1800: Recommend Modern oil for M41 gearbox, UK climate?

[142 Guy]

Originally Posted by simonvolvo

Those cans had many uses. Back in the days, I turned one of them into a guitar.

https://www.youtube.com/watch?v=bXtNDQZdw0s

Can’t do that with a plastic one.

My oil can experience was all 1 qt round cans so I initially had some conceptual problems with an oil can guitar. I don't think 4 qt tins of oil were common or even available in North America. All the Castrol I purchased came in 1 qt tins - including Castrol R, the real castor oil. The 4 qt tin having a screw top would get around my primary objection to the 1 qt can.

Nice U tube of a can guitar with a genuine Castrol can.
https://www.youtube.com/watch?v=ZZf5F7IbbBU
With anything close to conventional string tensions / tuning I don't know how he stops the can from folding in half. Not having a sound hole helps; but, I am suspicious that there might be a little re enforcement added inside the guitar.

[142 Guy]

Originally Posted by simonvolvo

Those cans had many uses. Back in the days, I turned one of them into a guitar.

https://www.youtube.com/watch?v=bXtNDQZdw0s

Can’t do that with a plastic one.

I was initially having a little trouble with guitar and 1 qt round can! A 4 qt tin solves that and with a screw on lid would address my objection to the 1 qt tin. Nice U tube with a genuine vintage Castrol GTX oil can.

https://www.youtube.com/watch?v=ZZf5F7IbbBU

Do they still sell oil in 4 qt tins in GB?

[ChasesDragons]

I am back again!! I want some clarification on the use of synthetic oils in the overdrive gearboxes - some technical background pls.

I thought I will carry on this thread than create a new one.

Basically, 20w50 Mineral oil is mentioned for these gearboxes. Is there a technical reason why would we not use synthetic?

I have motorbikes running wet clutches. We would use synthetic motorcycle oil which bathes the engine and clutch. Meaning that it doesn't have slip additives that will cause clutch slip (M41 Overdrive), the motorcycle oils also have an additive or structure to reduce the shearing of the oil chains as they are ground through the gear teeth which thins it quickly.....soo.....I am thinking of using a synthetic 20W50 Motorcycle oil. I can get Mineral 20w50 MC oil too, but synthetics have other positives too?

I don't want to gondown the Redline MTL path now - it is expensive and my gearbox is working absolutely fine at thisntime.

Warmest Regards
U

[Othen]

Originally Posted by ChasesDragons

I am back again!! I want some clarification on the use of synthetic oils in the overdrive gearboxes - some technical background pls.

I thought I will carry on this thread than create a new one.

Basically, 20w50 Mineral oil is mentioned for these gearboxes. Is there a technical reason why would we not use synthetic?

I have motorbikes running wet clutches. We would use synthetic motorcycle oil which bathes the engine and clutch. Meaning that it doesn't have slip additives that will cause clutch slip (M41 Overdrive), the motorcycle oils also have an additive or structure to reduce the shearing of the oil chains as they are ground through the gear teeth which thins it quickly.....soo.....I am thinking of using a synthetic 20W50 Motorcycle oil. I can get Mineral 20w50 MC oil too, but synthetics have other positives too?

I don't want to gondown the Redline MTL path now - it is expensive and my gearbox is working absolutely fine at thisntime.

Warmest Regards
U

The specified oil (in the green book) is 'SAE 20W40 Engine Oil', it doesn't say anything about mineral or synthetic oil because that would have been irrelevant in 1960. The implication is that mineral oil would be fine. I suspect synthetic oil would be just as fine as the gearbox doesn't get very hot, it doesn't contain reciprocating parts and the oil never comes into contact with the products of combustion.

I would wonder why one would change to synthetic oil though? It is more expensive and 20W50 mineral oil works just fine. I can't think of any advantages synthetic 20W50 oil would have, and you would pay more for a tin with a picture of a motorcycle on it (I'm a biker, one always pays more for motorcycle specific stuff - what bunkum).

If it ain't broke, don't fix it.

Alan

[Burdekin]

Originally Posted by ChasesDragons

I am back again!! I want some clarification on the use of synthetic oils in the overdrive gearboxes - some technical background pls.

I thought I will carry on this thread than create a new one.

Basically, 20w50 Mineral oil is mentioned for these gearboxes. Is there a technical reason why would we not use synthetic?

I have motorbikes running wet clutches. We would use synthetic motorcycle oil which bathes the engine and clutch. Meaning that it doesn't have slip additives that will cause clutch slip (M41 Overdrive), the motorcycle oils also have an additive or structure to reduce the shearing of the oil chains as they are ground through the gear teeth which thins it quickly.....soo.....I am thinking of using a synthetic 20W50 Motorcycle oil. I can get Mineral 20w50 MC oil too, but synthetics have other positives too?

I don't want to gondown the Redline MTL path now - it is expensive and my gearbox is working absolutely fine at thisntime.

Warmest Regards
U

Be worth contacting one of the OD specialists and ask them.

[Derek UK]

This is a regular question. No need to reinvent the wheel. Use a good quality 20/50 mineral oil (not synthetic) in both the engine and gearbox (M40 or M41).
If you have no leaks you could indeed consider MTL for the gearbox. With, say, 50k mile changes, the small extra expense becomes irrelevant.

[142 Guy]

The Red Line MTL is a synthetic base stock. Its primary claim to fame are the friction modifiers that improve operation of the synchros. As a side note, Red Line is not the only SAE gear oil for use with manual transmissions. GM sells a product called Synchromesh Modified which has similar properties. I have been using Red Line MTL in cranky Volvo gear boxes since 1995 without issue.

As a perhaps obvious side note, you would never use Red Line MTL in a motorcycle with a multi disk wet clutch. The friction modifiers would turn the clutch into a miserable grabby affair.

If you don't need the friction modifiers in a specialty transmission oil, then just go with an engine oil that complies with the viscosity recommendations in the Volvo owners manual. An oil with either a synthetic or conventional base stock will work just fine. The absence of combustion by products and not having to lubricate cylinder walls makes a lot of the benefits of synthetic base stock moot. However, these days, it may be easier to find a synthetic in the viscosity you want.

If your M41 is all original, there 'may' be an upside to sticking with a conventional base stock oil. Some seals and gaskets have a problem with some synthetic base stocks. The seals and gaskets swell upon exposure to conventional base stock and may 'un-swell' upon exposure to synthetics leading to oil leaks. Modern synthetics are supposed to have addressed that un swell problem; but, sticking with a conventional base stock should eliminate that uncertainty.

I would not seek out a motorcycle specific oil for the Volvo unless you like to spend more money on your oils. I had a 1980 Honda CB 750F which I owned for 25 years and it ran just fine on various versions of non MC labeled Castrol Syntec or Mobil 1 xxW50 or 10W40. The engine continued to run just fine for the second owner until they wadded the rest of the bike up in a fit of over enthusiasm.

[ChasesDragons]

Right as a matter of closure and thank you; I managed to do the gearbox oil change after weeks of procrastination.

Did a 35 mile motorway run, parked it, jacked it up and took both square drives off to drain it without getting airlock. Barbequed myself on the hot exhaust, in the process. I jacked the vehicle at the rear left to see if more of the oil from the OverDrive would come out - I just could not bring myself to do it properly as recommended (filter clean).

The oil was really mottled grey brown and hot. There was a lot of material on the magnetic drain plug - see pic.

Refilled with LIQUI MOLY OIL 4 STROKE - MINERAL - 20W-50 motorcycle oil. Used a funnel and a length of garden hose to fill the box from the engine bay - whoever showed me this trick, THANK YOU!

Took it for a good drive and I think I can feel a difference in how well the gear changes go. Over drive is also functional.

Thank you again for your knowledge 👍🏼

[Derek UK]

Motorbike 4T 20W-50 Street?
If this oil contains ANY molybdenum sulphide it is not suitable for the M41. The moly will make the clutches slip. Some of Liqui-Moly's oils contain moly and some don't. If it does have moly in it you will have great difficulty getting it out as it coats the internals. May have to be stripped and cleaned before rebuilding.

[ChasesDragons]

Motorbike oils tend not to have friction modifiers as they tend to run wet clutches. A lot of MC specific oils also have compounds to promote stability as the oil molecules (longnchains) can be cut to shreds by the gearing.

At least this is what I learnt and l8ved by when I used motorcycles, and this is what I used to rationalise buying this oil. No issues yet after another 80 miles of thrashing.