Oil gurus. advice please on 164 diff oil replacement

[Nextmove]

Oh wondrous beings who have the necessary IQ ratings to decipher the gobbledygook of oil classifications and can shed some cooling insights on the fevered (no, not corona infected....yet) brain of somebody trying to make some sense about what I thought was a simple job (... till I tried reading up about it)... Assistance requested.

My 71 auto 164 is in the process of being progressively drained of it's ancient life fluids and transfused with new and healthy (I hope) vitality and long life.

Done the coolant. No prob. Just Volvo coolant 50/50 solution. Probably need a few more changes though. It's still a bit grungy looking, despite the garden hose giving the system a colonic irrigation several times.

I've already asked on here about engine oil and decided to go 15/40. Oil is on the shelf, just need some decent weather to get it done.

Got Kroons ATF type F in the mail for the transmission (as specified in manuals), and think I should get away with using this also for the PS, though if somebody shouts NO!! at me, I'll get some ATF type A (as specified) instead.

Diff oil specification is SAE90, MIL - L - 2105B. Or SAE 80 if extremely cold, which it isn't, even in Scotland. The MIL etc code seems to translate as either GL4 or GL5 rating, and that then brings up the question of whether GL5 is better than GL4 or will it eat seals and other items in a 49 year old diff? I've been getting apparently contradictory or just plain confusing info for hours now in Encyclopaedia Google and have torn my few hair remnants out in disbelief. Doesn't anybody agree with anybody else?

Kroons have both GL5 and GL4 versions of SAE 90, but not enough product description to make a choice. My suspicion is that the GL4 grade is better suited to older diffs/gearboxes, and I should go for 5. I don't want to use anything fancy including things more suited to LSDs in case it does something nasty in the process.

All this fuss when probably any old SAE80/90 might be perfectly alright for the job is simply down to fears of wrecking something very expense, even if it happens slowly.

I know that modern oils are generally much better than old ones, and I should move with the march of progress, but as I said in a previous post, I needed a moderately expensive steering rack replacement in a 92 BMW 3 series a few years ago because the previous owner's servicing mech had used the wrong ATF, which ate the rack seals.

Comments appreciated (in words of few syllables that I can follow, please).

Many thanks,

Lee

[dingov70]

Morning

The main difference between GL-4 and GL-5 gear oils is how much extreme-pressure additive has been included in the mix. GL-5 oil has roughly twice as much of the EP additive as GL-4.

Gear oils all include some level of sulphur or phosphorous additive. This additive coats the gears and wears off as they rub against each other. This process protects the gears from wear. GL-4 is typically used for vehicles with a high level of yellow metal, because the additive corrodes such metals.

The American Petroleum Institute sets the guidelines for automotive gear lubricants according to their intended use. The API category GL-4 for gear oils designates the lubricant as appropriate for spiral-bevel and hypoid gears in automotive axles. The car should be operated under moderate speeds and loads. GL-4 oils are appropriate for selected manual transmission and trans-axle applications.

I have moved over to 75w//90 EP oils based on fully synthetic stock with no problems what so ever . It just saves having multiple drums of oil when one does most of what i require . A gl4 based oil will be more than good enough for your needs , remember it is designed to work using old oil technology & therefore the fact you are replacing the old with newer better lubricant can only be a good thing .

New oil is good oil as additive packs disintegrate with heat / pressure / age / shearing effects of gears

[Burdekin]

I’ve used this Smith and Allen for old machinery oil specs and they supplied me with the correct modern equivalent. If you know what the manual says they will be able to tell you what you need.

[Clan]

Originally Posted by Nextmove

Oh wondrous beings who have the necessary IQ ratings to decipher the gobbledygook of oil classifications and can shed some cooling insights on the fevered (no, not corona infected....yet) brain of somebody trying to make some sense about what I thought was a simple job (... till I tried reading up about it)... Assistance requested.

My 71 auto 164 is in the process of being progressively drained of it's ancient life fluids and transfused with new and healthy (I hope) vitality and long life.

Done the coolant. No prob. Just Volvo coolant 50/50 solution. Probably need a few more changes though. It's still a bit grungy looking, despite the garden hose giving the system a colonic irrigation several times.

I've already asked on here about engine oil and decided to go 15/40. Oil is on the shelf, just need some decent weather to get it done.

Got Kroons ATF type F in the mail for the transmission (as specified in manuals), and think I should get away with using this also for the PS, though if somebody shouts NO!! at me, I'll get some ATF type A (as specified) instead.

Diff oil specification is SAE90, MIL - L - 2105B. Or SAE 80 if extremely cold, which it isn't, even in Scotland. The MIL etc code seems to translate as either GL4 or GL5 rating, and that then brings up the question of whether GL5 is better than GL4 or will it eat seals and other items in a 49 year old diff? I've been getting apparently contradictory or just plain confusing info for hours now in Encyclopaedia Google and have torn my few hair remnants out in disbelief. Doesn't anybody agree with anybody else?

Kroons have both GL5 and GL4 versions of SAE 90, but not enough product description to make a choice. My suspicion is that the GL4 grade is better suited to older diffs/gearboxes, and I should go for 5. I don't want to use anything fancy including things more suited to LSDs in case it does something nasty in the process.

All this fuss when probably any old SAE80/90 might be perfectly alright for the job is simply down to fears of wrecking something very expense, even if it happens slowly.

I know that modern oils are generally much better than old ones, and I should move with the march of progress, but as I said in a previous post, I needed a moderately expensive steering rack replacement in a 92 BMW 3 series a few years ago because the previous owner's servicing mech had used the wrong ATF, which ate the rack seals.

Comments appreciated (in words of few syllables that I can follow, please).

Many thanks,

Lee

This is ideal for all hypoid final drives ( except limited slip which a few 940's have )

synthetic , low friction and long long lasting proved by me in many vehicles rear axles over 100,s of 1000's of miles since 1989

https://www.ebay.co.uk/itm/Castrol-S...8AAOSwYOxeOuLn

[37 RUBY]

Originally Posted by dingov70

Morning

The main difference between GL-4 and GL-5 gear oils is how much extreme-pressure additive has been included in the mix. GL-5 oil has roughly twice as much of the EP additive as GL-4.

Gear oils all include some level of sulphur or phosphorous additive. This additive coats the gears and wears off as they rub against each other. This process protects the gears from wear. GL-4 is typically used for vehicles with a high level of yellow metal, because the additive corrodes such metals.

New oil is good oil as additive packs disintegrate with heat / pressure / age / shearing effects of gears

Good to see this element being addressed especially when the topic is an older vehicle. Car too many times people are witnessed saying it can only be a good thing to substitute with newer graded oils.

Certain extreme pressure additives chemically react with these softer yellow metals, causing premature wear and even failure.

To the OP, my only suggestion would be to research whether or not your transmission contains any phosphorus bronze/yellow metal components.

[Nextmove]

Thanks to all for your comments.

I think the nett result for my thinking so far is that I'll go with an older style oil as specified by Volvo, and do at least yearly (but probably more often) changes, since it doesn't involve much oil (for the diff at least). I will be doing only low miles and pretty sedate driving.

I'll be doing the same for engine oil (every 6 months), transmission and PAS oil (multiple part changes at first, then at least yearly), and coolant (yearly) anyway, so even if my choice of medicine isn't the best available, I'll be renewing it far more often than the books specify, and hopefully not running the risk of modern recipe ingredients doing unpleasant things.

Being just a tad overcautious perhaps, but the car seems to be a very good one apart from minor age related things (so far), and I want it to outlast me.

And hopefully, in the present health climate, that means a bit longer than next week..... Best wishes to all out there, and if you do have anyone close to you who is working and putting themselves at risk on a front line, of any kind, anywhere, please pin an extra medal on them for me when things settle down a bit. They're amazing.

I'll do some homework, 37 Ruby, to try to find out if I have any potential trouble spots re metals in my diff. Brain fry prevented this before.

I'm now trying to get some advice from Frosts re best of 3 possible choices of SAE 90 Kroon, and Millers, Classic gear oils, and also from Smith and Allen, as recommended by Khe Sanh. At present both places seem to be overwhelmed with people asking for phone advice and there's a wait to get to the resident guru, but I'm not in a desperate hurry. I'll mix this advice together with what people have said here, and my own reading, and see what rises to the top. Thanks again to all.

And in the meantime I've found my local garage man, who I thought had shut down, but was getting by on MOTs (which have apparently all just been cancelled till October by government decree), and who likes old Volvos, is happy to let me put the car up on his hoist and have a damned good look underneath for hidden gremlins (weather and lack of space have so far made this difficult beyond a quick squizz).

AND I may be able to get him to do a full brake flush for me, as long as I drop the car off and keep well away from him while that happens.

I now refuse to do brake flushes if I can help it. It always ends with tears and a godawful mess when I've tried doing it single handedly in recent years, even when I had an expensive foolproof gizmo at hand. It worked fine on my motorbikes, but I never got it right on cars and had to go back to the good old assistant-on-the brake-pedal-down-hold-up-technique.

For which you need a patient assistant who understands what you want them to do, and listens to you........ I'll say no more........

[BrendanHurley]

I changed the differential oii in my '72 144 last year and used Liqui Moly 1404 GL 5 SAE 85 W-90 Hypoid Gear Oil (amazon link below) which I think was compatible.

However, since i changed the oil it feels like there is a slight whine/hum from the rear at 40mph that wasnt noticeable before... of course I could be imagining it as Im always listening to every squeak and rattle as there are very few on this car.



https://www.amazon.co.uk/Liqui-Moly-...WMDMP9XQSPP93A

[Clan]

Originally Posted by BrendanHurley

I changed the differential oii in my '72 144 last year and used Liqui Moly 1404 GL 5 SAE 85 W-90 Hypoid Gear Oil (amazon link below) which I think was compatible.

However, since i changed the oil it feels like there is a slight whine/hum from the rear at 40mph that wasnt noticeable before... of course I could be imagining it as Im always listening to every squeak and rattle as there are very few on this car.



https://www.amazon.co.uk/Liqui-Moly-...WMDMP9XQSPP93A

Have you got an overdrive?

[BrendanHurley]

No overdrive, its a auto box, BW35.

[BrendanHurley]

Originally Posted by Clan

Have you got an overdrive?

No overdrive, its a auto box, BW35.