Sam's build thread

[sambb]

hmm I feel a hell of a lot better about doing this then. I may even get it in quicker than I'd initially intended. I spoke to Cmac engineering in Sydney and they said it wouldn't be too much trouble to take a crown wheel out from 113 to 114mm to match the Kaaz (assuming that I don't already have a 114mm ID crown wheel in the other box which is possible) and it shouldn't be more than 200 bucks. The alternative is to source a 114mm crownwheel and pinion separately. All the Polo Gti boxes have the same final drive but it may be that early Golf 02J boxes with the 114mm crown wheels will fit which would open up the chance to change final drive ratios but I haven't really looked into that. The rebuild kit for the diff from MD Spares in Melbourne was quoted at 450 bucks so that will be the next thing to get my hands on and then decide if the LSD rebuild is something I can tackle or if its a specialist job.

[Sydneykid]

Doing a service on KAAZ LSD is pretty simple, basically take out the old bits and put in the new bits. Just making absolutely sure that the new bits go in the same way as the old bits came out. The experience factor kicks in when adjustments are required, for example changing the orientation of the plates changes the locking action. Since it's a road car you don't want too much locking on overrun, otherwise it gets hard to turn at low speeds. So more 1.4 way than 1.6 way. That's where an expert can help you in determining the setting that is best for your driving.

Once you have it working as you want then future servicing is straight forward swaps.

Wear wise, we do around 3,500 race kilometers a year and the KAAZ LSD's need servicing at around 2 year intervals. I do check the data and can pretty quickly pick when the diff is allowing too much slip. Obviously that's not the same as road wear, plus we do change the oil every second race meeting.

Cheers
Gary

[sambb]

Here she is. Kaaz 1.5 way DBV1820 'Super Q' plate/clutch diff. My new shiny thing for the garage. Was great to meet Arno and his schmick little Mk 1 Golf. Its now being de commissioned back to street/historic plate duties which is why the Kaaz made way for a wavetrac and it ended up in my hot little hands. From what he said the proper LSD really elevated the car on the track compared to the torsens eg stability under braking and consistent drive under power rather than the torque switching around across the front of the car like the torsens do. For example we'd done more or less even times at Wakefield (low 10's, him a bit quicker) when he ran this diff, but at the Dub Nats when he ran the Wavetrac I think he said he was 7/10th off his previous times despite having new tyres and just didn't feel like he was there. So It'll be interesting to see if I can find chunks of time with it. While I'll have to up the ante with frequent gearbox oil changes, using the right amounts of friction modifier etc it does sound like the car will be sufficiently streetable with the diff so pretty keen to get the other box built up now.

[sambb]

In other news I'll be grabbing one if these soon. It's a fixed baffle insert that fits into the oem sump.

TSR 1.8t baffled sump insert

So a possible group buy could happen here. TSR don't normally post them this far for fear of them being damaged in transit. I've spoken to Brock (schalke04) who can get them here if a few are ordered together. So if anyone else is interested please let me know.

[simon k]

trick diffs are way cool to play with...

"no" on the baffle insert from me

[sambb]

No worries Simon. I'm all in on this gearbox now anyway. The sump isnt a panic.

On the gearbox front I dug out my spare set of driveshaft flanges to check that they fit the Kaaz and they do which is a sigh of relief so I'm pretty sure its the right diff for 02J/02A and our 02R. I spoke to the guy who built my current box and I'll have the box to him early next week for a tear down. Fingers crossed its already got a 114mm crown wheel. If not, some machining to do but no biggy. Once I know the diff will fit i'll order the LSD rebuild kit and I guess then we'll order the gearbox rebuild kit plus anything else it looks like we'll need eg synchros (think i'll do second gear as a matter of course), forks etc. This time i'll hang onto the diff that is removed. For instance Gripper diffs in the UK that make plate LSD's for all sorts of front drivers only needed an old diff as a template to be able to make up one for the Polo, so it could be useful for that sort of thing.

[sambb]

Ok I just went back through some emails with SQS I'd had a while ago when I was considering their 1 way plate diffs. One thing they said just caught my attention. Apparently VW went from the 114mm to 113mm crown wheel because they'd had problems with the rivets holding the diff onto the crown wheel failing. By going to the crown wheel with the 113mm internal diameter they were able to expand the mounting face of the rivets holding the diff against the crown wheel slightly in an attempt to overcome this. Seperately they said the 02R 113mm crown wheel has 12mm holes for theses rivets and the 02J 114mm crown wheel has 11.5mm holes. Now I just measured the shoulders on the bolts supplied with the Kaaz diff, and the bolt shoulders are 11.20mm. If it turns out that I have a 114mm ID crown wheel 11.20mm bolts into 11.50mm hole sounds alright but if its the 113mm with 12mm holes, that's pretty far from a close fit! Is that going to be ok if I machine the 113mm crown wheel into a 114mm and am therefore running the 12mm holes? Would I be better off just getting an 02J Golf crown wheel and pinion to be sure? SQS said and I quote "this is not big problem - it work"......'big' being the operative word - any degree of problem I'm not that cool with.
Can I have some opinions from people who know this kind of stuff. Yes theoretically at the correct torque setting this shouldn't be a problem but I like practical experience too. I have seen vids people have posted where diffs are moving on the crown wheel that are scaring me a tad.

[sambb]

In other news I found this VW racing site: VWMotorsport.info | Definitive information source for VWs in competition, worldwide Technical Documents , with various links to their race car prep, and here: http://www.vwmotorsport.info/vwtech/...J_overhaul.pdf , a link to 02J disassembly (very similar to our 02J).

[sambb]

this is a pic of my current box with the press fit bolts going down from the diff case into the crown wheel where nuts go on I assume. The Kaaz is different. The diff case (top) is threaded M fine, and the bolts (Kaaz provided) will come up from underneath and thread into it from below. Rivets are an interference fit, that's just how they work but my bolts will float within the crown wheel - problem?

[simon k]

Rivets are an interference fit, that's just how they work but my bolts will float within the crown wheel - problem?

nup, no problem with that... just so long as they're properly torqued

it's nice to have the bolts as a snug fit in the holes so the crownwheel is 100% centred, but it's no different to the way a flywheel is held on to the end of a crankshaft. There may be dowels but they're only there for alignment, the clamping force of the bolts holding the faces of the two parts together is what stops any movement

edit: I love gearboxes, the mix of precision parts and the way they withstand huge forces is incredible