Why this thread started...
I'm planning on stripping my gearbox, rebuilding ALL seals and ALL bearings. A guide will be made in due course. My gearbox is fine.. But we all know for how long??
I think it's important to find out what is actually wrong with the gearboxes and I firmly belive in prevention rather than repair. In 5 years time this gearbox problem WILL be the death of most GTi's causing them to be scrapped/stripped.
I'm just trying to build up some information on what fails and why as all the information so far is here there and everywhere.. it's also very inconsistent.
What I have found out so far:
Gearbox Type: The Polo GTI gearbox is part of the 085 gearbox family, which as I'm told is a gearbox design which goes back to the 70's with the mk1 small block golfs and mk1 polo's.. The Polo GTi box is just a revised version and can trace it's heritage down to the original 70's unit, which probably explains why it's so rubbish by today's standards.
The Polo GTi Box Codes Are:
ETG and
FFW - Now as far as I'm aware, they are identical, casing and internals. If anyone has anything to prove otherwise please let me know. Mines a mid 2001, engine code AVY with a FFW gearbox, according to the VW sticker in the boot.
What Else Fits: I have been told that Lupo Sports, Arosa sports and Polo GTi's all share the same type of gearbox, different codes across the range, but apparently the same externals, internals and ratio's. All other Lupo/Arosa/MK4 & 5 polo gearboxes also fit (bar the Lupo GTi due to a different design in bell housing) but expect different internals and therefore ratios, but they do physically fit. I will try and find different code's for these boxes which are apparently the same and also confirm that this statement is true.
Leaking Seal: The shaft selector seal is prone to leaking, part no: 085 301 227 from VW or TPS. If it's left to leak the oil will go low and cause the gears to be un-lubricated (mainly 5th and 4th as they sit highest in the casing). Check at the back of the gearbox where the big shiny rod pushes into it. The seal will be covered with oil and be dripping if it's shagged (it should be moist, but not wet and dripping). If 5th gear is whining or constantly pops out, low oil is usually the cause.
Gearbox Oil: The polo Gti gearbox uses 75w90 Oil (fully synthetic) or equivalent. VW stuff is constantly remarked as the best oil to use, although it doesn't say 75w90 on the tub it is the same apparently and 2.7 Litres is the amount needed. Part Number is G060726A (for 1 ltr) - In total this cost me £17.06 retail for 3 litres (Sep 2010). You can check the level by undoing the top oil check/fill bolt (imagine a female version of a 17mm bolt) and can be found on the front of the gearbox bang under the plastic runners which the loom fastens to, this is done by using a 17mm hex bit (basically a massive 17mm allen key/allen bit). Once the bolt is out (will be very stiff) the oil should be level with the lowest part of the open hole (when the car is level), it should just (only just) drip out really. If not, top up/change the oil. To drain the oil undo the bottom bolt (back of gearbox) of the same design as the check/fill bolt. To top up the oil use a funnel with a hose attached to the bottom (can be bough complete or just bodge one) and fill from the top fill hole (the same you check the level with). DO NOT put oil down the hole at the very top of the gearbox, thats for checking the flywheel you numpties.
It is highly recommended that the gearbox oil is changed yearly at least, those people who have commented on high mileage original gearboxes always state on changing the oil at regular intervals (same intervals as engine oil change), 6k intervals have been commented...! To say how easy/cheap this is to do why would you not bother? I personally would change the gearbox oil yearly due to the fact that gearbox oil should be lifetime, so a year won't be too bad. Plus, may I add, most people comment on how much smoother their box feels after a oil change.
Why they fail: The differential is fastened together using a soft metal rivet (Older 085 gearboxes use a harder, but smaller type rivet. Newer 085 gearboxes such as the GTi box use a larger rivet, but with softer metal - It's not up to the job). These rivets wear and/or shear off causing excessive play within the diff (or in some cases damage to gears by flying about metal fragments - or even holes in casings!). This damage/wear in turn causes differential bearing wear, leading to play and/or failure of the bearings and diff, which at the same time puts stress on the rest of the gearbox (usually the output bearing and shaft which is bang next to the diff). By drilling the rivets out and replacing them for a high strength nut and bolt, it should stop this happening in the first place.
Now, when the gearbox starts whirring/whining, it's a sign that the bearings are on their last legs, apparently by replacing these bearings immediatly it should avoid any damage to the gears/shafts. Now, research has shown no regular time scale on when they can blow, some people report months of whirring until the gearbox poo's itself, other people report a matter of days. Some people have reported no tell tail signs at all, apparently the box just goes (if this happens I feel for you).
It is recommended that once the gearbox show's signs of failure, get it repaired pronto, if left to actually blow it'll cost more in the long run as damaged shafts, gears and holes in the casing can be caused. Which in my opinion is why some refurbished gearboxes seem to pop again very shortly afterwards, whether that be poorly refurbished units or worn gears/shafts which wear even quicker with new parts bang next to them (a bunch of high stress parts moving at high intensity, the weakest is going to fail, right?).
Obviously like all moving parts, wear naturally happens over time. Bearings as such are prone to this. But... Rebuild kits are available from VW.
Part numbers are here:
085 311 123 D - x3 - 2xLayshaft bearing, 1xMain Shaft bearing (ETKA Confirmed - Taper Roller Bearings)
311 405 625 F - x1 - Mainshaft bearing (ETKA Confirmed - Taper Roller Bearing)
411 501 283 G - x2 - Diff Bearings (ETKA Confirmed - Taper Roller Bearings)
085 311 431 C - x1 - 5th Gear Idler Bearing (ETKA Confirmed - Needle Bearing)
085 311 113 - x1 - Seal (ETKA Confirmed - Oil Seal)
084 409 189 C - x1 - Diff Seal (ETKA Confirmed - Oil Seal)
084 409 189 B - x1 - Diff Seal (ETKA Confirmed - Oil Seal)
085 301 215 A - x1 - End Plate Gasket (ETKA Confirmed - Gasket)
085 311 582 - x1 - Crappy Clip Thats Bound to Break, holds in selectors. (ETKA Confirmed - Securing Clip)
085 301 227 - x1 - Shaft Selector Seal (Etka Confirmed - Radial Shaft Seal)
This piece of information was also included: " If you want to 'Upgrade' the only thing which can be 'upgraded' is the plastic 5th gear bearing with a metal item but TBH so long as the gear oil is changed regually it should be fine."
I have been told that by taking the plastic bearing into any bearing shop, one can be made up, apparently. But just google "085 rebuild" and you'll find countless kits consisting of 6 bearings and 3 gaskets, a full kit, priced between £50 and £150 for what looks like the same kit (well for the bearings and seals anyway). I'm sticking with VW when I do mine because I don't know any better, I'm an OE whore and also it's proven that these gearboxes can last with the correct maintenance.
I copied the above information from various forums around internet, whether these are correct or not I don't know.. I have checked out ETKA and all parts are confirmed and look correct (as of Sept 2010), may I also add that these are the exact same part numbers used in old polo's and golfs right back to 1982 when they all had about 60bhp, fills you with confidence doesn't it? You could imagine the conversation over at VW when building the GTi.
"Hey Hans, you know ze new Polo GTi ya?"
"Ya?"
"Ve can not be bozered to make a new gearbox ya?"
"so vhat vill ve do?"
"Use ze same partss as all ze old poloss ya?
"Ya, zhat vill last, ze GTi hass two Timess ze power!"
"ve vill make lotss of money from ze rebuild ya?"
"Hahahahahaha"
Conclusion (yes I'm a geek 
):
My research has all pointed to the same thing: The diff rivets wear/the bearings wear followed by the shafts/gears due to excessive play then it goes pop. Whether this be from poor design, a leaking seal and therefore low oil causing wear, poor maintenance or just plain ragging of the gearbox I am unsure of. Probably a combination of the lot.
But if the above statement is true, and If the problem is treated before any major damage is caused, I can see new seals, oil, bearings and bolts on the differential fixing the issue, in my opinion of course . If your gearbox has gone bang, your in tough luck and a rebuild is needed as I wouldn't know where to start in replacing other things as quite frankly I hate gearboxes and fiddly things.
I have been told that this should cost around £100-£150 (all bearings/seals and gearbox oil). Better than a £600 rebuild eh?
P.s.
Just to add... There are plenty of original gearboxes with over 100k (mines original and on 113k!).. So it's not a fault with all, I think regular services and checking of gearbox seals for leaks will prolong the life of the gearbox. It's like anything, if you look after it, it'll last forever. If you don't it'll die.
The gearbox is a known issue, so just take that in stride and look after it, maintain it regulary and it'll last you the lifetime of the car.. Hopefully...
**** This is all information I have gathered whilst researching and speaking to VW geeks, it's all my own finds and nothing is proven by myself so I don't want to be held accountable, but I am pretty confident if you do the research you'll find the same answers. It's just hours and hours of research I have found whilst I should be doing real work, if only my boss knew ****
If anyone has anything to add, or disagree with what I'm saying (with proof) let me know and i''ll amend the info.
plenty more are waiting to see what you come up with
