I’m looking to do some research into possible ways to strengthen the 20VT gearbox. I have phoned up a few gearbox specialists but they suggest that I need to know where they are breaking first. Can I ask all members who have blown gearboxes to post:

1) Torque they were running
2) What part blew
3) Any pictures

I can pass this information on and hopefully come up with a possible solution/prototype that I would be willing to test.

Ooohh, you beat me to it!

Also, if anyone has any experinces of having fitted other gearboxes to the 20VT such as the Integrale etc.

oooo more money

Not yet its purley research first.

Off the top of my head, 6 spds die from lack of lubrication at prolonged speeds high speeds.

5spds, well you'll have to ask the likes of nyssa7 as he's probably broken a few.

Barbz also used to add a strengthening plate to his coupe. I don't know where is was fitted though.

I remember a picture of this being posted on the TI website, but wasn't it a 6 speed box, with a plate welded on to the end of the gearbox? (That is, Euro spec drivers side/UK passanger side)

The plate was for the early 5 spd as they were able to split. But i want to look it to other methods aswell as a plate alone can't be enough.

It would be worth trying to contact MWT from the forum. He is in Brazil and has the Fiat Marea with 547 f/lb of torque

His pictures are here, http://s2.photobucket.com/albums/y39/TETEUS/
and his contact information is here
http://www.online-presence.co.uk/_coupe/details.php?record=126

Engines yes - gearboxes, surprisingly not so! Not run a 5 speed other than the one which came with my original 20vt donor car, it broke on the rolling road but anyone's guess what condition it was in, so doesn't count

Have punched the diff through the bell housing with a 6 speed, but other than that, I think strengthening gearboxes to be a low priority unless you plan to drag race and side step clutches

So how is it your racing and only killed one box and other roads users have been through a few. I'm still on my OE box but if it blows I’m planning on something a little bit beefier.

because on a circuit there is far less load on a clutch than when doing 1/4's or launching on the road - as long as you shift smoothly.

maybe because Leighton has no mechanical sympathy

Oh look at that, another zero appeared on your bill

Seriously though, I don't drive my car too hard except on the track or the strip. Ironically the first box let go on the dyno (crown wheel & pinion) and the last two on the road when accelerating in 2nd (blown diff) and 3rd (blown 3rd).

The cost of strengthening a box is considerable, a lot more than you are thinking Jason. My last box cost me £220 fitted.

you mean its going to be £200 now instead of £20

I think I'm going to keep a look out for another 6 speed and keep it in my garage

i have blown two boxes in a year,first one i blew was in 4th and it was messy oil everywhere and there was a hole in the casing and the second one let go flooring it in second but that was the diff that time that went

Blew the diff in one box but mangaged to get away with fitting a second had diff and and diff case.

Seems like the diffs are very strong.

I question how often if ever the average coupe enthusiast changes his gear box oil.

With a helicial gear the thrust forces are a lot greater then a straight cut gear (hence greater power loss)this can force the drives sideways reducing contact or rather leading to an uneven wear. High torque simply forces the shafts apart. In Bowen's book on gearbox building he mentions the addition of extra webs to OE castings as a method to keep the shafts in mesh, would need a very good welder and machined sections.

If you want to know then ask someone who had to go all out-http://www.jmcpower.com/ , Mike is the owner.

rich

maybe I change gear smoother? Not being clever or derogatory - certainly I don't bother with heel and toe crap when driving a road car, but have a good bash at matching revs on downchanges far more diligently on track. Puts it under less strain and less likely to lock the fronts changing down

we also do rolling starts in the LMA Euro Saloons so no giving the box grief from a standing start. Have done a couple of standing start races in the DMN series but I'm going to get so much wheelspin anyway, just get the thing rolling gently and then boot it. Any one who saw me pulling away at Santa Pod two or three years back - I got it rolling like I was towing a caravan, then hoofed up the strip with the wheels still spinning in 5th. Strangely, it wasn't long after that the diff went through the bell housing smashing all the casing. But still using the same gear set in a new case

Besides, I've made up in engines what I've saved in gearboxes ;-(

could you strengthen the 5 speed n/a box so it could take the torque of the turbo

You have to start with the basics!

There are 3 different 20VT gearboxes, so which one are you asking for?

The early 20VT box IS the grale box but with a different housing (maybe only bell housing)

The late 5 and 6 speeders are very similar with the obvious difference.
The whole linkage is different so in changing box between new and old style you also need to change the linkage


My opinion is that the number one problem is the OE gearbox oil is a pile of cr*p. In fact in response to 6 speed failures you will find that Fiat changed the recommended oil. Likewise what Rich said about changing the oil. I have had my gearbox oil changed regularly

I have never used the OE oil and in general my boxes have lasted better than expected. At 400BHP & 400lbs/ft I did about 25,000 miles and at 350BHP & 360lbs/ft for 20,000 miles+ all on one 6 speed gearbox. That box died about 3 days after I got 560BHP and the subsequent late 5 speed I had lasted only a short time. That might be because I was trying a very high viscocity oil. My current box has done about 2000 miles I think and is another late 6 speed.


I have 3 6 speeders and 1x 5 speeder in my garage all broken. On the 6 speeders one lost 3rd, one has the whole lay shaft moved, one had the rear bearing burn out. I think only one of the casings remain intact
The 5 speeder I'm not sure what happened to it

It will get increasingly difficult to find low mileage boxes that themselves aren't already worn.

Like flea I have a local mechanic who can swap them quickly and charged me only a couple of hours labour, and my box was also cheap.

Didn't you crack a gearbox on a pothole once John?

Some good info their John. I have always used proper gearbox oil. Do you have any pics of your broken boxes?

Yes, thanks for that John. I have always been very carefull to change the gearbox oil regularly. I use the fully synthetic oil that was recommended by Oilman.

In fact Jason, you should have a spare bottle of that oil that Roger at Powerfiat gave you....

yes good memory!

My car bottomed out on a major dip and rise in the road and broke 4th gear I think. That was another box again - a late 5 speeder.

Good point on the oil John, needless to say I'm not using stock gearbox oil either. As best as I recall, we're using Joe Gibbs synthetic that AAOil supply - its where I buy the fuel from so comes on the same delivery truck

wow...a dip and rise did that?!!?

fccuk me running...

yup, don't underestimate the oil, I'm oddly enuf using a 75/110 or likewise Joe Gibbs oil ( with a good bit of guidance from JohnS ).

It's very pricey, however seems to be keeping it all tip top at present : I must admit, with the gearbox cooler up & running, you can actually hear it humming away in trafic when coming off the motorway, so it does get hot.

Oddly enuf I checked it a while ago & there is NO hint of discolouration, where as with the new box I had fitted, after 1k, the oil was quite silvery :o, so it just isn't protecting

1) 74kgfm @ 6000rpm

2) 5x Diff and 3x 3rd gear (5 speed gearbox)

3) Pics:
http://i2.photobucket.com/albums/y39/TETEUS/Variados/11-08-08_2201.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/11-08-08_2203.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/11-08-08_2141.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/11-08-08_2105.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/11-08-08_2101.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/11-08-08_2100.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/11-08-08_1526.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/quebranitro.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/quebranitro1.jpg
http://i2.photobucket.com/albums/y39/TETEUS/Variados/quebra31.jpg

The original Gearbox supports up to + or - 60kgfm torque, above that I had problems with 3rd gear and diff, the diff broke 5x and 3x the 3rd gear, then i decided to make a straight cut Gearbox and LSD diff, never more broken.

I use Motul 300V.

http://i2.photobucket.com/albums/y39/TETEUS/MWT%20STAGE%203/28-08-08_1607.jpg
http://i2.photobucket.com/albums/y39/TETEUS/MWT%20STAGE%203/28-08-08_1657.jpg
http://i2.photobucket.com/albums/y39/TETEUS/MWT%20STAGE%203/30-08-08_1632.jpg
http://i2.photobucket.com/albums/y39/TETEUS/MWT%20STAGE%203/30-08-08_1605.jpg
http://i2.photobucket.com/albums/y39/TETEUS/MWT%20STAGE%203/30-08-08_1606.jpg

Cheers,
Mathew

Matt you have spent some serious money on that car. What was the origin of the straight cut gear kit, was is a Brazilian product or one of the Euro gear sets. I assume it to be dog engagement.

Rich

Excellent post exactly what i was loooking for.
I'm intrested in that gearkit. How much did it cost?

Yes, the kit was made here in Brazil, was developed specifically because too there are no kits "ready" for that gearbox here in Brazil.

No dog engagement, is synchromesh, because I use the car on the street and also for rides.


I paid U$3500, I believe the value is high because the kit has been custom.

Mathew.

So this is an old trait of yours eh Flea?

It doesn't look like strengthening the gearboxes has made any headway since this thread was started in 2009.

Boxes keep failing in the same way, but I guess it's because no one is prepared to spend the necessary funds for a good strengthened gearbox.

Pero,patience.Mine is currently under testing.3 trackdays 1/4 mile day and 2 mapping sessions= some road abuse with no issues.

Can anyone help me with JohnS's post above ?

I'm interested to know how the two 5 speed boxes (Early and Late versions) can be identified ?

Apart from the Quaife, have you done anything else?

My box lasted a whole couple of hundred miles.

Erm have you seen what lenths Sparco has gone to with his gearbox

Yes and i think the poor chaps still having issues.

What we all want here is a cheap fix thats reliable and with little modifications.
So unless your willing to spend circa £1500 like me then theres no point in continuing to advise on this.
There is no cheap fix other than throwing boxes in the cars at £50 a time.

Yes John, I think you are correct. In my opinion i think that after 450hp the gearbox options are limited.
450 hp and more investment into brakeing and handleing is in my opinion going to achieve a well balanced track coupe.

I do realise that there will be faster coupes on track easily.
But for an all round every day reliable fast track coupe that can be used year in year out is a 450 hp coupe.
I do realise i am not the best informed but it is just my opinion.

Thanks Joe,
can we clarify here how many people have blown there boxes up around a track?
I have got through 9 and i am on my 10th.Not one has gone on the track (Thank god)
So the undulations in the road play a contributing factor to the issues that have arisen.
1/4 miles dont count

I only killed mine with a full-throttle launch at Santa Pod - broke the planet gears in the diff, which then broke the diff and pushed it through the casing

I agree with magooagain - 450bhp is enough - I won't be going for any more (other than mild tweaks via a remap when I get bigger injectors). It's ultra-reliable, and I can use a Helix Organic clutch (which means I can drive it in traffic).

Yes, I'd love 500+, but I will not accept the compromises that come with it (lag, driveability, traction and of course, broken gearboxes).

Yes, I know a 2.4 would reverse some of the downsides, but I'm not in a position (yet) to splash the cash.

What did Sparco end up doing in the end? I know he spent a huge amount on his gearbox

i cant remember what he did but i know it was a complete custom billet box?

i think thats what he used any way...

I hope he doesn't mind me saying, but it wasn't enough. The casing still gave way.

Ross

Maybe we've found the reliable upper limit of Coupe tuning. TBH, it's testament to the basic engineering that the stock gearbox can happily take double the stock power

Nearly triple on mine soon i hope

That said i have known a few coupes blow boxes on stock power.

Has nobody offered up different gearboxes?

Mounting plates can be made up very easily if one was a close enough fit.

£8.5k and counting guys but that's a full billet steel dog kit i the standard housing which i get the feeling is going to be looked at and possible a new stronger end casing manufactured. This tuning lark is fun isn't it!!!!!!!!!

Just on the gearbox?!!!

Yes and that's me supplying the casings so far too!!!!

Yes £5800 for the full custom dog kit.

First failure after 50 laps was a selector fork which when it broke tried to allow the gearbox to select2nd and 3rd at the same time. The re-made the selector frok from Billet along with a few shafts etc and the repair bill was £2800

Box lasted 4 laps this time and as it stands i'm awaiting analysis on what went wrong. It does look like i will be looking to strengthen the casing in some form though regardless as when the dog kit is working it works very well indeed.

Oh and that's with my own gripper plate diff in it too not and Elite one.

Having this sort of stuff ain't cheap but pioneering stuff for the coupe never is as youwell know and people like Barbz, John S and Taz.

When my car can go toe to toe with a 400bhp factory Porsche GT3 cup car then it's very rewarding and all the hassles and hiccups seem a lot more worth the effort.

Bearing in mind i'm only running 450bhp and not huge BHP like some road coupes.

What is killing your gearbox then? I'm running the same power and I'm not breaking them (although I tend not to jump over saw-tooth kerbs at full throttle on my daily commute...)

Are you being particularly brutal with it?

Nigel, have you ever seen Marco in action

Brutal is on his warm up

You could buy a lot of £50 gearboxes for £8.5k!

Surely its shock-load that's breaking the 'boxes - once rolling, they appear to be capable of holding huge power.

I have to admit that I've heard a couple of worrying thuds and clunks from my 'box, usually when one wheel spins up and grips again (such as over a drain cover in the wet)

I could imagine a 'box in race use would get similar sudden loads as grip drops and returns, although a slippy-diff should lessen the effect.

Dumping the clutch is a bit brutal on a gearbox, but it usually results in loss of grip, especially when delivering 450bhp through the front wheels. Its only if the tyres grip hard that the load is high.

I am still surprised that the box can take 400BHP plus with seemingly no issues...

Not in my case. Third gear stripped on mine after I was well on my way out of a bend.

It looks like it just couldn't handle the torque.

On my first coupe (3rd gear box) I ripped the end casing off in 4th at around 90 dropped the oil over the rear wheel. Was a scarey momment I can tell you.

The failures i have seen down the years have all been to do with the diff or casing.
With 400 BHP on the stock late style box i could pop the diff out every time on a hard right hand bend in 3rd gear .

You see the same rotational marks on the diff casing.
The casing failures are also due to oil starvation and this is noticable on the 5th-6th gear end bearing.

casing failures again are also due to the planet gears fracturing and locking up.
Typical symptoms are locking into gear until the car cools down.
If the planets fail then it will push the diff crown wheel and the secondary shaft apart causing the weakest link which is the casings to shatter.

I am yet to break a box on track which would suggest that the wear to the box plays a big part whan the diff is challenged by undulations in the road surface which you dont get on track.
Also the track offers a much increased transfer of heat into the oil whereas the road doesnt.Thicker oil ie when cold is a contributing factor also.

Biggenz in your case you run the early box which is renouned for having issues with gears under extreme torque or boost.
The grale forum was littered with the same issues at one point.And your box is near identical to the grale boxes.
The later boxes have a much stronger gearset which you can see with the difference in colour between the early and late boxes.
The ''Myth'' that the early type boxes are stronger in my opinion is just that.
The casings are much denser in colour which would suggest that they were made from a different material than the later types.
I havent got 2k or more to spend on boxes so with a spanner and candle light i take the time to address the failures and hopefully it will not find another weak point.

So far i had more probs running 400bhp with boxes than running nearly 600bhp and 500ibsft torque.

So you're saying I gave up my 6 speed box for nothing?

From my understanding, it was to do with the way 3rd gear is created. Something to do with the 2 parts being tack welded together. When they go, the 'grale lot get a coupe 3rd gear as the construction of the gear is different.

No in your case when your running 2.1bar with a 8500 limiter you would kill any box.
High boost hero's.Be wary.

Sadly I'm only running 2bar@8250rpm to keep things a bit safer.

It's not that i am being particularly brutal with the gearbox Nigel. I am seeing different problems than anyone on here will have seen purely and simply because my gearsets are completely different, in both size and make-up. It brings with it new problems which have manifested themselves in Elite Racing Transmissions eyes as showing the weakness of the OE casing. Now i don't completely disagree that the casing might be a weak point in the whole set-up but both my failures i feel do not point to just a plain casing failure. I won't go on a rant until i have finished my negotiations with Elite on a solution but suffice to say if i am to continue running the dog kit as is then i think we will have to look at either a new end casing altogether or a radically strengthened one. The diff side is not a problem as it's a plate diff and has not given us any problems so far. I will keep you updated as to my progress.

An interesting point i have here is that i only run 1.7 bar at 450 bhp with just over 400 lbs ft so not mega boost.