SyncroGhia wrote:A good illustration of what goes wrong inside a Syncro or 2WD gearbox.
This is an illustration of a 5 speed 2WD gearbox but as the Syncro gearbox is basically the same (for the purposes of this post), we can use this to illustrate what happens when pinion or mainshaft bearings wear or move.
When you hear someone saying that "the pinion bearing has failed", it means that it's worn enough for the pinion shaft to be able to move forwards and backwards in the case.
This does a number of things. Firstly, it moves the pinion head away from the crown wheel/ring gear so that the mesh pattern is no longer correct and the load is no longer spread evenly across the majority of the teeth of both the crown/pinion. There is an audible change when the shaft moves from it's furthest point in one direction to it's furthest point in the other direction. Obviously this will be when you are on and off throttle as the load changes respectively. This wears the crown/pinion very quickly through the hardened surface and causes the pitting on the teeth closest to the smallest end of the pinion and then starts taking chunks out of the crown wheel/ring gear!
The second thing is that with the pinion shaft moving forwards in the casing, G gear (in a Syncro) or 1st gear (in a 5 speed 2WD) gets squashed between the Synchro hub (which is fixed to the pinion shaft) and the support bearing in the end casing. The more the pinion shaft moves, the more load goes through to this set of components until the needle roller bearings (which are supporting G or 1st gear) get squashed, the bearing surface on the pinion shaft gets knarled up, G/1st gear gets knarled up and the small bearing in the end of the casing dies. Very messy. Believe it or not, this in itself doesn't create a whole lot of noise so the only way you know something is wrong is from the noise from the crown/pinion being in the wrong position in relation to each other.
In extreme cases (no pun intended), 2nd gear (in a Syncro or 3rd in a 5 speed 2WD) get's squished as well and it becomes impossible to select it without a huge crunch!
If your gearbox is noisy... there's a reason!!
Ok onto the mainshaft.
I've just put the spare gearbox into Limey because it started jumping out of 4th gear (5th gear in a 5 speed 2WD). The reason for this was that the mainshaft bearing was moving in it's casing. This was allowing the whole mainshaft to move forwards in the case.
If you look at the mainshaft bearing, to the right you'll see a gear. Right again from that are 2 sets of smaller teeth and then the selector ring. When you select 4th gear, you pull the selector ring over both of the smaller sets of teeth between the selector ring and 4 gear. If you imagine the mainshaft moving forwards (or to the left for this illustration), the selector ring would stay in it's normal position and effectively move to the right... heading back towards neutral. This puts your selection of the gear only half in/out. If you've ever missed a shift, you'll have 'half' selected the gear and the gearbox throws it back out of gear. This is what my gearbox was doing in Limey.
The cut of the gears cause a load pulling the mainshaft forwards in the case.
The mainshaft bearing is held in place by the next housing and by the bearing being a very snug fit into it's casing. However, if the bearing can move just a little... it slowly hammers a bearing shaped imprint into the next casing. If you have lots more torque than standard (like Limey) then this problem is made worse. If you're towing over 3 tons at 60 mph up a hill flat out with lots more torque... this is made much much worse
You can see the 'hammered' imprint in the R+G housing here.
I hope this helps anyone wondering what goes wrong inside a T3 gearbox.
MG
What goes wrong inside a T3 gearbox / transmission
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What goes wrong inside a T3 gearbox / transmission
I saw this on Facebook, it's taken from the Samba forum written by Michael Ghia
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Re: What goes wrong inside a T3 gearbox / transmission
This is interesting.
A while back my clutch cylinder packed in and I had to constantly pump the clutch to select gears. I managed to get the van into my garage but it was stick hard in first gear. From what I remember in my fit or rage at the time I may have rammed the gear lever into 1st with the clutch not fully disengaged due to the cylinder issues.
Once it was in the garage I could not get it out of first gear and so again, in my stupid fit of rage forced the lever out of first with the engine off. I am a strong guy and I dread to think what kind of force I applied! I swear I remember hearing a 'ping' as if something had fallen to the floor, but I never found out what it was.
I fixed the cylinder and was able to use the clutch again, however now the gear stick feels very loose and sloppy and most worryingly, I have to double clutch to get it into 3rd without crunching. If i try a straight gear change from 2nd to 3rd without going to neutral, releasing the clutch and repressing it to go into 3rd I get a nasty crunch as it goes on. This only happens when changing into 3rd.
So now I am thinking what this might be and how I can fix it. I am considering replacing all the gear linkage bushes (onion, mid and selector joint) and hoping / praying that fixes it.
Does anyone have any idea what I may have done? Is it possible to damage the gearbox itself in this way? Or more than likely have I damaged / mis aligned the gear linkage?
If the clutch fluid wasn't properly bled could that cause only one gear to crunch or would it be for all?
Thanks in advanced guys. I live abroad at the moment and so want to work on the van when back for a few weeks this summer.
A while back my clutch cylinder packed in and I had to constantly pump the clutch to select gears. I managed to get the van into my garage but it was stick hard in first gear. From what I remember in my fit or rage at the time I may have rammed the gear lever into 1st with the clutch not fully disengaged due to the cylinder issues.
Once it was in the garage I could not get it out of first gear and so again, in my stupid fit of rage forced the lever out of first with the engine off. I am a strong guy and I dread to think what kind of force I applied! I swear I remember hearing a 'ping' as if something had fallen to the floor, but I never found out what it was.
I fixed the cylinder and was able to use the clutch again, however now the gear stick feels very loose and sloppy and most worryingly, I have to double clutch to get it into 3rd without crunching. If i try a straight gear change from 2nd to 3rd without going to neutral, releasing the clutch and repressing it to go into 3rd I get a nasty crunch as it goes on. This only happens when changing into 3rd.
So now I am thinking what this might be and how I can fix it. I am considering replacing all the gear linkage bushes (onion, mid and selector joint) and hoping / praying that fixes it.
Does anyone have any idea what I may have done? Is it possible to damage the gearbox itself in this way? Or more than likely have I damaged / mis aligned the gear linkage?
If the clutch fluid wasn't properly bled could that cause only one gear to crunch or would it be for all?
Thanks in advanced guys. I live abroad at the moment and so want to work on the van when back for a few weeks this summer.
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Re: What goes wrong inside a T3 gearbox / transmission
Mike is well placed to lecture others about shredded 094 transaxles
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Re: What goes wrong inside a T3 gearbox / transmission
Good find Kev. Never quite sure what to do with my 5 speed box. It runs fine but if it ever goes I'm right up the shoot....
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Re: What goes wrong inside a T3 gearbox / transmission
My 5 speed makes a loud rattle in neutral. Louder when everything is warmed up. Disappears totally when you press the clutch. Something strange going on in there!
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Re: What goes wrong inside a T3 gearbox / transmission
boatbuilder wrote:My 5 speed makes a loud rattle in neutral. Louder when everything is warmed up. Disappears totally when you press the clutch. Something strange going on in there!
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that's the input side, could be the clutch rather than the gearbox, mainshaft bearing on the input side tends to grumble when worn or displaced, but if it is then everything is running out of position so may be noisy, rattle likely to be clutch or exhaust
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Re: What goes wrong inside a T3 gearbox / transmission
I wouldn't trust anything Ghia posted anywhere, not trustworthy source of anything , just a slimy wideboi
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Re: What goes wrong inside a T3 gearbox / transmission
Quote from Aidan about my 4 spd box-
"The 3rd gear worn out synchroring on a 4 speed is usually a symptom of the pinion bearing being worn allowing the back of 2nd gear to run against the back of 3rd gear pushing it into the synchroring and wearing it prematurely so expect to be doing the whole job; this isn't fatal on the four speed because there's no gear hung out the front, the same wear in a five speed means serious damage to 1st gear and potential major failure."
"The 3rd gear worn out synchroring on a 4 speed is usually a symptom of the pinion bearing being worn allowing the back of 2nd gear to run against the back of 3rd gear pushing it into the synchroring and wearing it prematurely so expect to be doing the whole job; this isn't fatal on the four speed because there's no gear hung out the front, the same wear in a five speed means serious damage to 1st gear and potential major failure."
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Re: What goes wrong inside a T3 gearbox / transmission
Never mind all the BS merchants and the copy/pasters THIS is what kills many 5 speed boxes ..
4th/5th Synchro hub out of our box that failed as we cruised to a stop in a Belgian gas station on the way to the Czech Republic. This one's glued back together, as you will see, and lives on my office window sill as a reminder to never ignore that tiny thing that's niggling you as it may escalate very quickly at the wrong time/place.
Ian
4th/5th Synchro hub out of our box that failed as we cruised to a stop in a Belgian gas station on the way to the Czech Republic. This one's glued back together, as you will see, and lives on my office window sill as a reminder to never ignore that tiny thing that's niggling you as it may escalate very quickly at the wrong time/place.
Ian
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Re: What goes wrong inside a T3 gearbox / transmission
I was getting worried that my 5-speed may have been playing up after fitting a new (prototype) gear lever assembly, turned out it was just poor adjustment of the linkage: it was set too long and the lever forks were sitting right on the corner of the pyramids when in 4th. So it popped out on the overrun! 10 mins under the van with molegrips and a mallet, all sorted.
I think I now have the slickest 1-2 shift of any 5-speed T3 transmission
PS renewing both the master and slave cylinders for the clutch made a huge difference.
I think I now have the slickest 1-2 shift of any 5-speed T3 transmission
PS renewing both the master and slave cylinders for the clutch made a huge difference.