GL5 gear oil bad in tranny,fact or myth?

[aquariuscsm]

This is a question I`ve been pondering for quite some time. Is GL5 gear oil (example,Mobil 1 75W90) really bad for a manual transmission,or is it an old timers myth? Reason I ask,is because recently when I was in a Nissan dealership buying an oil filter,I was talking to the service manager about oil,etc (he drives a 92 300ZX twin turbo w/almost 400k miles on it). I asked him about the best manual transmission fluid to put in it,and he said ANY 75W90 will do,regardless if it`s a GL4 or GL5 and that GL5 gear oils are perfectly safe and won`t harm a thing at all.

Ok experts,what`s the verdict on this one??????????

 

[Saturn_Fan]

In my 95 Nissan pickup I was warned to stay away from GL-5 at all costs. has something to do with the corrosive effects of it on certain metal parts and synchros in there. I went with GL-4 in the transmission, but went with GL-5 in the rear end. A guy on the Nissan forums said he has seen a few transmissions fail as a result of using GL-5. Whether this is forum banter is not known, but I didn't want to take a chance on it.

 

[MolaKule]

Gee aquariuscsm, where have you been?

Quote:
Differential lubes use friction modifiers to reduce mechanical and fluid friction and add some anti-shudder friction modifier for limited slip, both very different chemical compounds.

Manual Transmission fluids use a different friction modifier for synchro engagement, a modifier that does NOT contain the same chemical compounds as do differential lubes.

Both lubes contain the same EP additives, just in different strengths or additive ratios.


Most manual transmission "specific" fluids (GL4) contain about 40% to 60% of the EP additive of differential lubes (GL5) with inactive or buffered sulphurs. GL4 has come to infer a gear lube with the above percentages of EP additive. The exception of course is ATF fluid used in some of the newer transmissions.

You also have to consider the viscosity of the fluid that the transmission was designed for. The spectrum now ranges from ATF to 75W90 viscosities.

Ever since the synchromesh-type fluids appeared on the scene (such as the GM Synchromesh fluid), drivers have had better shifting due to better synchro engagement, attributed to the specialized friction modifier used in these lubes. This specialized friction modifier is better for metallic and composite synchros in terms of shifting and life.

A diffy 75W90 (GL5) usually has a higher viscosity than does an mtl in the same advertized weight.

SO a differential lube may not kill your tranny, but it is not the optimum lube.

 

[Kitto]

I have a question about Castrol Hypoy C Gear Oil 75W90
http://www.castrol.com/castrol/sectiongenericarticle.do?categoryId=9012228&contentId=7036192
It said in the product data sheet: "provides superior low temperature performance for smoother gear shifting and differential operation in colder climates."
Smoother gear shifting?? It is not MT-1 rating so it should not referring to truck transmission. Is it talking about car's transmission? Will this GL-5 be safe in tranny?

 

[MolaKule]

Look at the viscosity spec for the Hypoy C; it is 17.5 cSt at 100 C. Most 75W90 mtl specific fluids have the same spec listed at about 13.0 to 14.5 cSt. How do think this fluid would perform in cold weather when it's much thicker?

And there is no guarantee this fluid has the friction modifiers necessary for smooth shifting.

As I said above, mtl specific fluids are much better for your tranny. Recommend you check the viscosity requirements for your vehicle and find an mtl specific fluid.

 

[mechtech2]

MolaKule said it all in his posts - short and sweet.

But for emergency use or no other options, you won't break your transmission with GL5 .

 

[Kitto]

Originally Posted By: MolaKule

Look at the viscosity spec for the Hypoy C; it is 17.5 cSt at 100 C. Most 75W90 mtl specific fluids have the same spec listed at about 13.0 to 14.5 cSt. How do think this fluid would perform in cold weather when it's much thicker?

And there is no guarantee this fluid has the friction modifiers necessary for smooth shifting.

As I said above, mtl specific fluids are much better for your tranny. Recommend you check the viscosity requirements for your vehicle and find an mtl specific fluid.

oic, thanks a lot! I hope to find some dino MTL spec fluids but seems like this is impossible... that's why I am thinking about using Hypoy C to substitute.

 

[cheetahdriver]

some GL4 dino oils..

Pennzoil Gearplus GL4 (not the GL5 version)
Valvoline Duragear 75W/85 GL4

 

[widman]

Back to the original question, GL-5 or GL-4 depends on the synchronizer design and surface area, not to mention the aggressiveness of some unbuffered additives.
Since the GL-4's have half of the additives, they grab better and don't pull as much bronze off the synchronizers as they go. A lot depends on the surface area, angle/size of teeth, and pressures.

 

[heathenbrewing]

The OEM fluid is GL5 in my MT. They recommend using GL5, as per owners manual instruction. I called 'em on it and emailed the company directly - they told me "GL4 will extend the service life of your manual transmission over GL5".

So I put in Redline GL4 @ 9K mi. - tranny shifts much smoother and slightly quicker, almost "falls" into gear now.

Dealer recs are a "one-size-fits-all" mentality. Take it as a recommendation only. Do your own research. Im sure Toyota would rather stock 1 fluid (GL5) over 2 different ones. Most likely an economic decision. As said, GL5 may "work" in a MT, but may not be the best choice.

 

[mikered30]

Over on the corolla forum, people have reported problems with the GL5 fluid, transmission is specd' for GL4.

 

[wileyE]

Some transmissions or trans axles turn the power 90 degrees through a bevel gear, they usually spec gl 5. Subaru, for example.

 

[wantin150]

My Matrix tranny hated GL5.

 

[Tremo]

Very interesting. I have an 04 Outback with the 5-speed, and the manual calls for GL5 in both the front transaxle and the rear diffy. It cautions NOT to use anything with limited slip additives in the transaxle, but they're OK in the rear.

The shifting on the thing is a bit klunky, and it really does not want to shift into first gear if the car is moving much above a crawl. If you try to shift into first when you're rolling at 10 MPH, for example, there's a lot of gear grind. Is this normal for Subies?

 

[bulwnkl]

More or less.

 

[aquariuscsm]

Originally Posted By: Tremo
Very interesting. I have an 04 Outback with the 5-speed, and the manual calls for GL5 in both the front transaxle and the rear diffy. It cautions NOT to use anything with limited slip additives in the transaxle, but they're OK in the rear.

The shifting on the thing is a bit klunky, and it really does not want to shift into first gear if the car is moving much above a crawl. If you try to shift into first when you're rolling at 10 MPH, for example, there's a lot of gear grind. Is this normal for Subies?


Standard trannies from what little I know about the mechanics behind them are designed not to be shifted into 1st gear unless you`re at a complete stop.

 

[sprintman]

Tremo I changed our Outback 5-speed over to Redline 75W90NS. Massive change. 75W90 in the diff and D4ATF in the p/s.

 

[ewetho]

If the spec a difference I'd use the GL-4. I tried GL-5 in my 90 Swift (Thought it was like oil the new spec is better right???) and it hated it. Got gear clash right away. I went over to Redline MTL all I could find at the time and it was fantastic.

Since then GL-4 goes in GL-4 and GL-5 goes in the Diff!!!!

 

[Tremo]

Originally Posted By: sprintman
Tremo I changed our Outback 5-speed over to Redline 75W90NS. Massive change. 75W90 in the diff and D4ATF in the p/s.


I have enough of that 75W90NS to do the change on the front, but some jackoff put the drain plug on so [censored] tight that I can't get it loose. Serious. I used a 2' breaker bar on the T70 torx and the breaker bar was bending. The drain plug won't budge. I'm taking it into the dealer for them to deal with it.

As far as PS fluid goes, I'd be using the Valvoline Synpower stuff. I use it in my old IROC and it's great. Actually since the IROC has 130k on the clock, I use a 50/50 mix of Valvoline Synpower and Maxlife PS fluids. Since the Subie isn't "HM" yet, I'll skip the Maxlife on it.

I'm actually thinking of adding a bit of Royal Purple synchromax to the front transaxle to see if it helps with the shifting klunkyness. Or perhaps some RL MT90.

 

[artificialist]

D4 ATF in the P/S sounds good if the vehicle calls for ATF there.
If it doesn't, Redline makes synthetic PSF.