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What's the truth about GL-4 M/T oil?


1994SEV6
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I got my M/T into my truck. I got some rainwater in the trans while it was sitting. I wanted to replace the fluid anyway.

Around here, I read that I NEED GL-4 gear oil and NOTHING else will work. GL-5 will eat my synchros or something?

 

This is my first car, I don't have a lot of money, and I want to keep it for a long time. Therefore, I don't want to be destroying my synchros or anything.

 

I know that Redline and Amsoil make a really good Gl-4, but I can't find those locally. I wanted to get them in person to get them sooner, and I hoped to buy them from Advance Auto Parts so I can use the coupons.

Advance Auto Parts doesn't have anything that's Gl-4, all they have is Gl-5 and Gl-5/Gl-4.

 

I called up the dealer. I wasn't planning on buying gear oil from them, I just wanted to see if they know where I could get it. They told me that GL-4 was an outdated fluid and that I was going to be tricky to buy. He told me that GL-5 WILL work. When he told me this I lost all confidence in him and quickly got off the phone.

 

I called up NAPA auto parts since the employees there are miles better than AAP, Pepboys, or Autozone.

A very nice and extremely knowledgeable gentleman answered the phone. I explained my situation of needing GL-4 and NOT Gl-5.

He went back and checked. He had a no-name gallon of Gl-4 for sale for $36. He said that Amsoil was the best oil in the industry and Mobil 1 is a close second. He told me some stories about how his high school buddy is an industry chemist specializing in lubrications and he told me all about the advertising BS of oils and whatnot.

 

Then he told me the same thing the dealer told me. Gl-5 SUPERSEDES Gl-4. It's like DEXRON. DEXRON VI is compatible with DEXRON I, II, III, IV, and V. He told me that I can use GL-5 no problem. This guy proved his knowledge and experience. I wanted to believe him, but I really don't want to break my transmission.

 

What's the real story?!

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GL-5 fluid offers better protection in differentials. Generally when a manufacturer specifies that the fluid is GL-4 and GL-5 compatible, they are referring to use in differentials.

 

Additional reading:

 

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1157073

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

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1137238

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Gl5 in my transmission...yes I've had syncro problems but they were there when i bought the truck 12 years ago...granted I swapped transmissions about 3 years ago for my engine swap my syncros had not gotten any worse...that transfer had about 275k miles on it...the one in here now has about 180 k and it has the same issue with grinding occasionally in 4th gear but hasn't gotten any worse over time and I have yet to rebuild a transmission.

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Gl5 in my transmission...yes I've had syncro problems but they were there when i bought the truck 12 years ago...granted I swapped transmissions about 3 years ago for my engine swap my syncros had not gotten any worse...that transfer had about 275k miles on it...the one in here now has about 180 k and it has the same issue with grinding occasionally in 4th gear but hasn't gotten any worse over time and I have yet to rebuild a transmission.

 

I read something on bobistheoilguy.com about SOME gear oils eating the "yellow metals". Some gear oils don't?

Just curious, what are you using?

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Also worth mentioning to make sure u fill from the shifter BC the fill hole is in the wrong location

Oh yeah definitely. It's like 10x easier to fill from the shifter anyway

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GL5 has something GL4 doesn't, sulphur? Phosphorus? I can't recall, but it is documented here with links, articles and testimonials; what ever it is, it eats at the brass components, causing them to fail.

 

87pathfinder (let me look it up, the guy with the exocage SAS pathy) runs a heavy weight Amsoil product that isn't specified as GL-4 but doesn't have that ingredient and it works fine for him. At the end of he day, why gamble?

 

B

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GL5 has something GL4 doesn't, sulphur? Phosphorus? I can't recall, but it is documented here with links, articles and testimonials; what ever it is, it eats at the brass components, causing them to fail.

 

87pathfinder (let me look it up, the guy with the exocage SAS pathy) runs a heavy weight Amsoil product that isn't specified as GL-4 but doesn't have that ingredient and it works fine for him. At the end of he day, why gamble?

 

B

Yes. I don't want to gamble, but I can't find GL-4 anywhere. Napa has some Gl-4, the thing is, it's called "Napa Oil". They want $36 for a gallon, and that seems fair, but should I use it? I don't want to spend $36 on a sub-quality oil.

Edited by 1994SEV6
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http://www.amazon.com/Red-Line-50304-Manual-Transmission/dp/B000CPCBEQ/ref=sr_1_1?ie=UTF8&qid=1324747505&sr=8-1

 

Is it GL-4? Yes. Is it spendy? A bit. Will you feel better knowing your yellow metals are not being eaten? Maybe, I know I did. The previous owner of my Pathy ran a GL-5 (she just changed all the fluids and gave me the extra stuff) so I came home and bought the Redline. I feel better knowing its in there, and it shifts so much better on cold mornings.

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For those that like to read from authoratative sources:

 

http://www.api.org/certifications/engineoil/pubs/upload/1560.pdf

 

http://www.amsoil.com/articlespr/2007/article_gearoilbasics.aspx

 

I have found conflicting info on the net as to whether or not the sulphur content is corrosive to the brass synchros. I'd be inclined to avoid the GL-5 just in case.

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Okay I have FIRST HAND experience with it. GL-5 WILL EAT YOUR SYNCHROS!!!!! lol. I can't make it any more clear. There ARE specially marked GL-5 'type' gear oils that if you read on the back will say "also suitable for GL-4 vehicles" like the Redline MT-90 (which I recommend). I have used GL5 for as little as a month before I knew better and then I stumbled upon some startling info. Went to drain my transmission and it was gold flake gear oil. Not very comforting, although it was VERY pretty looking. Would have made a wicked paint colour!! hahahaha. So ya that 240sx 5 speed got swapped for another one about a year later as it wouldn't go into gear.

DO NOT USE GL-5!!!!!!!!

I don't care how cheap you are, don't use it. I guarantee it will cost way more to swap your trans later!

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the local napa where im at had Pennzoil synthetic GL-4 but it was not cheap. 12$ per litre I believe. But i mean really how often do you have to change your gear oil? cough it up and do it right... works great though and shifts much smoother than stock fluid.

Edited by Nefarious
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Yes. I don't want to gamble, but I can't find GL-4 anywhere. Napa has some Gl-4, the thing is, it's called "Napa Oil". They want $36 for a gallon, and that seems fair, but should I use it? I don't want to spend $36 on a sub-quality oil.

Napa seems to have quality items rebranded for them. I can't vouch for the oil, but I know their oil filters are made by Wix and are top notch. I suspect it would work just fine. If you buy a gallon, throw in 1 quart of Lucas oil stabilizer and you have about the right fill amount.

 

Here, the cheapest I could find, and it is 85w90 not 75w90. When I put 85w90 in my first pathy, it shifted hard into 1st and 2nd for a mile or two on cold mornings (35 degrees) but otherwise worked fine...

 

http://www.wayfair.com/CRC-1-Gallon-Hypoid-GL-4-Multi-Purpose-Gear-Oil-SL24239-SL24239-OEB1354.html?refid=FR49-OEB1354

 

B

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It's not really the price I'm concerned about. If it costs $10, then it cost $10, but if $100 is what it takes to do it properly, then so be it.

I only mentioned that the gallon of Napa fluid is $36 for reference. $36 for a gallon (4quarts) is a little on the low side, isn't it?

I want to get something of decent quality so I don't uselessly waste $36.

I don't want to buy 5qt. of the Napa fluid for $50, then find out that my trans won't shift for @!*% and then I have to put out another $100 for Redline.

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Isn't the transmission's fluid capacity 5.1L according to the TSB, which equals 5.389 quarts? So you'd need to buy 6 quarts of your desired fluid. I'm assuming you have a 4WD, I don't remember exactly what you have.

 

Ask for the MSDS for the NAPA fluid so I can find out who makes it, or post the part number or link to the fluid so I can do some research.

Edited by Towncivilian
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Isn't the transmission's fluid capacity 5.1L according to the TSB, which equals 5.389 quarts? So you'd need to buy 6 quarts of your desired fluid. I'm assuming you have a 4WD, I don't remember exactly what you have.

 

Ask for the MSDS for the NAPA fluid so I can find out who makes it, or post the part number or link to the fluid so I can do some research.

Alright. So yeah I guess I do have to buy 6 quarts.

Ask for the MSDS? What is that so I sound like I at least have a hint of what I'm talking about.

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material safety data sheet

duh..I should have known that.

 

Any chance you can find the oil listed online @ napaonline.com?

I can't figure Napa's website out at all. That thing is all jumbled up. Whenever I get into the oil or lubrication sections, it keeps organizing them by states? It lists random states and Maryland isn't there.

I looked for gear oil, and all I could find was tractor oil or something?

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