mk4 gear change

[Ess_Three]

I've read there are 2 different shaft(?) sizes on the 02j towers, not sure what they are but one is the same as 02a and one is different, so sometimes you will need to change the piece the shaft sits in inside the gearbox, but I've never seen this other sized one. could be the one you have maybe?

Found this pic, apparently the top one is 02j and bottom is 02a, but my mk4 tower off a 1.9 diesel I'm sure looks a lot more like the 02a than the 02j in this pic. It's got me wondering now though as I also read the 02a and 02j reverse light switches are different shapes but my 02j tower has the same plug as my old mk3 one 

Then you have another 02A tower...

02J is the top one...and very different.
for a complete 02J set up, you need the lot.

[Ess_Three]

is the code for gearbox marked on gear box somewhere?also how are the cables run on mk4,under car or through the body,as the mk4 im looking at at scrapyard is dumped on the floor with no wheels?

Mk4 runs like Mk3...under the body, above the exhaust, under a trip panel, that is in turn under a heatshield.

As for gearbox code - the 3 digit identification number is stamped on it somewhere...but as to whether it's 02A or 02J...look at the previous pic and suss it out.

The Diffs also vary - not the diff themselfes, but the way the drive plates mount to the diff to allow the driveshafts to mate up. I think 02A is circlip where 02J in cap head screw.
My 02A 'box had 02J drive flange mounting - from the factory!
Not that it makes any difference for bolting up driveshafts...but it does if you are fitting an LSD!

[tshirt2k]

Early mk4's have the same tower as a mk3 and isn't worth changing.

To change it all over, you need an 02j tower and shifter. Depending on your box, the tower may not fit into the bush in the bottom of the gearbox. When i changed mine it was a straight fit. Two bolts and some sealant and it was in.

The Mk4 shifter isnt a straight fit, but you can change the shifter housing to one from a polo tdi/ibiza 20v cupra and its easier. You can get these from dealer new. you do need the mk4 cables. shown here.





You can use any type early or late. The only difference is the bowden cable clips on the end of the cables. Early are ball type, later are held on with circlips. they are all interchangable though.

Early type



Late Type wont need buying if you go for the TT Short shift as they come on the short shift and the relay lever.

Late type Relay lever with catch 1J0 711 202 P



TT short shift 8N0 711 046

Mod required to fit MK3 mounting:


Checking it all works prior to ripping the old tat out the car:

You have to get under the car, take off the exhaust at the downpipe, and remove heatshield to change shifter and drill a hole like shown in the shifter housing to keep the front of it secure.

The shifter is alot tighter and shorter than the mk3 With the TT short shift, but because i rebuilt my tower with new parts and havent driven the car much, the shift is very stiff. But im told it does loosen up in time.

You also have to change wiring to reversing light switch so that reversing lights still work. its a different plug.

[Dan_GTi8v]

when you say the early mk4 tower is same as mk3 and isn't worth changing, do you mean it isn't worth changing towers at all or it just isn't worth changing from mk3 to early mk4?

also whats involved in changing the bush?

[tshirt2k]

when you say the early mk4 tower is same as mk3 and isn't worth changing, do you mean it isn't worth changing towers at all or it just isn't worth changing from mk3 to early mk4?

also whats involved in changing the bush?

Not worth changing at all because the only benefit could be that it was made a few years later.

what bush?   

look here for a rebuild thread.

click me

[Dan_GTi8v]

the bush the tower sits in in the gearbox

I'm still deciding whether to put in an 02s or not

[tshirt2k]

Its a bearing not a bush. And its awkward to fit. There is an easy way to remove it on CGTI.

02S isn't worth it as ratios arent good and you need to change bellhousing so you can have a speedo

[Dan_GTi8v]

Some others have told me the same things but I'm a bit confused as all the 02s box's I've looked at have taller ratios than the mk3 16v box I'm using atm, which is what I want to counter the silly torque I get from the 20vt. maybe I'm reading the charts wrong or something which is highly likely 

I'm not too worried about having to change bellhousings as long as its worth doing

[tshirt2k]

But they are oddly spaced and have short 1st gears. An 02A/J with a VR6 FD or go for lower diesel one would suit ya. The mk3 box has the lowest 1st gear available and a good set of ratios. A lower final drive should be good. I'm going down that route as i've done quite a bit of research on it in relation to my torque curve.

http://www.clubgti.com/forum/showthread.php?t=235941

At the moment a longer 5th will do me until i get my other box built.

[Dan_GTi8v]

I don't know nearly enough about gearboxs to understand even half of whats going on in that thread lol, what I basically want is to be able to drive normally without petrol bankrupting me but still have a bit of poke when some dick is up my arse on the m25    you think the mk3 diesel is the box I want?