Transmission oil

Lawson Cox said:
That's taking a leak, isn't it?

There are no "seals" in the area he is speaking of.
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Right you are. I think it's leaking were the gear shafts slide thru the case.

Guy before more just put a shmear of rtv over the visible ends of the shafts. Not to pretty but doesn't seem to leak.
 
I always heard that GL4 was safe to use and that GL5 would eat yellow metal.
In our life time GL 5 will stain the yellow metal but not eat it up. Is causes it to turn grey.
If you throw salt over your left shoulder you’ll be ok.
 
Aarongriffey said:
I always heard that GL4 was safe to use and that GL5 would eat yellow metal.
In our life time GL 5 will stain the yellow metal but not eat it up. Is causes it to turn grey.
If you throw salt over your left shoulder you’ll be ok.
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I don´t know how many gearboxes i have changed syncros in where the owner in good faith bought the most expensive gearoil he could find.
It takes a very short period to turn the oil into a nice brass colour.
Do you know how EP additives work??
It´s not a nice little magic cushion that goes in between...it etches into the metal forming a wear barrier of oxide.
Even if GL4 doesn´t eat away on brass they reduce the friction in the synchros which isn´t desired.
A gearbox isn´t a hypoid gear like a rearaxle and load is very mild in comparsion.
 
One guy was telling me one week of driving with GL5 was enough to kill the synchros totally in his car
 
flatheadmurre said:
I don´t know how many gearboxes i have changed syncros in where the owner in good faith bought the most expensive gearoil he could find.
It takes a very short period to turn the oil into a nice brass colour.
Do you know how EP additives work??
It´s not a nice little magic cushion that goes in between...it etches into the metal forming a wear barrier of oxide.
Even if GL4 doesn´t eat away on brass they reduce the friction in the synchros which isn´t desired.
A gearbox isn´t a hypoid gear like a rearaxle and load is very mild in comparsion.
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Yet Ford recommended Mild EP gear oil?
 
So what was a mild EP additive in 1950 ?
We have to realise that around 1950 EP additives turned from leadbased to zincbased.
And the EP development really took off around 1960 and up.
GL3 is still considered mild to moderate while GL4 is heavy gearbox and moderate rear axle.
I´m not going into another oilbattle we had our share of them already...
If the product is well designed it may work just fine being a higher GL rating...if it´s needed in our mildly loaded gearboxes...my opinion is it´s not.
Any EP additive bonds up with the metal reducing friction by adding a coating in my opinion this doesn´t do us any good in the friction between syncro and cone.
A hypoid oil with a higher rating is really first needed when you have a gear that is off center like in a rear axle.
 
Not a war, just never heard of an issue with GL4 with yellow metal and most of the transmission rebuilders recommend it. I like T5z transmissions, ATF is not an issue! :)
 
JSeery said:
Not a war, just never heard of an issue with GL4 with yellow metal and most of the transmission rebuilders recommend it. I like T5z transmissions, ATF is not an issue! :)
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In Canada GL4 is becoming a thing of the past as any I've been able to find say they meet and exceed GL5 ratings. Basically it is GL5 with a GL4 sticker.

If you run 140w mineral oil in the trans and cornhead grease in the clam, in theory as there is minor mixing back and forth between the 2(without a sealed rear trans bearing) a small amount of the EP additives from the cornhead grease will mix in with the mineral oil making it a GL3?? Maybe not, just a thought...

The easiest to come by here is Lucas GL4 which when speaking to their reps, they say it is not safe and will eat yellow metals. I use chevron SAE 140 GL1 which is ISO 460. It had 600W in it when I got it and is much happier now.
 
OldDad said:
I put 600W in my 40 box and found it leaked just as well as 90. 600W is apparently similar in viscosity to modern 140, from what I've read. I think the only real solution is the o-ring seal approach for the shafts. Or just plan ahead and put a drip pan under it. As someone pointed out on here or the HAMB, those old concrete driveways with the two strips for the wheels and grass or gravel down the center made a lot of sense back in those days!
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I have thought that same thing about those.
 
just to add my 2cents worth in my 50 cpe with o.d. i use 80-90 gear oil mixed 50/50with lucas engine oil addictive i’ve had that in there 20 plus years and only have minor drips after a long trip i’ve always told my customers with older vehicles you can live with drips but not puddles and even if it’s professionally restored and you drive it its going to drip
 
I had a 5speed Aerostar. They take ATF.
One day I changed the trans oil and I put in gear oil. As soon as I stared driving I knew I had done something wrong.
It was in the summer but it shifted hard all day.
I changed it to ATF the first day and it was ok again.
I think the 600 gear tar may be too heavy to get into the bearings in the cluster gear.
 
GL-5 is supposed to be harder on bronze/yellow metals. GL-4 is supposed to be safe. GL-1 does not have the extreme pressure additives, and does not protect as well as the more modern oils.

Some oils have a GL-4/GL-5 rating, and are supposed to be safe for yellow metals as well as the latest stuff.

I have been rebuilding Ford Toploaders for 30 years, and have never had an issue with oils or yellow metals. What seems to work the best is plain, GL-4 or GL-5 NON SYNTHETIC gear oil. To be safe, choose GL-4 or one with the dual rating.

There are specialty suppliers that cater to guys with older cars. PennGrade makes a GL-4 90W non synthetic that works well in transmissions. It's only $8.99/qt. Not sure if they make heavier grades. There are reviews at the link.

https://www.summitracing.com/parts/bpo-77296
 
The thing is when you read the API spec GL-4 it today says...

3.1 API GL-4
The designation API GL-4 denotes lubricants intended for axles with spiral bevel gears operating under moderate
to severe conditions of speed and load, or axles with hypoid gears operating under moderate conditions of speed
and load. Axles equipped with limited-slip differentials have additional frictional requirements that are normally
defined by the axle manufacturer.
2 API 1560
API GL-4 oils may be used in selected manual transmission and transaxle applications where API MT-1 lubricants
are unsuitable. In all cases, the equipment manufacturer's specific lubricant quality recommendations should be
followed.
Although this service designation is still used commercially to describe lubricants, test equipment for performance
verification is not currently available. Lubricant end users are advised to request appropriate supporting
documentation on previously tested lubricants from their suppliers.

So basicly it says for rear axles use in gearbox at your own risk...

The active API MT-1 for gearboxes says for non syncronised gearboxes so that is another gamble.

Only API that actually says for gearboxes is API GL-1 and GL-3 which are non active today...but still sold.
So what i´m trying to say is that GL-4 is not safe by API rating...have to check with manufacturer of oil.
 
Jim in S.C. said:
Can you use the 600 wt. oil in a 1939 topload transmission? I am just wondering if it would cause any problems. I just want to stop some of the leaking at the back of the transmission. It is leaking around the lower of the two shafts that go in from the back end. I just don't want to tear it down to fix it. Too
icon7.gif
old and too tired!
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How much is it leaking?
 
This good timing for me. Just did a rebuild on my toploader. With all the discussion on what to use for oil, I went to the NAPA main hub and read all the labels of gear oil. The ones they had on the shelf were GL-4/GL-5 and stated "For Non-Synchronized Transmissions".
So I ask the counter guy for GL-1, who looked it up in the catalog. Sure enough they carry 90w GL-1 under heavy duty oil. It's just not on the customer shelves, you have to ask. It lists for $31.08, with a NAPA account it's only $18.99 a gallon.
 
solidaxle said:
This good timing for me. Just did a rebuild on my toploader. With all the discussion on what to use for oil, I went to the NAPA main hub and read all the labels of gear oil. The ones they had on the shelf were GL-4/GL-5 and stated "For Non-Synchronized Transmissions".
So I ask the counter guy for GL-1, who looked it up in the catalog. Sure enough they carry 90w GL-1 under heavy duty oil. It's just not on the customer shelves, you have to ask. It lists for $31.08, with a NAPA account it's only $18.99 a gallon.
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Me too. I got two gallons @ Tractor Supply for $25. I figure I'll break it in and then drain and refill.
 
That's the catch you have to watch out for on GL5 gear oil, most of them will say backwards compatible with GL4. BUT, that is referring to the lubrication properties, NOT the synchronizer compatibility. Most (if not all) GL4 gear oils should state synchronizer compatible, but anything labeled GL4/GL5 I would question. Now, some of the newer GL5s claim synchronizer compatible, which they may well be, but I would stick with GL4. GL4 has been used in synchronizer transmissions for years.
 
As was said, I've been driving and rebuilding Ford Toploaders (the cast iron ones made from 1964-to 1973-ish) for 30 years.

The places that specialize in Toploader rebuild parts/rebuild kits recommend a non-synthetic GL-4 lubricant. These transmission have brass/bronze synchros, and undergo a lot of abuse. Mine stands up to 600+ horsepower on slicks/nitrous to the tune of 9.87 1/4 miles. The GL-4 non synthetic oils are good stuff! Some will recommend 90W. Some will push for 140W. I've always used 90W Valvoline from the local parts store. Never had an issue. I've tried the GL-4 PennGrade I linked above, and it works fine as well.

I would NEVER put a crude GL-1 oil in the transmission, as it lacks the extreme pressure additives that were later developed. The non-synthetic GL-4 shifts great and I've seen zero issues with the brass/bronze synchros in the trans. Not a problem.

Good Luck
 
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