Gl4 vs. Gl5

 

^^^^ that is too funny! They are giving opposite answers! One says gl4 is for limited slip, the other says gl5 is for ltd slip. The first one says gl5 is not backward compatible, the second says it is! My research tells me this: do not use gl5 in our manual trannies as it will damage the yellow metals.

 

Everything gives contradicting answers, I check all of the documentation that comes with the car and there is no mention of this in it. I check in the service section of the manual (ELSA) and it claims it takes SAE 75W/90 synthetic in the transmission (part number G 052 145 S2) and final drive of the automatic which is in the same case as the Automatic but uses different oil. The rear differential is not mentioned in the maintenance section. In the repair section of the manual it lists the manual transmission and the rear differential use SAE 75W/90 in both (part number G 005 000). Even the factory doesn't seem to know what should go in these cars either. I wish the factory information included if the fluids were GL-4 or GL-5 because this is what makes the biggest difference.

 

ok, after closer inspection of the bottles, i can add some info.
each fluid has both a part number AND a material number.
Part # G 052 145 S2 (diff oil) is
Mat # G 052 145 3H

Part # G 052 911 A2 (tranny oil) is
Mat # G 052 911 3H

also, the Canadian sticker on top of the german sticker on the diff oil states API GL-5 (tadaaaaaaa)
while the tranny oil does not state any specs.
neither state any specs on the original german stickers underneath.

now for the REALLY confusing info (not even sure if i should post this, but i will.)

the canadian sticker on the diff oil calls it "Axle Oil" in english and in french calls it "Huile de differentiel"

BUT

the german sticker under it has multiple languages, and in english calls it "Gear oil - for manual and automatic gearbox" and in french calls it "Huile de pont - pour boites mecaniques et automatiques"

i am not sure why the canadian and german stickers have different labels in both english and french.

The tranny oil only has a german sticker, and the english calls it "Transmission Oil" (thank god) and the french calls it "Huile de boite"

I really hope that i have not caused more confusion than this all deserves lol!

 

Guys, GL-5 is widely touted as causing problems for yellow-metal gears - brass-syncro tranmissions should run GL-4. GL-5 is usually fine in stuff like differentials, where there is no yellow metal.

That said, if you're going to mess around with fluids, you need to do some research. A 75W-90 of one type does not necessarily have the same viscosity of a 75W-90 of another type. Fluid dynamics of lubricants is insanely complicated, thus following real-World testing is prudent. Run something that enthusiasts have been running for a while and know performs well.


This is not logical. Manufacturers always have a 'simple' guideline for everyone to follow, precluding them from having 20 pages of information for different types of fluids. Ideally, how I drive my car, and my climate, should dictate which fluids I use, not some Universal average deemed acceptable by OE Engineers. Also, there is continuous advancement in Science and Engineering, rendering past data obsolete. The factory gear oil chosen for my TT was likely done 15 years ago - a lot has changed since then. Furthermore, OEs can't real-World test the way enthusiasts can. We can take a single type of transmission and run every different fluid, in thousands of cars, for millions of miles, in every climate in the World.

I prefer Motul and Redline fluids; and, GM Syncromesh is said to be very effective at reducing syncro grinds.

 

My opinion is logical though because unless you are driving your car outside of regular conditions everything I wrote applies. All oils are also based on standards so even if things change they are usually included in the next revision but the general properties apply. Unless you are going to take your transmission apart and find out what it is made of the safest bet is to use factory because it is designed to work with what you have. Some oils do not protect as well or they can damaged your transmission and if you have done enough research to see what other people use you have also read about people having problems as well or at least I have.

What is important is using the correct formula such as GL-4 and GL-5 and once you know this you can try any brand because you know it is designed to work with what you have. I was only commenting that if you don't know if it is GL-4 or GL-5 you should stick to what you know will work or you could pay for it down the road.

 

Well, obviously the diff takes gl-5... I suspect that due to the brass synchros that the tranny is using gl-4, and likely this is the reason for 2 different oils.