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PostPosted: Sat Feb 21, 2015 5:01 pm 
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Joined: Wed Jan 29, 2014 1:18 am
Posts: 212
Location: Slovenia
so yesterday i was driving from work and at about 2500rpm in 4th gear (light acceleration) something broke in my gearbox.. when accelerating it all sounds ok, but when releasing throttle it makes trrrrr sound.. so i took apart my gearbox and find out few teeth on crown gear were broken and bottom bearing on pinion was destroyed..
all i want to know is, what do you guys think, did broken bearing damage crown gear or it was the other way? or maybe anything else?
it's GTi box with Gti 1-4 gears, 5th from GS
CWP is 4.92 (59x12)
helical/torsen LSD
both bearings on pinion and both on input shaft are SGP
both bearings on LSD are SKF
engine is stock, except 210/340 cams and sandros chip, full (hard) engine mounts and lower arm mounts
almost no left foot brake use
both axles have a little play tbh...

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PostPosted: Sat Feb 21, 2015 5:54 pm 
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Joined: Sun Aug 25, 2002 5:26 pm
Posts: 1930
Location: Etobicoke, Ontario
That bearing is NOTORIOUS for failure.

My transmission makes the exact same noise as you WITH a fresh rebuild which makes me think the bearing pre-load washer on mine is not the right thickness.

I have been driving it like this for months and months and it hasn't been getting any worse.

And the noise only occurs when NOT applying throttle right? Even in neutral and coasting?

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PostPosted: Sat Feb 21, 2015 8:13 pm 
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Joined: Wed Jan 29, 2014 1:18 am
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Location: Slovenia
that noise was there all the time except when applying throttle, but it was loudest when in gear and no throttle (so engine was slowing wheels down and "pressure" was on the opposite side of teeth than while applying thorttle)

my preload should be fine, same as stated in manuals..
4.92 FD is pretty loud by itself (not sure if that's because teeth size/shape or because of high ratio) but there was no trrr noise before.. it was just like buum, buum, bumm and from there on trrrr when releasing throttle..


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PostPosted: Sat Feb 21, 2015 10:20 pm 
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Joined: Tue Jul 03, 2012 12:19 pm
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Location: vancouver island, canada
the bearing went and took out the gear for sure.

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92 geo metro 1.0L 5 spd. 2 dr Soon to be my turbo swap car. (Dragonfly) sold
91 pontiac firefly, 1.0L 2dr auto. stock. (The crap can) sold
91 chevy sprint. 1.0L 5 spd. My first turbo swap. (Red rocket) now the purple nurple
95 geo metro. 1.3L auto parts car. (Scrap)
91 chevy sprint turbo, blueboy keeping it "stock"


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PostPosted: Sat Feb 21, 2015 11:00 pm 
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Location: Christchurch NZ, quake capital
Speculating here but it looks like the OD of your crownwheel is so big it touches the bearing cage with any thrust/axial force, it looks like under acceleration the countershaft moves away from the crownwheel, a little bit of bearing wear or too thin a shim under the bearing plate would allow the crownwheel to touch the bearing cage under acceleration which in turn will accelerate the bearing wear and cause more interference and eventually complete bearing failure.

What is the width of that aftermarket crownwheel? and more importantly the width from the centre line of the diff? does the crownwheel have a zero offset? I'm asking because the crownwheel contact patch may of been too low on the pinion gear and too close to the bearing race, hard to see when assembling because 1st gear is in the way.


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PostPosted: Sun Feb 22, 2015 8:25 am 
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Joined: Wed Jan 29, 2014 1:18 am
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Location: Slovenia
Dattman wrote:
Speculating here but it looks like the OD of your crownwheel is so big it touches the bearing cage with any thrust/axial force, it looks like under acceleration the countershaft moves away from the crownwheel, a little bit of bearing wear or too thin a shim under the bearing plate would allow the crownwheel to touch the bearing cage under acceleration which in turn will accelerate the bearing wear and cause more interference and eventually complete bearing failure.

What is the width of that aftermarket crownwheel? and more importantly the width from the centre line of the diff? does the crownwheel have a zero offset? I'm asking because the crownwheel contact patch may of been too low on the pinion gear and too close to the bearing race, hard to see when assembling because 1st gear is in the way.


can't look if cw teeth touch bearing as i don't have any good bearing around right now, but on pinion there is sign of cw teeth touching it about 1mm from bearing..
anyway i'm rebuilding it with different bearing (1mm lower and shim between bearing and pinion teeth) since i can get it for about 10eur from local shop while original bearing is SGP only for about 50eur from local suzuki dealer..

will look into this another day for sure, thanks for info (we have another gearbox with 5.45 FD (11x60) on our racing car so i'm a little worried about that bearing on it.. thinking about pulling it apart and check it out :D


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