Weaknesses of the 020, and "Dual Synchros"..?

I'm interested in the common modes of failure of 020 boxes. So far I'm aware of the following two:

- Sheared diff rivots causing catastrophic failure

- Worn Synchros in first and second causing crunching and notchyness when selecting gear

I know the diff rivot problem can be sorted by fitting a bolt kit; but haven't really heard about any solutions for the weak synchros. I've been looking at 02K boxes for various reasons (which appear to basically be an 020 with a different clutch casing / bellend housing) and stumbled across this on the eurospec site which refers to the fitting of "Duel synchros" to first and second which "increases ease of operation and the lifespan of the synchronizers".

Looking at ETKA the synchros (used on 2nd and 3rd at least) are the same on the 020 and 02K boxes; soooooo... if one is having an 020 box rebuilt, would it be possible / adviseable to fit such dual synchros (assuming they could be sourced separately)?

Are there any other inherent weaknesses in the 020 box; bearings / shifter mech perhaps? I'm hoping that ultimately it might be possible to rebuild a strengthened 020 that would last longer and take more torque, and perhaps negate the need to fit cable change boxes on 1.8T conversions etc.

Anyone got any thoughts?

 

020 upgrade

TBM,

I share your interest, am aware of similar weaknesses, and suspect the majority of other failures are due to spirited use of a poorly maintained transmission exacerbated by dirty, insufficient, or incorrect lubricant[:^(]

Regarding the Eurospec "dual synchroniser assembly for 1st and 2nd gears", as the saying goes, "show me the money", in this case a parts view please, without which their claim should be filed under "marketing 101"

Let's hope experienced, alert rebuilder's such as HotGolf and Broke may feel inspired to contribute their insights as to weaknesses other than diff rivets and syncro rings, points of interest being - -

- - signs of bearing races galling, or other symptoms typical of overloaded bearings - - and if so, is there sufficient space to substitute a more robust bearing including additional machining of case and/or shaft if required?

- - signs of stress on the teeth, including pattern changes caused by the shafts flexing under load or the case distorting

- - similar to above, but caused by inferior material or heat treatment

Not sure when this update was introduced, but photos of some, presumably newer 020 transmission cases shows that additional material has been cast inside the case around the main and layshaft bearing bores, presumably to prevent extreme forces from forcing the shafts apart by distorting the case, and/or to increase the case bore surface areas to accommodate larger diameter or longer bearings

It also appears some of our Scandanavian peers are running 020's under rip snorting turboed ice racing and rallying cars, with cases further strengthened by machining and fitting an aluminum brace to the exterior of the case

The brace looks like a scaled up bicycle chain outer link, the case exterior being machined concentric to each shaft axis so the brace can slide over the protrusions so created

Follow up with quality bearings, a bolted or slippy diff, carbon instead of brass synchro rings, cryogenic treatment of all ferrous components except bearings, skillful assembly, correct lubricant, and away she goes - -

 

Tell us more.

With photos, or links if possible?

A few part numbers gleened from www.wagenstad.com:

1998, 1997
4 020 301 103 AR transmission case 1 CHD,CHB,CHE, CHC,DFQ,CJF, CRY,CYZ,CZA, CZK,CQB,CYY, DFP,DFN,DFW, DFX,DGE,DGG, DGL,DGH,DMM, DGM
(4) 020 301 103 BE transmission case 1 CYW,DFY

1996
(4) 020 301 103 AR transmission case 1 CHD,CHB,CHE, CHC,CHV,CJF, CRY,CYZ,CZA, CZK,CQB,CYY, DFP,DFN,DFQ
(4) 020 301 103 BA transmission case 1 CDJ
(4) 020 301 103 BE transmission case 1 CYW

1995, 1994
(4) 020 301 103 AR transmission case 1 CHD,CHB,CHE, CHC,CHV,CJF, CRY
(4) 020 301 103 BA transmission case 1 CDJ

1993
(4) 020 301 103 BA transmission case 1 CDJ

1992, 1991, 1990
(4) 020 301 103 AR transmission case 1

1989
No Info.

1988
4 020 301 103 AJ transmission case G >> 30 09 7* 1 4S,4T,2Y, ACD,ACN,AEN
4A c 020 301 103 AK transmission case G >> 30 09 7* 1 9A,ACL,AGB, AGS

1987
4 no longer available 1 4S,4T,2Y, ACD,ACN,AEN
4A c 020 301 103 AK transmission case 1 ACN,AGB,AGS

1986
4 020 301 103 AJ transmission case G >> 30 09 7* 1 4S,4T,2Y, ACD,ACN,AEN
4A c 020 301 103 AK transmission case G >> 30 09 7* 1 9A,ACL,AGB, AGS
4 020 301 103 AJ transmission case G 01 10 7>>* 1

All use the same bearings:
5 020 311 123 N ball bearing 26X68X21,6 1
35 311 405 625 F taper roller bearing 29X50,29X14,73 1

 

Misplaced contacts

Blimey Daved, that's an impressive list that I'm too tired to study right now!

The case strengthening brace was mentioned to me by a Norwegian or Swedish enthusiast about three years ago, bcgti (before ClubGTI) when I first searched for information on these transmissions - - believe he was with fff (fast fruit?) and was cheerfully informative in the several emails we exchanged - - sorry, but my former laptop crashed soon afterwards and I lost his contact details - - perhaps an inquiry to that club might elicit further information?

I noticed photos of 020 cases with differing amounts of material cast around the main and layshaft bearing bores in several different posts, one may have been Broke's, others ClubGTI, VWVortex, and elsewhere - - didn't think to record them for posterity as I was satisfied with what I'd observed, oe modifications such as this are not unusual, and at the time I didn't anticipate contributing to an on line discussion on this or any other subject

 

Thanks for the replies gents - glad to see I'm not the only one interested in this area

I'd agree; my own 'box whines in most gears; a problem I think made worse by low fluid levels thanks to the leak it's had for ages.. something else I was going to investigate was more modern oil types and bearing alternatives (either larger or higher spec in the same dimensions).

Yes, I've contacted them to see if they think these parts will fit an 020 and how much they'd cost if they were willing to supply them; not heard back yet. Assuming the parts are more than marketing hype, the only thing that concerns me is that were they interchangeable with the 020 items I'd have thought eurospec would have twigged that there'd be quite a market for them; making me think they don't fit for some reason..

Yup; hoping some of the forum's more knowledgeable members might contribute; haven't contacted anyone individually though since I know people are busy and don't want to waste their time. Insight from people with hands on experience of numerous different boxes would be invaluable though

I don't think I've ever heard of an 020 that's suffered failed gearsets - presumably because something else breaks first

Very interesting (nice harvest of part nos. Dave)- didn't think about upgrades in case design although it's totally plausible.. something else to while away countless hours hunting on the internetz, then

 

I have heard of 020 5th gears stripping their teeth on high output engines before. Just another fault over and above those mentioned above.

If you install a lower final drive ratio you reduce the stress internally in the box due to mechanical advantage.

A well built box with lsd eliminates diff pin, and diff rivet issues. So that along with a lower final drive and decent lubrication should create a more reliable box.

I have stripped many standard gearboxes that operated quietly in use on the road prior to removal. It was surprising how many had bearings on the way out due to case hardening beginning to fail, yet did not show any symptoms.
I suspect a lot of the boxes you hear that fail are old, beginning to wear and have the old original lubrication still in them.

I still have an 02K box here. On the back burner until I hear what is happening with a 1.4 16v engine.

 

I had a fifth gear go on a then recently rebuilt / Quaife`d 020 ... was put down to an inherent gear weakness ... a known problem. Engine was not a high output though (140bhp).

This box now has Gemini (5 speed) internals which help ...

Apart from that both 020`s I`ve run (rebuilt with Quaife`s) have been excellent, one with 200bhp (2Y standard internals + 4.25 FD).

 

There are a couple of different styles of 5th gear come to think of it. One with many small teeth, and another with fewer larger teeth. Much the same ratio between them.
I think difference is down to the 8v 0.89 (small teeth) and 16v 0.91 (larger teeth).
It could be one style is stronger than the other.

 

That's a bit crap about the 5th; will have to add that to the list and see if either type of gearset has a better reputation than the other..

I see the point about a lower FD, however this obviously isn't always practical - think of the long motorway journeys!

Danster - some interesting reading on the 1.4 16v engine here

 

020 expose

Daved, Danster, and of course TBM

Wonderful stuff, to which I'd like to contribute an 020 gearset identifier spreadsheet but, lacking the skillset to create such and/or post it, am sending a hwl (hand written list) pdf to the former two by pm

 

Larger teeth stronger in the root, but tend to wear more!

The correct lube solves this problem!

 

@LcT.

Why send it to me?

I hate Spread Sheets, the spawn of the Devil!

Designed by accountants, for accountants, to accountants!

I shall attempt to Mathcad 2000 it though!

Thanks,

Dave.

 

A small aside:

Back in the day, 1950s and 1960s, when **** and Volvo were the only Rally Teams building Proper Forest Cars, the saying was:

"Volvo thank God that **** put a 35 bhp gearbox into their cars."

In the end, **** made their gearboxes from Cast Steel to stop them blowing apart!

The point being:

The 020 box was designed for the 1.4/1.5 litre 827 block engine @ 65/70 bhp!

It did well to take the 170+ bhp of the Gruppe A VWMS 8vs!

 

VWMS 16V Gearbox.

Don't forget that a transmission oil cooler was used on the VWMS set up!

AJ Case - #1






STEEL Syncro Rings:

#55 x 4 Off 2nd to 5th Gear - 020 311 295 SP
#84 x 1 Off 1st Gear - 020 311 247 SP

VWMS 2nd - V03 703 748 : z = 33

 

Standard 020 FD 5th ...

 

FD is the code for the early close ratio 020 gearbox and uses the 0.91 ratio 5th with gears of 34 and 31 teeth.
It looks like the larger teeth to me.
The mk2 8v GTIs used similar gear ratios but with an ever so slightly higher 5th of 0.89.

The mk2 16v used the gearbox code 2Y which retained the lower 0.91 5th.......one can only presume this was due the lack lustre performance of the KR, so it needed a lower gear as it lacked the torque to pull the 0.89 ratio.

 

What do these Avanti 020 Dog Box Sets cost, one wonders?

 

Thats an 02a in the pic, do they do an 020 kit??

Saw this thread a few days ago, and haven't had a good chance to look things over. I'm assuming the 02k twin synchro system will go straight into the 020 box, as from what I've been told the crown/pinion kits you can buy for the 02k go directly into the 020, making the gear spacing the same. The 02a had 1st changed to this setup which means buying a new gear, 2 x synchros and a friction ring that goes between the two. The gear alone was around 140 from what I remember but would only remedy premature wear and make a smoother shift, but wouldn't increase the strength of the gear.

Have a question regarding the larger teeth being stronger? Is this really the case, as a fine pitch thread is usually stronger than a course pitch(more surface area) so would it be the same in the instance?

Good find though on the dual sync's, although you have to bare in mind that the 020 boxes are very old, and most have more than 100k, so the std synchro hasn't done too bad considering the mileage. Same goes for the gears. Most boxes have had little or no maintenence and most have far from the right level of oil, so no wonder things start dying. If the gears are already fatigued then eventaully they're going to give in. Would it be cost effective to start changing all the 'hard' parts of a box?

 

They state 020 on their web site?

VOLKSWAGEN GOLF GTI020
Gearbox 5 Speed Dog Gear Kit with limited slip differential
and new final drive
http://www.avanti-motorsport.com/gearbox1.htm​

Regarding gear teeth strength:

Bending Stress ∝ (Load x Diametral Pitch) / (Width x Lewis Factor)

For example:

Take two straight spur gear sets, where the gears are the same diameter. One with z = 20 teeth the other with z = 16 teeth.

If both have the same Width Then:

Diametral Pitch is proportional to z = 20 vs z = 16

The Lewis factor for z = 20 ≏ 0.320 (20 deg Involute) vs z = 16 ≏ 0.295

So:

z = 20 : Stress ∝ 20 / .320 = 62.5

z = 16 : Stress ∝ 16 / .295 = 54.2

IE: 15% more Stress in the gear with more teeth.

As I said below, the wear is greater on the gear with less teeth.

 

Hotgolf,

Thanks for chiming in, so it appears the "twin synchro" parts can be substituted for conventional oe or aftermarket synchro rings without machining or replacement other oe components - -

However, what's the "twin synchro" advantage? slicker, faster changes? easier to engage low and/or less crunch engaging second when cold? greater durability?

Regarding 020 upgrades, have you noticed differences in the cases dimensions such as the main and layshaft bearing support areas mentioned earlier in the thread?

While I've never calculated this, I've always assumed a fine threaded fastener possess a greater surface area than the coarse thread of a same diameter fastener, and that as with Daved's example of the transmission gears it has less material thickness through the root, which is where. all things considered, an over torqued fastener or overloaded gear most commonly fails