It had all been going so well with the Octavia RS project. With what seemed like only a few things left to do to get it up to par.
Quick Links – Why? – How – Finding a ‘box – Fitting – First Drive – Mistake?
And then it happened.
Driving along in fifth gear, minding my own business and ****BANG!!!!****. An explosion from the gearbox area which sounded like something had snapped in the biggest possible way.
The car limped back to base making expensive noises but with no signs of damage. Externally. No oil leaks, no gearbox oil sprayed everywhere, nothing. Just a horrible noise if the car moved.
A bit of research later and it turns out the 02J gearbox has a fatal design flaw with the differential. A tiny metal pin can snap and when it does it takes the gearbox case with it.
And that’s what happened to me. Except the gearbox case seems to have survived.
What To Do?
Fortunately the gentleman that detailed the flaw with the 02J gearboxes also gives a solution. The 02S 6 speed gearbox is a more or less a straight swap for the 02J. When I heard that, there was only one solution. We were doing a six speed conversion.
Why 6-Speed?
02J petrol gearboxes cost around the same as an 02S gearbox. Except the 02S gearboxes are much younger and therefore probably have much less miles on them.
An 02S probably won’t have the same design flaw as the 02J (If I was fitting an 02J I’d want to open the box to fix than pin problem with the diff which adds to the cost).
And being a newer design you’d think VW/Audi would have made some improvements to the box over time.
As it turns out, I managed to find an 02S gearbox for much less than the price of an 02J. I guess there isn’t any demand for the 02S gearboxes. Which is always a good sign.
Choosing a Box
Click the picture on this page and download the gear ratio Excel spreadsheet. It’s what I used to choose the gearbox code, but double check the ratios with another source to be sure the data is correct.
The 02S comes in loads of different cars but the ratios aren’t that different.
There is a 6 speed used in TSI motors. This has a shorter first than the 02J and 6th starts where 5th ends on the 02J. I didn’t like this. The gears in the 02J were far apart already, really at the limit of what I wanted. If first was shorter, the gap between the other gears would be bigger than the 02J gearbox.
There is the diesel box which I didn’t go for.
And then there is the 02S for normally aspirated cars. In these boxes 6th is a tiny bit longer than 5th in the 02J box and first is a bit shorter. In eh, short, the FSI box was a close ratio box for a turbo motor. Maybe a slightly longer final drive would be nice but it will do.
Ebay
Looking on ebay using the codes of the gearboxes I was after, yielded a result. 2 weeks later I was in the possession of a sorry looking 02S box. Fortunately some engine degreaser had it looking like new. Twisting the driveshaft cups and input shafts everything seemed fine. No grinding detected and it seemed to go in all the gears.
Fitting – 1.8T 6 Speed Swap
With the box sourced, next step was to get it fitted.
It is a direct swap but some things needed changing.
Driveshaft cups needed to be swapped between boxes. The 02S uses smaller diameter cups.
The dogbone mount needed a new mount drilling in the gearbox case.
And the MK4 gear selector cable bracket needs to be used on the 02S with two custom brackets.
Shift weight from 02J bolts on to 02S.
Finally the dash needs to be programmed to take speed from the ABS sensor instead of the VSS sensor (which the 02S does not have)
And that’s it for the 1.8T 6 speed swap. Literally.
First Drive
After filling up with gas, trying to pull away, I thought it wouldn’t go into first gear. Locked out, no movement. And then I realised, it was in gear. It’s just that it moves so little from the centre it seemed it couldn’t be in gear.
Honestly, shifts could be a bit of struggle with the 02J, not so with the 02S. Throw is much shorter forwards and back, now it’s like a light switch. You press, it goes in.
I didn’t imagine that the feel of a shifter could affect the way I feel about a car so much.
Before I liked the “old skool” driving experience and put the less than precise gearshift down to a characteristic, something to be savoured. Ten minutes into the first drive with the 02S it felt like I was driving a different car. The car all of a sudden seemed brand new. New as in a rental car from National Car Rental. Absolutely amazing.
Again, who knew that the quality of the shift could have such an affect on the way I perceived the car. Incredible.
The Ratios
This may have been a problem if shifting gears was slow. But it isn’t. So having to throw gears at it, is a pleasure not a chore.
It’s still early days but getting it moving from a standstill is nicer, I don’t have to ride the clutch so much. And the gears seem perfectly and evenly spaced. It’s great. Really great. I might get board of the shifting at some point, but at the moment it’s fun.
What Have I Done?
The car is completely transformed in a good way. It is literally like a new car.
I thought there might be a slight improvement with shift quality but the difference is night and day.
I thought it might be worse having six speeds but it isn’t. It’s great having more flexibility at 100-120km/h. Fourth might have been a bit too short before, fifth a bit long. Now fifth and sixth are completely usable.
In short, I can’t recommend doing this enough. Especially if you haven’t had your 02J differential preemptively fixed. In my experience it’s a ticking time bomb. The fact the cost of going to the 02S is close to putting in another 02J in, the 1.8T 6 speed swap is a no brainer.
Just check that excel file I linked to above to make sure you get the right code. Think what you like and don’t like with the box you have now, ratios wise, and choose accordingly.