stick with G52 in your tranny - here's why...

Frank M

BANNED
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Apr 7, 2000
Location
NH
TDI
NB
LessIsMore said:
I see, so are you saying that one oil is the same as another? That also seems to be VWs possition, when they fill with ATF and spec 75w-90 in the manual.
I do not get that from what I have stated.. :)

However, if someone thinks one lube is the same as another, they will soon find out the truth.

Many manual transmissions used to use ATF. In recent years many manufactures have their own lube for both auto and manual transmissions and I have seen problems by not using them.
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
LessIsMore said:
If you drain a gear box and observe swirls of glitter in the oil, are you learning the same thing that an analysis will tell you or something better. IOW, does the analysis detect these large particles? If one oil drains black and another drains amber, should this info be treated as anecdotal, and therefore inferior to oil analysis? When I pulled the plug on my factory fill, the the plug was coated with a dark scum, as was the entire internal surface area of the gear box I imagine. How does the oil analysis account for this material?

I’ve only seen your G52 lab analysis and another one at BITOG. Yours was nothing to jump up and down about and the other one was flat out bad.
Peter - I just wanted to know what you based your opinion on. I do feel lab analysis is valuable.

FWIW - the other G52, the fully-synthetic G052171A2, lists for $34.07 per liter! Maybe it is the ultra-mega-super gear oil of all of our dreams - i don't know of anyone that's tried it in a TDI though...

supposedly, the fully-synthetic G052171A2 is what was in the MK5 GTI 6-speed manual i test drove the other day :D. that shifted fine - though i did miss one downshift (probably my fault).

cheers!
 

Frank M

BANNED
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Apr 7, 2000
Location
NH
TDI
NB
david_594 said:
..... Im running the G52 in my 2000 Jetta. Smoothe as melted butter when warm, but when it gets cold it feels more like a frozen block of butter.
Use G052 synthetic and it will be the best it can be when you have sub zero temperatures.
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
DD sent me some G50, and I just got the V@100c results back from the lab - 15.6 cSt.

Viscosity Comparison @ 100 C
(Manual Tranny Fluids)
16.7 = Motul MOTYLGEAR 75-90
15.6 = Redline MT-90 75-90

15.6 = VW G50 (synthetic)
15.2 = Mobil 1 Synthetic 75W-90
15.2 = Motul Gear 300 75-90
15.0 = Elf Tranself Synthese FE 75-90
14.9 = AMSOIL AGL 80W-90
13.8 = Amsoil MTG 75-90
10.6 = Redline MTL 70-80
9.6 = AMSOIL MTF Synchromesh Trans fluid (GM/Chrysler)
6.3 = VW G52 (mineral)

?? = VW G52 (synthetic - G052171A2) Anyone have some they can send me to get lab tested?
 

AndyH

Registered Vendor , w/Business number
Joined
May 25, 2001
Location
San Antonio, TX
TDI
'97 Passat Wagon 410K RIP
SUNRG said:
LOL - this is sooo true. my shifting was fine and fuel economy very good but here i am tinkering...

i can't help myself though!! :D

honestly - i've decided i really like the 14.0 cSt Motul Gear 300 that's in now!!!
Rob,

How much difference did you feel when you changed either to or from the G52 to the significantly heavier fluids?

Andy
 

LeeM

Veteran Member
Joined
Jan 26, 2003
Location
Hagerstown,MD
TDI
2015 Passat SE, 2002 Jetta Reflex Silver
SUNRG said:
Peter -
FWIW - the other G52, the fully-synthetic G052171A2, lists for $34.07 per liter! Maybe it is the ultra-mega-super gear oil of all of our dreams - i don't know of anyone that's tried it in a TDI though...

supposedly, the fully-synthetic G052171A2 is what was in the MK5 GTI 6-speed manual i test drove the other day :D. that shifted fine - though i did miss one downshift (probably my fault).

cheers!
The G052171A2 is the recommended gear box oil for all the Bora 6-speed transmissions I found listed in the Euro ETKA, be it for a gasser or TDI.
 

Frank M

BANNED
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Location
NH
TDI
NB
SUNRG said:
supposedly, the fully-synthetic G052171A2 is what was in the MK5 GTI 6-speed manual i test drove the other day :D. that shifted fine - though i did miss one downshift (probably my fault).

cheers!
I put it in my NB a couple of years ago.
It stopped my spyder gear hum and shifts excellent in sub zero temps..
 

AndyH

Registered Vendor , w/Business number
Joined
May 25, 2001
Location
San Antonio, TX
TDI
'97 Passat Wagon 410K RIP
Request for Info and Viscosity Caution

Folks,

I'd like to request that we include the year and transmission (especially if not the transmission the car came with when it was born). We're all commenting on how a certain product feels or performs in our car, but this info is basically meaningless with out knowing what the hardware is.

Tied to my first request/comment are these cautions:

- The first choice for any fluid should be one that meets the OEM required specifications and viscosity for your specific piece of equipment.

- Before one can select an alternate product, we must know the OEM requirement. The fluid properties, characteristics, and specifications were based on the engineering of the specific piece of hardware. Different transmissions will probably require different fluids.

Here’s a quick summary of what can happen if we experiment without proper info.

- A gearbox that was being monitored with oil analysis and vibration analysis failed catastrophically
- The gearbox was replaced with a new unit, refilled with fluid, and put on-line
- The replacement gearbox failed after two days of service
- The gearbox failed – twice – because ISO 680 viscosity fluid was used instead of the OEM recommended ISO 320 gear lube

Keep something in mind here – ISO 680 IS a recommended fluid for this gearbox – for a specific range of temperature and duty conditions. This was NOT a case where the operators decided to second-guess the engineers.

You can read the full article from this month’s “Practicing Oil Analysis” magazine on-line at http://www.practicingoilanalysis.com/article_detail.asp?articleid=849&relatedbookgroup=OilAnalysis&title=Confirm%20OEM%20Recommendations%20-%20Replacing%20the%20Problem%20May%20Not%20Remove%20the%20Problem

Bottom line for us TDIers: Those of us with older cars – with transmissions designed during a time when the industry was using ‘universal’ fluids – should stick with the recommended 75W-90 GL-4 synthetic. If we select a GL-5 fluid, we can expect synchronizer problems from either friction modifiers (slipping) or extreme pressure additives (sticking, corrosion). If we select lower viscosity fluids than recommended (such as G052726A2, Synchromesh, or ATF), we can expect higher rates of wear due to lower film strength – higher wear means more friction, more heat, earlier fluid failure, and shorter seal life. If we select higher viscosity fluids, we can expect a drop in fuel economy, more generated heat because of the extra work required to overcome the resistance of the thicker fluid, stiffer shifting both hot and cold, and sticky synchronizers as a start. We’ll also have increased rates of wear and can have early bearing failure because the heavy fluid can’t get into narrow passages as well as the proper fluid.

The ‘Lesson Learned’ from the Noria / Practicing Oil Analysis article is this: “Recommended lubricants should also be confirmed if in question. Case in point: this gearbox suffered a level of wear that could have been avoided. It is safe to say that much useful life was lost from this unit to this common error. While operating conditions may occasionally warrant the use of a lubricant other than that recommended by the manufacturer, the OEM recommendation should be strongly considered as the starting point. Careful testing and documentation should be conducted prior to making a viscosity change in any piece of equipment.”

“While it is widely understood that using a lubricant too low in viscosity will result in insufficient lubricant film, it is also important to understand that using a lubricant too high in viscosity can produce similar problems. In this case there was an apparent loss of lubricant film due to the reduced oil flow through small passages, which were designed for a lower viscosity lubricant.”

Andy
 
Last edited:

TooRoundTDI

Skunk Rocker
Joined
Jun 8, 2005
Location
Broad Brook, CT. I have vag-com, PM me.
TDI
1998 Jetta
I just put in Mobil 1 75w-90 in my tranny and dont really like it. I have a 1999 and I just noticed that the Mobil 1 is GPL-5 which I think is incorrect so that may be why. Its really hard to get into gear when its cold and I noticed in the above chart it is 15.3 so thats probably why. Im going to the dealer on monday to get the correct fluid and Ill count the Mobil 1 as flushing out my trans.
 

david_594

Top Post Dawg
Joined
Feb 28, 2004
Location
Cheshire, CT
TDI
2000 Jetta GLS Silver
Frank, do you still have any of this oil left over? If you do would you be willing to send out a sample for testing? If you dont want to/done have any I would be willing to order a liter of it to send out a sample from.

It seems like this would be the next logical step in our testing. Right?

Frank M said:
I put it in my NB a couple of years ago.
It stopped my spyder gear hum and shifts excellent in sub zero temps..
 

TDInownow

Veteran Member
Joined
Aug 27, 2003
Location
West End, NC (27376)
TDI
None right now...
I don't have much to add, but I'll chime in anyway. :rolleyes:

After looking through all the info here, I took the plunge and used the G50 when we did the 681...procured from worldimpex at a whopping $21 per liter. I read some negative reviews on the redline on other sites (non-TDI related) and figured I'd just bite the bullet.

What I will say is that I thought the old fluid in my '03 looked pretty good for 110k. But so the question is, was the factory fill for the '03 G50 or G52?

J.
 

Frank M

BANNED
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Apr 7, 2000
Location
NH
TDI
NB
david_594 said:
Frank, do you still have any of this oil left over? If you do would you be willing to send out a sample for testing? If you dont want to/done have any I would be willing to order a liter of it to send out a sample from.

It seems like this would be the next logical step in our testing. Right?
the pic of this empty container was taken a couple of years ago.
i have sent the container to the recyler.
sorry:eek:
 
Last edited:

Powder Hound

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Joined
Oct 25, 1999
Location
Under a Bridge, Crestview, FL, USA
TDI
'00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
SUNRG said:
...FWIW - the other G52, the fully-synthetic G052171A2, lists for $34.07 per liter! ...
The marketing guys at VW must be thinking that some suckers will buy anything.

Particularly when the "synthetic" label gets applied to group III and group IV bases, as well as the group V base (group V is the only thing you get from Redline), I think I will stay with the Redline I have been using in my '00 transaxle. MTL, no problems (leaks, shifting, notchiness, etc) for 160k miles. Since it is much more shear stable than anything else on the market, I don't anticipate ever changing it unless it decides to become a self machining device.
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
Update: The G52 that addressed the "spider gear humming" issue in earlier 02J manual transmissions is the synthetic G052171A2 that lists for $34.07 / liter (not the mineral based G052726A2).


thanks to karlaudi for sending me this TSB. karlaudi also noted that this Nov. 2001 TSB may have since been superseded.
 

TDInownow

Veteran Member
Joined
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Location
West End, NC (27376)
TDI
None right now...
Okay, so given the date of the TSB, should I believe that there was G52 (synthetic) in my '03 Jetta from the factory, or G50?

Wondering if I'll start to experience the spider-gear hum now with the G50 in there. What exactly should I be listening for?
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
TDInownow said:
Okay, so given the date of the TSB, should I believe that there was G52 (synthetic) in my '03 Jetta from the factory, or G50?

Wondering if I'll start to experience the spider-gear hum now with the G50 in there. What exactly should I be listening for?
these are good questions & i don't know the answers.

to me, it seems if you're going to spend the big bucks to get G50, the synthetic G52 is only a few dollars more and it may be the best bet.

my understanding is that some dealers do not carry G50 (special order only) and my local dealer has plenty of the synthetic G52 in stock, so maybe the G50 manual transmission spec. has been completely superseded.
 

dabear95

Veteran Member
Joined
Sep 26, 2002
Location
Roseville, MI
TDI
2002 Golf GLS, Silver
SUNRG said:
DD sent me some G50, and I just got the V@100c results back from the lab - 15.6 cSt.


Viscosity Comparison @ 100 C
(Manual Tranny Fluids)
16.7 = Motul MOTYLGEAR 75-90
15.6 = Redline MT-90 75-90

15.6 = VW G50 (synthetic)
15.2 = Mobil 1 Synthetic 75W-90
15.2 = Motul Gear 300 75-90
15.0 = Elf Tranself Synthese FE 75-90
14.9 = AMSOIL AGL 80W-90
13.8 = Amsoil MTG 75-90
10.6 = Redline MTL 70-80
9.6 = AMSOIL MTF Synchromesh Trans fluid (GM/Chrysler)
6.3 = VW G52 (mineral)

?? = VW G52 (synthetic - G052171A2) Anyone have some they can send me to get lab tested?

Thanks for the information. That validates the desicion I made in Jan - 2003 to use MT-90. It only improved upon my driving pleasure. Michigan, 2002 Golf.


Jason
 

pepper10

Veteran Member
Joined
Apr 21, 2004
Location
Manchester, NH, USA
TDI
:)2002 A4 TDI , 2006 A5:)
From AndyH's post above:"If we select lower viscosity fluids than recommended (such as G052726A2, Synchromesh, or ATF), we can expect higher rates of wear due to lower film strength – higher wear means more friction, more heat, earlier fluid failure, and shorter seal life. If we select higher viscosity fluids, we can expect a drop in fuel economy, more generated heat because of the extra work required to overcome the resistance of the thicker fluid, stiffer shifting both hot and cold, and sticky synchronizers as a start. We’ll also have increased rates of wear and can have early bearing failure because the heavy fluid can’t get into narrow passages as well as the proper fluid."

Using G52 would mean faster wear of fluid and components. Anyone can chime in on the accuracy of this statement?
 

karlaudi

Veteran Member
Joined
Aug 24, 2005
Location
San Francisco Bay area
TDI
2002 VW Golf GLS 1.9TDi; 2012 Volkswagen Golf 2.0 TDi
TDInownow said:
Okay, so given the date of the TSB, should I believe that there was G52 (synthetic) in my '03 Jetta from the factory, or G50?

Wondering if I'll start to experience the spider-gear hum now with the G50 in there. What exactly should I be listening for?
If you check your Bentley Manual / CD-ROM you will see that VW selects the grade of gear oil based (G50, G51, etc.) on the Transaxle used, as determined by the Engine code. As stated previously the viscosities are all the same. The TSB I supplied SUNRG came from my CD-ROM which was current through the 2002 model year. None of the transmissions listed used G52 as original fill, yet this TSB was included.

For information on the correct grade of gear oil, consult with your Dealer's Parts Department and / or get the latest Bentley Manual, either hard copy or CD-ROM. and / or contact VW since they willl provide hard copies of all current TSB's for $4.00 for the first copy and $2.00 each for additional copies. Robert Bentley Publishers, I believe, still provides updates for the CD-ROM Manuals for a nominal fee.

Also, please keep in mind that VW does not specify changing manual transmission gear oils as part of regular maintenance schedules, only checking and then adding fluid as needed.
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
...VW selects the grade of gear oil based (G50, G51, etc.) on the Transaxle used, as determined by the Engine code. As stated previously the viscosities are all the same.
this thread was started because the above is not true.

OEM G50 (synthetic) V@100c = 15.6cSt

OEM G52 (mineral / G052726A2) V@100c = 6.3

the difference is jeyegundo!

what we all want to know is:

OEM G52 (synthetic / G052171A2) V@100c = ??
 

AndyH

Registered Vendor , w/Business number
Joined
May 25, 2001
Location
San Antonio, TX
TDI
'97 Passat Wagon 410K RIP
Powder Hound said:
The marketing guys at VW must be thinking that some suckers will buy anything.

Particularly when the "synthetic" label gets applied to group III and group IV bases, as well as the group V base (group V is the only thing you get from Redline), I think I will stay with the Redline I have been using in my '00 transaxle. MTL, no problems (leaks, shifting, notchiness, etc) for 160k miles. Since it is much more shear stable than anything else on the market, I don't anticipate ever changing it unless it decides to become a self machining device.
Powder Hound,

Group III can be called 'synthetic' in the Americas, but not in Europe. Euro and Japanese 'synthetics' must be man-made base stocks - so Euro synthetics must be Group IV and/or Group V.

Andy
 

AndyH

Registered Vendor , w/Business number
Joined
May 25, 2001
Location
San Antonio, TX
TDI
'97 Passat Wagon 410K RIP
SUNRG said:
this thread was started because the above is not true.

OEM G50 (synthetic) V@100c = 15.6cSt

OEM G52 (mineral / G052726A2) V@100c = 6.3

the difference is jeyegundo!

what we all want to know is:

OEM G52 (synthetic / G052171A2) V@100c = ??
Rob,

I'm going to get a quart of both G052 products today and get samples to the lab. I want to know what the synthetic looks like, and I want a 2nd datapoint on the 6.3 cSt from G052726A2. I'm still very surprised the fluid's this thin.

Andy
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
AndyH said:
Rob,

I'm going to get a quart of both G052 products today and get samples to the lab. I want to know what the synthetic looks like, and I want a 2nd datapoint on the 6.3 cSt from G052726A2. I'm still very surprised the fluid's this thin.

Andy
awesome! & thanks!

FWIW - i drained the Motul Gear 300 yesterday and filled with Redline MTL. so far it shifting nice. it's real warm here so it may be a few seasons before it gets cold tested.

cheers!
 

karlaudi

Veteran Member
Joined
Aug 24, 2005
Location
San Francisco Bay area
TDI
2002 VW Golf GLS 1.9TDi; 2012 Volkswagen Golf 2.0 TDi
SUNRG said:
this thread was started because the above is not true.

OEM G50 (synthetic) V@100c = 15.6cSt

OEM G52 (mineral / G052726A2) V@100c = 6.3

the difference is jeyegundo!

what we all want to know is:

OEM G52 (synthetic / G052171A2) V@100c = ??

:eek: SUNRG, please. What is in VW's Service Manuals is quite clear.

VW and Audi do not tell you that to select the correct gear oil for your VW / Audi transaxle/transmission/ final drive you must first have an independent lab analysis first, before selecting the "correct" refill oil.

All the oils listed in the Bentley Manual, I previously referred too, are all listed as 75W-90 oil viscosities, regardless of the specification of G50 or G51, and as the oil(s) to be used in the transaxles of the models covered.

What determines what “grade” to use, be it G50 or G51, is the Engine Code. Which varies depending on the year and type of engine fitted. Of the 35 engine codes listed, only one transmission is identified – “5-speed, 02J".

Of the 35 Engine codes listed, for the models covered, 24 transmissions are determined to need “G 50 gear oil 75W-90 (synthetic oil)” and 11 are determined to need “G 51 gear oil 75W-90 (synthetic oil)” .

Consulting the ZF North America / ZF Friedrichshafen AG website reveals that even ZF selects transmission fluids based on OEM part numbers, almost exclusively, while referencing too select oil company names/part numbers.

For Example:

Product Groups: 5HP24, 5HP24A (1)

According to spare part number of vehicle manufacturer:
ZF Lifeguardfluid5 x
=> Audi Oil No. G 052162A1x
=> BMW Oil No. 8322 9407807x
=> Citroen Oil No. Z 000169756x
=> Jaguar Oil No. JLM 20238x
=> Mercedes Benz Oil No. A 0019892203x
=> Peugeot Oil No. Z 000169756x
=> Porsche Oil No. 999.917.547.00

(1) Fill differential and transfer box with gear oil Burmah SAF-AG4 (Audi / VW Oil No. N 052145000, Porsche Oil No. 999.917.545.00).

(2) Fill differential with gear oil API GL-5, MIL-L-2105D, MIL-PRF-2105E, SAE J 3260, SAE grade 75W-90 / 90.
x
Additives of any kind added later to the oil change the oil in a manner that is unpredictable, and they are therefore not
permitted. No liability of any kind will be accepted by ZF for any damage resulting from the use of such additives.



PLEASE REFRENCE for the above example:

Car Driveline
Technology
Manual and automatic transmissions for cars List of lubricants TE-ML 11
The list of lubricants TE-ML 11, Edition 01.01.2006 replaces all
previous editions. The current list can be requested from any ZF
after-sales service center or accessed on the Internet under
www.zf.com.
ZF Getriebe GmbH
Südring
D-66117 Saarbrückenx
phone: + 49 681 920-2497x
fax: + 49 681 920-2388



While it is fun to "tinker", taking a single oil analysis "fact" and trying to draw some conclusion about what “correct” oil is be used in a transmission without conclusive "proof" that the “original fill” gear oil is either the source of a present or future problem; when so little of the actual “properties” of the OEM approved fluids is little known; were there are no “control groups”; nor is a "tear down inspection" of the "test" transmission provided; it makes me wonder how you can draw the conclusion(s) you do beyond some desire to find some fault, any fault, with the VW “Factory method”.

Although, I am truly glad you having fun doing it! :)
 

karlaudi

Veteran Member
Joined
Aug 24, 2005
Location
San Francisco Bay area
TDI
2002 VW Golf GLS 1.9TDi; 2012 Volkswagen Golf 2.0 TDi
AndyH said:
Rob,

I'm going to get a quart of both G052 products today and get samples to the lab. I want to know what the synthetic looks like, and I want a 2nd datapoint on the 6.3 cSt from G052726A2. I'm still very surprised the fluid's this thin.

Andy
Around 1987 BMW began using ATF in their manual transmissions, and may still to this day, as I no longer keep current with BMW. Having a "thin" fluid is no suprise to me.;)
 

Frank M

BANNED
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Apr 7, 2000
Location
NH
TDI
NB
karlaudi said:
:eek: Of the 35 Engine codes listed, for the models covered, 24 transmissions are determined to need “G 50 gear oil 75W-90 (synthetic oil)” and 11 are determined to need “G 51 gear oil 75W-90 (synthetic oil)” .

Consulting the ZF North America / ZF Friedrichshafen AG website reveals that even ZF selects transmission fluids based on OEM part numbers, almost exclusively, while referencing too select oil company names/part numbers.
If I understand this correctly, when some one asks what should they use in their transaxle the best answer is to consult the manual..
telling other members that the lube they experimented with is good/better and they should use in their application is "bad advice"
 

pepper10

Veteran Member
Joined
Apr 21, 2004
Location
Manchester, NH, USA
TDI
:)2002 A4 TDI , 2006 A5:)
karlaudi said:
:eek: SUNRG, please. What is in VW's Service Manuals is quite clear.

VW and Audi do not tell you that to select the correct gear oil for your VW / Audi transaxle/transmission/ final drive you must first have an independent lab analysis first, before selecting the "correct" refill oil.

All the oils listed in the Bentley Manual, I previously referred too, are all listed as 75W-90 oil viscosities, regardless of the specification of G50 or G51, and as the oil(s) to be used in the transaxles of the models covered.

What determines what “grade” to use, be it G50 or G51, is the Engine Code. Which varies depending on the year and type of engine fitted. Of the 35 engine codes listed, only one transmission is identified – “5-speed, 02J".
So what about people, like myself who complain of hard shifting in cold weather with the OE fluid??? Am I condemned because the manual states to use G50? I don't think so...:rolleyes:

And what about dealers now stocking G52 and putting it in 02J transmissions where the manual also states G50!!??? Obviously, G52 is compatible with older 02J transmissions where G50 was specified otherwise there would be a warning on the bottles or VW would have warned dealers of the consequences. They even put out a TSB for the gear whine fix prescribing switching to G52! The manuals are not always correct.:rolleyes:

Reality is that there is one thing that is necessary for these transmissions: a GL-4 fluid. It's viscosity is not a mandatory parameter.
 

SUNRG

Top Post Dawg
Joined
Oct 19, 2003
Location
Roanoke, VA
TDI
None currently. Previously owned 04 Golf TDI & 05 Passat GLS Wagon TDI
While it is fun to "tinker", taking a single oil analysis "fact" and trying to draw some conclusion about what “correct” oil is be used in a transmission without conclusive "proof" that the “original fill” gear oil is either the source of a present or future problem; when so little of the actual “properties” of the OEM approved fluids is little known; were there are no “control groups”; nor is a "tear down inspection" of the "test" transmission provided; it makes me wonder how you can draw the conclusion(s) you do beyond some desire to find some fault, any fault, with the VW “Factory method”.
karlaudi - you and i don't disagree. from my initial post:
TITLE: stick with (OEM) G52 in ur tranny - here's why...

If your transmission specifies G52 fluid I highly recommend sticking with it as opposed to changing it out for one of the popular/common replacement manual transmission fluids because the viscosity of G52 is much thinner:
Viscosity Comparison @ 100 C
10.6 = Redline MTL 70-80
13.8 = Amsoil MTG 75-90
15.2 = Motul Gear 300 75-90
15.6 = Redline MT-90 75-90
15.0 = Elf Tranself Synthese FE 75-90
16.7 = Motul MOTYLGEAR 75-90

6.3 = OEM G52 (part numbers G052726A2 / G05272601)
**the 75-90 viscosity of common gear / manual transmission oils is IMO not suitable for use in VW transmissions where G52 is specified.**
i am not recommending second guessing VW. i've repeatedly posted that my shifting with G52 was just fine. i personally am experimenting with some other manual transmission fluids - but i'm not recommending that anyone else does. i have stated that IMHO if someone was bent on going with something other than OEM mineral G52 that Redline MTL seems like it may be the most similar after-market option.

you wrote:
(G50, G51, etc.) ... As stated previously the viscosities are all the same.
i took "etc" to mean G52, and the viscosity of G52 is not the same as G50 or G51 - that's all.

you've been referring to your 2002 Bentley Manual. below is page 34-15 of the 2005 Bentley. regarding the two G52s (mineral and synthetic) it states "Viscosity is not specified for either gear oil." i have had the mineral G52 repeatedly lab tested (used sample tested 4x, new sample tested 2x) and its V@100c is 6.3cSt or very close to that. because it is clearly NOT a 75w-90 gear oil i've recommended "sticking with OEM G52 if that's what your transmission specifies" because as AndyH has stated, using a fluid that's significantly thicker than what is OEM specified can decrease performance and increase wear.



 
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