# Gearbox Oil question, Redline MT-90 too thin?



## hoodmeister (Jul 25, 2007)

I have a 2000 Jetta, VR6 with the 5 speed. Just did complete clutch job and replaced the old gearbox oil with Redline MT-90. Now 1st and reverse are hard to shift into. Since reverse has no syncros, it grinds a bit indicating that the clutch disc is able to spin-up the gearbox even with the clutch disengaged. If I start the car on a cold morning, 1st and reverse are fine, due to the thick cold oil stopping the gearbox from spinning. To me, this would indicate that maybe I need a higher viscosity oil in the gearbox. The new clutch may be dragging slightly and this issue may go away when the clutch gets broken in, but I wonder if the MT-90 (75W-90) is too thin. I searched a while for gearbox oil info, but didn't find anything that would help. Would VW dealer oil possibly be a higher viscosity? thanks!


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## saaber2 (Jul 15, 2008)

It could also be too slippery. Some of the redline fluids are friction-modified and some are not. It has been hit or miss for me using redline tranny fluids. For my old saab turbos Redline MTL made a night and day difference in shifting. For my old boxster S, I tried 3 different types of redline fluids (both friction modified and not) and none were as good as the stock fluid. I would try the stock fluid if only to reduce the number of variables. In other words, if you have the same issues with the stock fluid then you might have to look to something else as the source of the problem. My guess is the MT-90 may be too slippery or less than ideal viscosity, but just a guess.


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## BsickPassat (May 10, 2010)

75w90 is fine. MT-90 is a GL4 oil, so it will be suitable on the 02J tranny


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## gmikel (Nov 10, 2010)

*mt 90*

i use it in my 06 2.0 jetta. no problems, still hard to shift when below 20, but very smooth once warmed up.


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## jonyguitar (Nov 26, 2006)

*red line mt-90*

This is the final word on gear box lubes.....some know it all posted a blog on a VW site some where in cyber space suggesting that all gear box lubes for older manual 4 and 5 speeds jettas has to be GL-4 and nothing else because that was the designation when the cars were assembled! Using a GL-5...any GL-5 would be a mistake!.....This is so far from the truth it is laughable! Having spoken to many rebuilders at dealer ships and the VP's at companies like SuperTech oil, the following applies to any doubts you may have reguarding cheaper lube products.

1 All GL-4 lubes were upgraded to GL-5 for a reason! They meet higher standards for viscosity and meet all boil standards 130 degrees!

2 You cannot sell an upgrade unless it meets strict guidelines for GL lubrication formulas. The rebuilders and wrenches I spoke with all agree that GL-5 90 wt in any brand, is more than adequate for 4 and 5 spd transmissions that are not subject to extreme towing loads and or abuse....you would then look for a 90-140 wt.

3 All of the higher priced "performance" products do the same things but cost more for a reason....THEY WANT YOU TO SPEND MORE MONEY FOR THEIR PRODUCT..... ! Every one has to meet regulated standards! The guys that tear down and rebuild these gear boxes know they fail because the box was dry, not filled to capacity, abused and over heated. Brass metals are the problem, and rust easily, as the years roll on in the VW's we love! Thats why GL-5 had to address so many issues before approval! 

4 Any doubts you may have about this information can be verified by 10 google links or more for the document that is available to read for your selves. Government testing standards require that it be public knowledge for all who want clarification on the subject!


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## MarkusWolf (Dec 10, 2001)

jonyguitar said:


> This is the final word on gear box lubes.....some know it all posted a blog on a VW site some where in cyber space suggesting that all gear box lubes for older manual 4 and 5 speeds jettas has to be GL-4 and nothing else because that was the designation when the cars were assembled! Using a GL-5...any GL-5 would be a mistake!.....This is so far from the truth it is laughable! Having spoken to many rebuilders at dealer ships and the VP's at companies like SuperTech oil, the following applies to any doubts you may have reguarding cheaper lube products.
> 
> 1 All GL-4 lubes were upgraded to GL-5 for a reason! They meet higher standards for viscosity and meet all boil standards 130 degrees!
> 
> ...


Reason: GL-5 is allowed to contain sulfur as an extender, which will destroy *brass*. At least MK4 transmissions have *brass syncros*. GL-4 for my MK4.

Not trying to start a debate here, just letting you know why it is GL-4. eace:


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## harmankardon35 (Sep 16, 2009)

gl-5 is a better oil for its intended purpose. hypoid gears (differentials, NON synchronised transmissions) I know from experience that gl-5 causes synchroniser performance to degrade extensively, making shifting terrible in colder temperatures. gl-4 has about 'half' the additive pack which makes it better for synchro braking, but the viscosity is still too heavy in cold climates. This is where manual trans oils fit in. Robust enough to protect the gears and thin enough with the right additives to give good synchroniser performance. 

gl-4 was was not 'upgraded' to gl-5, gl-4 is still alive and well. It is just not as common due to low demand (how often do people change their gearbox oil? usually never..so you gotta look around for gl-4 if thats what your gonna use. )


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## gmikel (Nov 10, 2010)

:thumbup:


harmankardon35 said:


> gl-5 is a better oil for its intended purpose. hypoid gears (differentials, NON synchronised transmissions) I know from experience that gl-5 causes synchroniser performance to degrade extensively, making shifting terrible in colder temperatures. gl-4 has about 'half' the additive pack which makes it better for synchro braking, but the viscosity is still too heavy in cold climates. This is where manual trans oils fit in. Robust enough to protect the gears and thin enough with the right additives to give good synchroniser performance.
> 
> gl-4 was was not 'upgraded' to gl-5, gl-4 is still alive and well. It is just not as common due to low demand (how often do people change their gearbox oil? usually never..so you gotta look around for gl-4 if thats what your gonna use. )


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## BOUDAH (Aug 15, 2008)

You guys actually answered a few questions to an issue i had. I still want to research but this is a good start.


Also anyone that is knowledgeable on VW 4 motion and Quattro Rear Ends.....Those dont have "SYNCHRO's So based on the information above, would it be ok to use a GL-5 in the rear end or should i just play it safe and stick to a GL-4 Lubricant?


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