Gearbox oil additives/friction modifiers

[Jake Royd]

I have an x250, the gearbox was replaced with a recon unit 2 years ago.
Generally it's ok but sometimes the upshift from 3rd to 4th is crunchy, indicating weak synchromesh.
Downchanges into 4th perplexingly are ok.
I assume the oil level is ok but have not checked it yet.

I know , if I understand correctly that synchromesh on 4th and 5th is weak on these gearboxes anyway.

I am an ex automotive transmissions engineer so I know how synchromesh works.

My question is have any Funsters had similar issues and have used an oil additives or modifier. Did it improve things and which one and what dose did you use?

TIA

 

[tonyidle]

I have used Molyslip in everything I've owned.

 

[Landy Andy]

Molyslip and fully synthetic oil in my 250 box now

 

[Two on Tour]

I changed the gearbox oil in our X250 to Castrol Syntrans Multivehicle 75W-90 fully synthetic and added 10% of Activ8 friction reducer and the gear change is as smooth as silk now.

 

[PeteH]

There appears to be no reason why Oil Treatment additives cannot be used, But some are formulated allegedly just to be used with low viscosity synthetic lubricants. So I guess it`s read the label?.

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[Jake Royd]

Thanks for your replies.
I shall look into your recommendations.

 

[bigwood]

Modern gearboxes should not need any additives if designed and built properly. I have driven large vehicles with crash gearboxes filled with normal gearbox oil. The only reason for problems with gear changes were down to bad drivers rushing the changes.

 

[Two on Tour]

Everyone just loves an expert.

 

[tonyidle]

Molybdenum disulphide is added to lubricants operating under extreme pressure. In the automotive world it's found in CV joints. It's a expensive substance therefore only used when essential. I have never seen wear where it has been added. In the case of some Fiat / Peugeot van gearboxes with the after-thought fifth gear arrangement it could possibly be useful insurance against lubrication failure.

 

[Jake Royd]

Modern gearboxes should not need any additives if designed and built properly. I have driven large vehicles with crash gearboxes filled with normal gearbox oil. The only reason for problems with gear changes were down to bad drivers rushing the changes.

You may be correct but remembering I have a recon gearbox, there are some things to consider.

When a gear is selected the synchro sleeve slides on the hub with its tooth form engaging the teeth on the synchro ring. The cone on the ring then acts like a little clutch matching the speed of the bits concerned.
Once done this allows the sleeve to continue to slide and engage the new gear.
However, there is a slot in the system that allows the ring to turn momentarily as the clutch action takes place.
Synchronization is a function of the inertia involved, the lubricant, cone angle, cone surface and also the speed you shift at.

Most gearboxes will have a gap between the ring and the gear allowing a measure of the wear limit on the system.

I can be things like this a rebuild does not always get right.

As you can see from the description above an additive modified cone friction, thus changing one of the system variables.

Hence my interest in the experience of others.
Thank you once again.

Many gearboxes these days have double or triple cones on 1st and 2nd.

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[Landy Andy]

Italian engineering.

So it needs all the help you can give it

 

[Clipgate]

Interesting observation regarding European engineering, who would consider Spain as the epitome of Quality engineering,
Licences for Hispano-Suiza patents were much in demand from prestige car manufacturers world-wide. Rolls-Royce used a number of Hispano-Suiza patents. For instance, for many years Rolls Royce installed Hispano-Suiza designed power brakes in its vehicles.

 

[IslandApe]

Interesting observation regarding European engineering, who would consider Spain as the epitome of Quality engineering,
Licences for Hispano-Suiza patents were much in demand from prestige car manufacturers world-wide. Rolls-Royce used a number of Hispano-Suiza patents. For instance, for many years Rolls Royce installed Hispano-Suiza designed power brakes in its vehicles.

To be fair, that organisation's founding partnership was half Swiss , hence the name. After the outbreak of the Spanish Civil War they collectivised their factories which was the end of a proud engineering concern.

As usual, nationalisation buggers it up except for bureaucrats...

 

[Jake Royd]

Has anybody found an additive that specifically improved the synchromesh performance, rather than reducing friction?
My 4th gear only crunches slightly when the oil is hot and also only on upchanges. This is interesting as usually syncros are less able to perform on downchanges.

So something that perhaps makes the oil more visous at high temperatures might work?

 

[Two on Tour]

Has anybody found an additive that specifically improved the synchromesh performance, rather than reducing friction?
My 4th gear only crunches slightly when the oil is hot and also only on upchanges. This is interesting as usually syncros are less able to perform on downchanges.

So something that perhaps makes the oil more visous at high temperatures might work?

Change your gearbox oil for a different viscosity, maybe a 75W- 110 or a 75W-140 rather than the 75W-90

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[Jake Royd]

Change your gearbox oil for a different viscosity, maybe a 75W- 110 or a 75W-140 rather than the 75W-90

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Has anybody done this and had a good outcome?

 

[tonyidle]

You cannot modify synchro friction performance by changing the oil grade. Use a modern synthetic and add Molyslip.

 

[Two on Tour]

You cannot modify synchro friction performance by changing the oil grade.

What evidence do you have to back that statement up ?

 

[Jake Royd]

Thanks both.
I am just using the logic that a cold more viscous oil at start up seems to be ok for the gearchange.
The thicker oil , i assume, changes the timing element of the change as in my description above.
If I change into 4th slowly and at modest revs(relatively) it's ok.

 

[PeteH]

i remember when the likes of moly first came out there was a lot of chatter about wether or not it was going to reduce the small amount of friction necessary for the syncros to work properly?.

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[Jake Royd]

i remember when the likes of moly first came out there was a lot of chatter about wether or not it was going to reduce the small amount of friction necessary for the syncros to work properly?.

Yes, I’ve wondered the same.
Moly might make the synchros worse.

 

[Geo]

Thought about using ATF in your manual box ?

 

[tonyidle]

Synchro failures were at their worst when the norm was to use SAE 80+ gear oils. By comparison modern gear oils are like water. I have used Molyslip in every gearbox I've ever had including auto and o/d boxes and in PAS. It invariably results in an improvement in "feel" and a smoother unit.

 

[Jake Royd]

I have looked on the top of my gearbox, it has the black plastic breather which I propose to use to check the oil level in the gearbox.
Although I know you are supposed to put the correct quantity of oil in and leave it for life.

Can anybody advise if the oil level is dippable via the breather and if so about at what level a temporary dipstick through the hole would show?
TIA

Curiously , it has changed into 4th fine for the last few trips , although I am taking the change up very easy. Makes me wonder about debris in the box (it is a recon after all)

 

[Steviechi]

After 130k miles and a crunchy gearbox into 2nd and 3rd, I replaced transmission fluid with Red-Line.
Put in the required qty and gearchange is smooth now.

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[Steviechi]

I have looked on the top of my gearbox, it has the black plastic breather which I propose to use to check the oil level in the gearbox.
Although I know you are supposed to put the correct quantity of oil in and leave it for life.

Can anybody advise if the oil level is dippable via the breather and if so about at what level a temporary dipstick through the hole would show?
TIA

Curiously , it has changed into 4th fine for the last few trips , although I am taking the change up very easy. Makes me wonder about debris in the box (it is a recon after all)

Jake - no it's put in the correct quantity and leave for 100k miles

 

[Jake Royd]

Jake - no it's put in the correct quantity and leave for 100k miles

I know but was also wondering if there is an additional level check that could be done.

 

[Jake Royd]

For me, I would not put ATF in a manual gearbox.
Forgive me if that is not what you meant.

 

[tacr2man]

RED Line Synthetic , and no other additives . I have fitted gearboxes in Australia , and also seen test results of usage in Road trains , its not cheap tho !

 

[Otter Spotter]

Modern gearboxes should not need any additives if designed and built properly. I have driven large vehicles with crash gearboxes filled with normal gearbox oil. The only reason for problems with gear changes were down to bad drivers rushing the changes.

I think the OP,s point is he knows that the gearbox has design faults hence wanting to reduce issues with additives

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