* GL4 vs. GL5 GEAR OIL *

Dealing with all subsystems specific to the diesel powered Datsun-Nissan 720 pickup trucks.

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moose60
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* GL4 vs. GL5 GEAR OIL *

#1

Post by moose60 » 13 years ago

Hello all,
I am wondering about the differences in gear oil ratings. Why does my datsun manual specify GL4 oil for the trans, and GL5 for the differential? Will using GL5 in both hurt anything? I saw another posting on this site that mentioned somthing about syncros and GL4 compatability, but it wasn't clear to me.
Thanks.

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asavage
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#2

Post by asavage » 13 years ago

Theory says that the higher concentration of EP additive(s) that are needed to meet the GL-5 spec may promote a corrosion rate that is higher than a lubricant that barely meets the GL-4 spec. That's theory, anyway.

In practice, the front two bearings in your FS5W71 gearbox are going to die long before the niggling difference between GL-4 and GL-5 add up to a smattering of difference in the bronze/brass-based parts. [edit: I have changed my mind on this. See further downthread.]

Those of us who have a rather intimate knowledge of the FS5W71x transmission use and recommend a synthetic-based gear lubricant. Which brand and of what spec is debateable, but any synthetic gear lube of any viscosity range is going to be much superiour to the alternative.

Redline (MTL) and AMSOil (75W90 Severe Gear, $11/qt.; , 75W140 Severe Gear, $14/qt.; 80W90 Std Synth, $8/qt. ) make synthetic gear lubes that are the most mentioned. AMSOil even has a synth manual transmission lube specifically for GL-4 transmissions (75W90, $10/qt.) if that's a concern. But I don't let it keep me up at night.

Royal Purple and Lucas also have well-regarded synthetic gear lubes in various grades.

Valvoline has a synthetic gear oil that is stocked in many auto parts stores. I've used it in diffs, it seems to hold up OK.

Be warned, it's not cheap. Expect to pay $8-22 per quart for synthetic gear lube.

I hope this helps or at least partially answers your query.
Last edited by asavage 12 years ago, edited 1 time in total.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

moose60
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Location: Seattle WA

#3

Post by moose60 » 13 years ago

Thank you for the response, I suspected that this was the case but wanted to make sure. I recently changed to Mobil 1 75w-90 in the trans and diff. Thanks again.

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ecomike
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#4

Post by ecomike » 12 years ago

There is some good ( I Think) info on the GL-3, GL-4 & GL-5, sulfur attack on brass synchro issue at this link:
http://www.naxja.org/forum/showthread.p ... +lubricant

I am now wondering what was used in mine after I rebuilt it. I know it got a quart of Lucas gear oil additive, but I do not know what base lube was used, as I had someone else install the tranny and fill it for me. I was getting ready to check the level and top mine off when I starting searching for what to use. So far all I can find is stuff that claims to meet all three specs at the same time, but some of the Jeep guys on the forum above say that is BS, that GL-5 can not meet GL-3 due to the GL-5 requirment for lots of sulfur and a very low limit on the GL-3 for sulfur. They also are quite convinced that GL-5 sulfur levels will eat the brass / bronze synchros in no time. One of those guys, "5-90", is somewhat of a metalurgist.

If I understand Al's comment the GL-5 EP additives, or extreme duty additives are desirable for the known to be weak bearings. But these guys at the other site have me convinced that a true GL-5's sulfur content is a real bad idea too. I am going to do some research on this and see if I find out any more facts from the lubricant companies and their chemists. If I come up with any useful answers I will add the here.

Last minute addition:

I thought I was looking for GL-3, just rechecked my FSM and GL-4 is actually recommended in my 82 Nissan FSM. Also just read the RedLine page on their MTL and MT-90, looks like I may go with their MT-90, I am impressed with what I read at:

http://www.myoilshop.com/MTL_GearTech.html

I would still avoid most products labeled GL-5, unless they are specific about what they really mean like Redline did.

I am also finding some interesting stuff on an MT-1 spec at:

http://forums.corvetteforum.com/showthread.php?t=995957

and a few more links I am stil reading but already noteworthy:

http://www.octoil.com/index2.html
Regards,

Mike

1985 Jeep Cherokee Pioneer, 2WD, retrofitted with SD-22 & 5 spd manual trans, a 4X4 Gas Wagoneer ltd. (XJ) Jeep, 4.0 L w/ AW4 auto, and now 2 spare 2wd Jeeps, 87 & 89.

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asavage
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#5

Post by asavage » 12 years ago

Over time, I have changed my position on recommendation for the trans, to non-GL-5. While I still do not think it is as large an issue as the Jeep folks do (because I run exclusively synthetic base stock lubricants), better is better, and AMSOil's MTG 75W-90 API GL-4 and Redline's MTL 75W/80W GL-4 and MT-90 75W90 will be my top recommendations.

I hope Philip won't make too much of my waffling.
Regards,
Al S.

1982 Maxima diesel wagon, 2nd & 4th owner, 165k miles, rusty & burgundy/grey. Purchased 1996, SOLD 16Feb10
1983 Maxima diesel wagon, 199k miles, rusty, light yellow/light brown. SOLD 14Jul07
1981 720 SD22 (scrapped 04Sep07)
1983 Sentra CD17, 255k, bought 06Jul08, gave it away 22Jun10.

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ecomike
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Location: Houston Tx

#6

Post by ecomike » 12 years ago

asavage wrote:Over time, I have changed my position on recommendation for the trans, to non-GL-5. While I still do not think it is as large an issue as the Jeep folks do (because I run exclusively synthetic base stock lubricants), better is better, and AMSOil's MTG 75W-90 API GL-4 and Redline's MTL 75W/80W GL-4 and MT-90 75W90 will be my top recommendations.

I hope Philip won't make too much of my waffling.
Philip is probably bored and looking for something to do anyway, so waffle away, LOL.

I have not taken a look at the Amsoil products you mentioned, but I had made up my mind to order and try redline's MT-90 after nearly a day of driving around searching locally and searching the internet and finding nothing but MT-90 that I was willing to use. Glad to see that my choice is one of the ones on your list. I am going with MT-90 versus the MTL due the hot climate here in Houston. I may take one last look at Amsoil before I order.
Regards,

Mike

1985 Jeep Cherokee Pioneer, 2WD, retrofitted with SD-22 & 5 spd manual trans, a 4X4 Gas Wagoneer ltd. (XJ) Jeep, 4.0 L w/ AW4 auto, and now 2 spare 2wd Jeeps, 87 & 89.

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ecomike
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Location: Houston Tx

#7

Post by ecomike » 12 years ago

Well the deed is done. I am now running MT-90 in her.

I could have made a very nice dark brown metallic flake bronze paint out what I drained out of there yesterday. It was a mix of 2 brands of GL-5 in there for less that 8,000 miles. There was definately something bad going on in there with the GL-5 and the brass.

I think I got to it soon enough. Not enough total bronze/brass to have caused any serious damage yet. Almost lucky I had the problem with the shifter last month or I might not have discovered the GL-5 error I made until it was too late. Perhaps these gremlins helped me out this time, LOL.

The synchros were brand new so they should still outlast those main input bearings.
Regards,

Mike

1985 Jeep Cherokee Pioneer, 2WD, retrofitted with SD-22 & 5 spd manual trans, a 4X4 Gas Wagoneer ltd. (XJ) Jeep, 4.0 L w/ AW4 auto, and now 2 spare 2wd Jeeps, 87 & 89.

weezledeezle
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Location: Crestone, CO

Trans Fluids...

#8

Post by weezledeezle » 12 years ago

I had an idea a few years ago that has paid off very well for me. In front and rear diffs, the trans, and TC, I started with a tube of engine assembly lube (yay molybdenum disulfide) and 0w-20 synthetic engine oil (Mobil1) then topped off with M1 synthetic 75w-90 gear lube- very runny, very slippery, very smooth. Lube has no noticable change in 30k miles, and shifts are smooth and fast, as well as 2 mpg better mileage, and trans runs about 25-30 degrees F cooler. Worked great for me. As far as I am concerned no-one bottles a good gear lube- why I made my own.
84 Jeep XJ Wagoneer 4wd w/ Nissan SD22 and TC-05 turbo w/ 2-1/2" straight pipes to a BW T5 trans. Mods and Mods and Mods everywhere. 40 mpg avg and climbing.

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philip
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Location: Southern California, USA

Re: Trans Fluids...

#9

Post by philip » 12 years ago

weezledeezle wrote:SNIP- ...as well as 2 mpg better mileage, and trans runs about 25-30 degrees F cooler.
Tell me about the thermocouple and gauge in your transmission.
weezledeezle wrote:SNIP- As far as I am concerned no-one bottles a good gear lube- why I made my own.
You're on your own. I'll stay with API/SAE and Nissan's recommend of GL3 and GL4 in these old synchronized transmissions.

Oh yeah, :wink: Al too.
-Philip
Passed 08May2008
My friend, you are missed . . .

1982 Datsun 720KC SD-22

"Im slow and I'm ahead of you"

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asavage
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#10

Post by asavage » 12 years ago

I don't think I'd try moly in a transmission.

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