Technical Gearbox

[Baden87]

Got a problem with Ducato x250 6 speed manual gearbox grinding into 4th gear, if I do a slower gear change it’s fine any ideas guys and what’s the fix

 

[oigle]

Pretty common. Very poor synchros. A gearbox strip and fix is the obvious route but you may get a reprieve if you use auto transmission fluid in your box. Cheap fix if it works. Worth a try before spending mega bucks.

 

[Baden87]

It’s only done 28000 miles and I’m thinking of changing my motorhome so a quick cheap fix would be nice , what’s with the auto transmition fluid

 

[oigle]

The synchro rings glaze and lose their gripping ability. The auto tranny fluid seems to restore that gripping ability and allow the synchros to work properly. Has been a known fix with many different gearboxes. I first encountered it with mazda gearboxes back in the 1970's. Worked wonders.
Don't use synthetic oil - just standard auto tranny fluid, nothing fancy.

 

[Baden87]

is it any old tranny oil or a specific one

 

[Baden87]

not sure how to refill gearbox

 

[corcai]

Its all very well putting random oil into a sloppy old jalopy but yours has 28,000 on it and modern gearboxes are designed for oils with high pressure additives you could turn it to scrap and you couldnt sell it on in good faith without telling the new owner.

 

[oigle]

Never known a failure from auto fluid. After all, auto gearboxes have gears too, just like manual ones. Why would current manual gearboxes be any different from older ones? Hardly any new tech there. There are current manual gearboxes in some vehicles that stipulate auto fluid, so doubt there would be any issues. What alternative? Hundreds of pounds on a gearbox recon? If it doesn't work, what have you lost - a few quids worth of oil.

 

[corcai]

After all, auto gearboxes have gears too, just like manual ones.

They have gears designed to maintain lubrication with the recommended ATF and a completely different form of synchronization if any. Lots of fwd automatic transmissions have a seperate reservoir in the housing for the diff that contains gear oil because ATF would not be sufficient under the extreme pressure conditions of a modern hypoid diff.

Too high viscosity - increased friction and shearing leading to power loss, heat, oil degradation, and the hydraulic forces can be sufficient to break the gearbox in extreme cases.

Too low viscosity - wear, scuffing, adhesion even welding in extreme cases.

Why would current manual gearboxes be any different from older ones?

Older boxes were noisy and sloppy - designed with high pressure angles and clearances at the cost of noise and power to suit the lubricants available at the time. The ducato gearbox until the early 2000s is based on a 1960s citroen design.

There are current manual gearboxes in some vehicles that stipulate auto fluid, so doubt there would be any issues.

Yes designed to operate on ATF, there are also gearboxes that stipulate polyurea grease but you wouldn't put that in a ducato.

What alternative? Hundreds of pounds on a gearbox recon? If it doesn't work, what have you lost - a few quids worth of oil.

I 100% agree - *if* the OP has no plans to ever recondition the current box and is happy to replace it with a different new or used box if the experiment fails.

 

[oigle]

They have gears designed to maintain lubrication with the recommended ATF and a completely different form of synchronization if any. Lots of fwd automatic transmissions have a seperate reservoir in the housing for the diff that contains gear oil because ATF would not be sufficient under the extreme pressure conditions of a modern hypoid diff.
Synchronization is hardy as issue - auto fluid improves that anyway. The gearbox in question is not connected to a diff and FWD doesn't use hypoid.
Too high viscosity - increased friction and shearing leading to power loss, heat, oil degradation, and the hydraulic forces can be sufficient to break the gearbox in extreme cases. Auto fluid is 15/40 viscosity, hardly an increase over standard 80 weight gear oil

Too low viscosity - wear, scuffing, adhesion even welding in extreme cases. As I said, auto boxes use gears too with similar loadings so no value there



Older boxes were noisy and sloppy - designed with high pressure angles and clearances at the cost of noise and power to suit the lubricants available at the time. The ducato gearbox until the early 2000s is based on a 1960s citroen design.Worked fine on 1970's Mazda gearboxes.
Slightly more operational noise and a small increase in heat but never any failures.



Yes designed to operate on ATF, there are also gearboxes that stipulate polyurea grease but you wouldn't put that in a ducato.Hardly relevant



I 100% agree - *if* the OP has no plans to ever recondition the current box and is happy to replace it with a different new or used box if the experiment fails.

Of course, there has to be some risk but I would consider it worth the gamble. A full recon job to fix the synchros would also be quite exxy.
Appreciate your thoughts though...

 

[madwrx]

blimey thats low mileage for a box to pop a syncro -these are meant to be heavy duty vans? surely- the diff bearings on my 110k miles van are pretty noisy but the box is otherwise spot on

 

[Baden87]

Just had gearbox oil changed ,but this has made the crunching worse

 

[Baden87]

is this just me or is this a common fault on the Ducato

 

[oigle]

Just had gearbox oil changed ,but this has made the crunching worse

What oil did you put in?

And "yes", seems to be a common Fiat failure. The later "auto" boxes seem to sort it by doing quite slow changes automatically.

 

[Baden87]

So why has it failed at such low mileage ? My worry is spend £1000 getting it fixed ,only to have it happen again in another 29000 miles