ok, so after a few years of on and off 6n ownership I'm more than aware of the usual box problems. i occasionally work at a gear specific engineers (dont ask) and have spoke to a few of the lads about nocking up some replacment shafts out of something a little stronger, as the only thing i can assume is the stock shafts flex and this is what kill box's, if the gears are too soft these can also be remanufactured..

so my questions are thusly, who would be interested, does anyone have imentions of a NEW shaft (no good messuring up off of an old one, tech drawing would be lovely) and are there any selector forks that are more up to the job i could use as replacments? all the above bar the casing can be machined, I'm going to price it all up anyway. the cases i could nock up from a few chunks of billet but the cost would be astronomical and itd be better to do another box and nocking up a bellhousing. the remachining of anything is not a problem, I'm thinking more along the lines of doing 100 or so of these on a recon basis (once I've built and run one for a good hard couple ten thousand miles) and want to remanufactor as little as possible, hopefully ill get away with new forks, new shafts and decent second hand gearsets/synchro parts. any other known weaknesses inside the box people know of? I've not been round vw's for a couple years and can bearly remember the last box i had in bits. the only reason for this idea was a convo with a few fellow engineers in the exact position to make these bits for me. well, that and the fact i know people want a type 085 replacment that can actually handle enough power to pull skin from your favourite sunday after dinner treat

Well the common faults seem to be the diff bearings and 5th gear alignment and the typical wearing out of the synchro on 2nd gear. I'm not sure about the shafts being a problem?

bearings failing would be down to ether undersized for the workload, or side load caused by flex on the shafts, would also explain why they shred gears in some cases without the bearings taking a hit.. and why does 5th need ajusting? gear wear? diff bearings can be common to any box's. not that the germans have lazy days, but they should be built, messured, rebuilt shimmed correctly, machining identical parts and fitting identical parts doesnt always = perfect shim size out the packet. the bearings themselves could be crap from the box, but there german bearings... well, the germans were happy to use them.

ether way, i have the ability to refabricate ALL the gears, in any ratio that will fit in the box, remachine shafts, scorce better bearings (anyone tried ceramics?) and so on, so may aswell tackle the problem facing half the vw comunity lol any sudgesgions welcome. I'm trying new shafts,fresh bearings, correctly shimmed diff for myself just to see how it handles it.. 1.8 8v should show any weakness I've been told lol

The weak bearings are on the differential and not, afaik the bearings elsewhere in the box. It might be fairer to say the diff bearings go before the rest get a chance! I suppose wear on the diff bearings is going to lead to other problems like wear on the layshaft output gear to the differential.

5th gear has the hardest job and the engagement ring wears and can strip it's teeth. This is exacerbated by wear on selector forks and low gearbox oil. If the oil is below the level of the fork head then the wear gets accelerated.

Custom gear ratios is an interesting proposition! :)

When mine went i stripped it and found the bearings had collapsed for 5th + second

Needle bearings? They are pretty tiny!

I wish '085s had an oil dipstick!

EDIT - I didn't see the pic! Thought you meant the bearings that go inside the gear cogs and not the bearings on the shaft. So no other wear other than shaft bearings? were these on the input shaft or layshaft?

I've been looking through rebuild threads/rebuild vids and generally looking through forums for a couple weeks... and from what i can tell the ley shaft bearings go, due to side load/bendy shafts, this then leaves slack on the ley shaft,.. this then pushes downwards against the diff (conical cut gears) thus pushing the diff hard upwards thus killing the left side diff bearing. so ether the bearings are absoloute cheese, or the shafts are bending, theres really no other explination for the diff bearings. flex in the shaft WILL kill a bearing, wich WILL push on the diff meaning all the work is on one bearing and guess what, its always the one that go's and the ley shaft bearing is usually in worse shape. I've spoken to a few of the lads at the gearshop and they tend to agree fromthe damage present in most cases that the shafts could well be flexing. unless of course someones found another problem/could shed some light on why these box's are so rubbish

Needle bearings? They are pretty tiny!

I wish '085s had an oil dipstick!

EDIT - I didn't see the pic! Thought you meant the bearings that go inside the gear cogs and not the bearings on the shaft. So no other wear other than shaft bearings? were these on the input shaft or layshaft?

Not massively got with technical terms so I dunno haha.

Here's another pic and il poorly explain where it was to see if you know the one I mean.

Basically next to the big cog (right side of the pic) there is a indent for one of the shafts, its te bearing that sits in that recess so only spins in that recess and doesn't touch anything else

Edit: nothing else needed changing

Edited 7 February, 201313 yr by matt01

If a shaft flexes whilst being turned, it tends to snap. Of all my breakages i've never considered a shaft flexing, though all suggestions welcome.

My failed bearings have usually had craters in the surfaces, overheating and foreign objects seemed to be the problem. Linkages have very much been a problem, especially 5th where the gear is right next to the bearing so shaft flex isn't an issue, but there as with the set generally these gears and sync rings are generally small and narrow - there's just not enough meat on anything. Teeth are shredded because they're simply too small. And i see possibility for stronger shafts to actually transfer more energy into the weaker parts and make them fail earlier..

I like the enthusiasm, but I'm not sure you have really considered what's involved in transmission design, i hope this doesn't come across as condescending, just a few questions that might clear things up.

How do you plan to validate that what you are designing is better than the existing parts?

In the OEM industry when benchmarking a gearbox, you'll have the gear pairs fully inspected for parameters like tooth module, helix angle, pressure angle, facewidth, contact ratio, hardness, case depth and material composition. Then a model can be created in whichever simulation software you choose, a duty cycle input and a gear life calculated. Similar process for the bearing lives, duty cycle, geometry and some maths, and you'll have a benchmark.

Now you can begin to design something to suit the new power requirement achieving an appropriate life.

Ratios first, how had you planned on selecting these?

Synchros? Retain/replace with a dog engagement setup?

Once you have some geometry, then comes material selection and heat treatment?

Transmission design is not just a case of going to chap with a lathe, a hob and some EN24.

The Engineers who designed the 085 box were not having an off day, they designed a box to suit the specification within the budget. Putting them into a heavy 6N was not the finest idea from VW I'll admit, but then neither was designing the 6N

You canna change the laws of Physics....

From all the boxes I've had apart the lay shaft bearing seems to go before the diff bearing. From what I gather its due to over heating and I'm guessing this is due tothe oil level in all of them being too low. The only reason for this that I have found is the selector shaft oil seal. If there was a way of perhaps improving this, or making a more heavy duty seal, then in my eyes this is the way forward. I haven't heard of the input shaft oil seal failing ( so far) so maybe it is down to material? Other gearboxs in other cars can go for decades without losing a drop of oil.

Interesting thread I'm book marking this

Yeah, it got really far after Pete's answer..

Someone needs to try the 02K in a Polo. I have one in the garage but the Golf is designed for the 02x boxes so shafts and mounts are readily available.

I've already fitted an 020 to a polo block

I'm now going to be using an 02M 6 speed box mated to a Lupo Gti block though for power needs more than anything else

The 02A fits in the polo engine bay without too much modification

Just the mounts on the gearbox side that need altering mainly

Edited 13 March, 201313 yr by StinkyPete

Linkages?

The 020 used stick which can be done but can also be converted to cable making it alot easier to do