR]

quote:

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Originally posted by MolaKule:
Just an FYI:

The GM Synchromesh manual transmission fluid is now partially synthetic; GM is using a heavy parrafinic base oil with AB's and esters.

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ya, but which one do you mean? last time i went to a GM dealer and asked for "synchromesh," the guy told me they have 3 parts numbers with that name on the bottle.

i think the high dollar one with "friction modified" written on the label is #12377916. the #12345349 is the one that looks, smells, and tastes (kidding) just like the pennzoil stuff at autozone. i'm not sure what the 3rd one is the parts fellow mentioned, but syntorq (#12346190) might say synchromesh on the bottle too.

-michael

 

[JohnBrowning]

Syntorque LT users Redline MT90 and Royal Purple Max Gear 75W90 can be used in place of this product according to each company.

 

[MolaKule]

Yo, Michael,

Part #12345349. Title is, "Synchromesh Transmission Fluid."

Now a quart black bottle with Blue and Silver labeling.

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