Question about GL4 vs GL5 gear oils.

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The use of dual rated (GL4 and GL5) oils in synchronized manual transmissions is controversial and people will argue forever about it.
Personally i wouldn't do it.
Reasons: GL5 diff oils have increased amounts of friction modifiers to ensure slipperiness; these can interfere with synchro function. Also, the old saw about increased EP agents that can damage yellow metal synchros....
All you might notice is notchier shifting.

Charlie
 
I just want to say, Ford Motorcraft GL-4 rated XT-M5-QS is the bees knees.

From my understanding from what I've read on another forum, it's the cst 100 rating that is really important. The Ford stuff is thicker than the thinner Syncromesh fluids but thinner than the other GL-4 fluids like Amsoil's and Redline's. Which is why a lot of people that use it in the Mazdaspeed's like it so much. You get the better shifting of a thinner fluid than Redline's and Amsoil's but not so thin you lose out on protection like in the Synchromesh fluids.

These are just my observations from another forum on MS's that use a tranny that calls for a GL-4 75w90 fluid. There are quite a few people there that have tried all of the above and settled on the Ford stuff for that car. There are people that also run Sychromesh fluid for it too that have tried all of the above and agree it shifts the best on Synchromesh, especially in the cold, which makes sense. But for me, it's just too thin and I don't want to go that thin and lose protection.

By the way, from those links above, it's my understanding Molakule is saying those specs are really old and outdated and since 2000 GL-5 fluids are perfectly safe for the yellow synchro's that call for GL-4 fluids and that any mismatch only comes from viscosity (sorry, I forget the other thing). But it seems his point was that GL-5 was the way to go but to find a fluid in the viscosity range (using cst 100) and the other thing he mentioned but not to worry about those fluids eating away your bronze parts. In fact, he seems a bit frustrated by the API's laziness in updating the specs to reflect all this.
 
You will want to read this thread as well:

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1231182#Post1231182

In strictly technical terms, many modern GL-5 differential lubricants should offer the same or better gear protection in differentials than GL-4's for the hypoid differentials.

When one discusses GL-4 lubricants, it usually refers to Manual Transmission (MT) lubricants with special friction modifiers for synchro engagement.

If a gear lubricant manf. says it's product is backward compatible or covers both GL-4 and GL-5 protection categories, they are usually NOT discussing MT lubes but are referring to differential lubricants.

Proper viscosity CAN make a difference for cold weather shifting, especially for the Nissan transmissions in which I have a lot of experience.
 
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interesting.

Im going to attempt to gather the specs on all these different oils.
 
Quote:
Ford Motorcraft GL-4 rated XT-M5-QS is the bees knees


You might also want to try the GM Synthetic Manual Transmission Fluid, # 12346190. And it IS a real synthetic MT fluid with PAO's and esters and none of the pseudo-synthetic GroupIII oils.

It was specially designed for cold weather shifting.
 
Originally Posted By: MolaKule

If a gear lubricant manf. says it's product is backward compatible or covers both GL-4 and GL-5 protection categories, they are usually NOT discussing MT lubes but are referring to differential lubricants.


This is the product i was looking at that prompted all these questions and researching i had.

The discription says:
'Fully synthetic gear oil, for use on the street or the track
MOTUL Gear 300 is a 100% synthetic lubricant for gearboxes and axles Specially developed for competition cars: racing circuit, rallies, endurance trials. In all types of cars, under all conditions of use, this oil has proved its qualities and resistance to extreme pressures.'

73165_x600.jpg

73164_x600.jpg


There is also this one by Motul.
25301_x600.jpg



The bottom line is i have no idea what to use.

I see tons of stuff saying the OEM VW gear oil for the 020 transmission is thinner than a 75w90. Yet they specify a GL-4 75W90.

Then i see stuff about VW/Audi guys using and loving synchromesh. Which is clearly not a 75w90.

While all this is going on. No one EVER mentions that they just use the OEM fluid. Most people recommend Redline MT-90. But it has mixed reviews among the VAG community.

So im at a loss.
 
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Kaie, you can use just about whatever you want. The automakers are pretty much clueless when it comes to what is required by their own manual transmissions.

Some owners won't use the OE fluid because the dealer network is clueless too. So much superseding with PN's confuse the slave laborer at the parts counter. And, the automakers are on an MPG and shift quality push. So, each revision of the OE fluid tends to go thinner, which might not be optimum for an old transmission.

If they specify a GL4 fluid, use it. Since they recommend a 75w90, you should stick close to it.

Since your weather is mild, you can go a little thinner if you want. Any of the 75w85 GL4 gear oils should work fine.

Easy to get online choices are Redline MT85 or MT90 & Amsoil MTG. Idemitsu also has a full synthetic MTF that is 75w90.

You can use a GL5 gear oil too, but are not optimal if they have LSD additives. Some GL5 gear oils, without LSD additives and/or synchro safe, are the Eneo 75w90, Silkolene Silktran, Redline 75w90NS, Motul Gear300, Lubro-moly, Torco RTF, Ford, Subaru...

GL4 75w90 is available at Ford dealers. Nissan, Kia, GM, Hyundai, Chrysler dealers have 75w85 GL4.

Since fluids shear with time, the new gear oil you install might take a few thousand miles to 'loosen up'. Be patient with whatever MT you choose.
 
It's been pretty cold the last couple winters... last few weeks has been lows in the 20s and high 30s-low 40s as highs.

Ive noticed very stiff shifting while its been cold

Do you think using like a synchromesh in the winters and a normal 75w90 in the summers is too much fluid changing? Ive owned the car for 5-6 years and have put 70k on it. So i dont get THAT many miles in a year.
 
Years ago Porsche came out with a tech bulletin that superseded GL4 to GL5 for all manual transmissions. The part I don't understand is that the 944 used a modified Audi trans. that called for GL4 only. And yes it had brass syncros.
 
Originally Posted By: Kaie


Ive noticed very stiff shifting while its been cold

Do you think using like a synchromesh in the winters and a normal 75w90 in the summers is too much fluid changing? Ive owned the car for 5-6 years and have put 70k on it. So i dont get THAT many miles in a year.



When cold its always more difficult to shift. THIS IS NORMAL.

I'd recommend a 75w85 and change it every 2-3 years.
 
Originally Posted By: MolaKule
Quote:
Ford Motorcraft GL-4 rated XT-M5-QS is the bees knees


You might also want to try the GM Synthetic Manual Transmission Fluid, # 12346190. And it IS a real synthetic MT fluid with PAO's and esters and none of the pseudo-synthetic GroupIII oils.

It was specially designed for cold weather shifting.

Fantastic... thank you, will do. Any chance you know the 40 and 100 cSt values or a link to the PDS by chance? Just more curious than anything as I've already ordered based on your recommendation here. My new tranny has about 3k miles on it so far, is this a good mileage to switch out to the new GM stuff or should I wait a bit more? TIA
 
Quote:
Anyone have a link to the Product Data Sheet for the GM Synthetic 12346190 fluid? Or know the kv 40 & 100 cSt values?


75 and 11.5 cSt, respectively.
 
Sorry, one more. The Flashpoint and Pour Point (c) and Viscosity Index? I'm putting together a comparison on the mazdaspeed forums of all the available GL4 fluids. I'll post it here to.

Thanks btw!!
 
Spec wise so far the Red Line MT-85 is looking a bit better than the GM stuff. It's a true synthetic group iv & v also, right? Just wondering how the GM stuff is rated a 75w89 while the MT-85 is a 75w85 when the Red Line is actually a bit thicker at kv 100 cSt.

Here's what I got so far btw...

GM Synthetic MTF 12346190:
GL-4 75w90 ===== kv 40 cSt: 75, kv 100 cSt: 11.5, VI: , PP (c): , FP (c):

Red Line:
D4 ATF ======== kv 40 cSt: 34.0, kv 100 cSt: 7.5, VI: 198, PP (c): -60, FP (c): 225 ( GL-4 MTL 70w80 == kv 40 cSt: 56.2, kv 100 cSt: 10.6, VI: 183, PP (c): -50, FP (c): 232 (max)
GL-4 MT-85 75w85 = kv 40 cSt: 64.3, kv 100 cSt: 12.0, VI: 172, PP (c): -48, FP (c): 236 ( GL-4 MT-90 75w90 = kv 40 cSt: 90.0, kv 100 cSt: 15.6, VI: 185, PP (c): -45, FP (c): 240 ( GL-5+ 75w90 NS == kv 40 cSt: 95.0, kv 100 cSt: 15.6, VI: 176, PP (c): -45, FP (c): 221 ( GL-5 75w90 ===== kv 40 cSt: 115., kv 100 cSt: 16.4, VI: 155, PP (c): -45, FP (c): 227 (
Ford Motorcraft XT-M5-QS:
GL-4 75w90 ===== kv 40 cSt: 76.0, kv 100 cSt: 15.4, VI: 211, PP (c): -54, FP (c): 186

Amsoil MTG:
GL-4 75w90 ===== kv 40 cSt: 84.5, kv 100 cSt: 14.7, VI: 181, PP (c): -46, FP (c): 204
 
Don't forget Castrol Syntrans 40C 64.4 100C 11.8 VI 184 pour point -60C FP 208
and Mobil Delvac Synthetic Trans Fluid 50 40C 132 100C 17.5 VI 146 PP -45 FP 221

Charlie
 
Wow, that Castrol Syntrans specs are fantastic! The Mobil stuff, I'm not to sure about. Look at that huge spread on the kv but small viscosity index and so-so pour point. I'm wondering if they're using a lot of viscosity index improver's (?) or something. I don't think I would use that stuff. But I have to say those Castrol Syntrans specs are mighty impressive.

The one thing I don't like about the GM stuff is the rather high kv 40 cSt spec, but other than that they look great. Not sure if I want to go with this in my new transmission or that Castrol Syntrans stuff. Molekule, what's your opinion on it?
 
They aren't relying on any VIIs in the Mobil Syn Trans Fluid 50. I'm using it in my U500 in the hot Australian climate. I'll switch back to Syntrans when I get back to Alaska. The trans runs ~30F. hotter in Australia, about equal to the difference between the viscosities ( 180F. vs 150F.). Graph them and you'll ~parallel curves 30F. different.
Even though the Syntrans meets the Unimog spec 235.4, I've heard the Mobil stuff works well even in Canada.

Charlie
 
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