pilotafactory

I've bought a 6s sti non-dccd conversion kit for my classic, from a reputable seller here on the forum... kit was made by box coming off a 2003 wrx sti ( viscous center diff) , propshaft, and a r160 with the matching (3.9) gear ratio...

Installed all this in my classic, from the first meters of use I noticed little clunking binding from the rear of the car when doing reverse manouvers , thought it was normal ... maybe this box and rear diff have more lock % than my old ones, i thought !

Using the car further the issue became more noticiable, until my first time at the track: after I went out of the track, car very heated, I parked the car wile steering locked and the transmission suddenly locked up with bad clunking noise!
But very weird thing happens at the same time: the gearstick lever gets kinda seized : car was in 1° gear, and the stick was very hard to get in neutral, and once in neutral it was always very hard to move, like it was glued !

After letting the car cooling down a while I started it with the front wheels straight and both transmission and gearstick got free again!

In the next days I noticed this problem also in every day use, when the car is warmed up, until today when I went again to the track and it did the same thing every time I stepped of the track with the car being hot !

The clunking , binding and locking are clearly a sign of a failed center diff, but is the seized gear stick related to this?? I mean , the gearbox works flawlessly even at the track, but the lever suddenly gets stuck when the locking occurs ... what do you think?

Is it possible that the differential that has been sold me is not the correct gear ratio and causes the problem? I believe not, because if so it should clunk and act funny even in a straight line and not only with while steered at slow speeds...

Infected by sti

iTrader: (6)

If it's a UK Sti 6 speed box then it won't have a 3.9 final drive, the 3.9 final drive is only found on the shorter ratio jdm boxes from my understanding, I could be wrong but when I was sourcing one for the rear of my 2003 jdm blob Sti I could find many uk 3.54 and 4.44 final drive but not so many 3.9 and when I asked the question the way I understood it was the 3.9 only came on the jdm cars, so if your running a uk 6 speed with a rear 3.9 diff then perhaps that's where your clunking and banging is coming from as the wheels would be trying to turn at different ratios.

Its just a thought, I'm no expert with gearing mind

pilotafactory

thanks buddy but I don't think so, at least according to this : http://www.gearhack.com/myink/ViewPa...ission%20Chart

my gearbox is the last of the 6 speed list, code TY856WN3CA , hence uk model 3.9 final drive... BUT maybe the rear diff I've buyed coupled to the box is not 3.9, who knows ! I took it and placed it in the car without even looking at it...

Infected by sti

iTrader: (6)

All the 6 speed boxes have a front diff ratio of 3.9 But AFAIK in uk/euro gearboxes there is final reduction of 1.1:1 before to go on the rear axle shaft, so 3.9/1.1 = 3.545 where as the jdm box has a 1:1 drop gear which equates to 3.9 final drive, so if your thinking along the lines of the 3.9 front diff on the box then they are all the same as far as I'm aware but its the drop gears that make the difference in the ratio, so if you have a uk 6 speed box you need a 3.54 final drive not a 3.9 if that's what you have installed. It had me baffled for ages when trying to work out what was what with them but that's how I was explained it like I say I'm not that switched on with gearing but I just seen the 3.9 rear diff bit of the post and if its a uk box then my understanding of it was its the wrong ratio, please excuse me if I sound thick

pilotafactory

you're right I've forgot about that !! anyway I've exposed the problem to who sold me the gearbox and probably he guessed the problem: he sold me the matching rear diff with 2 rear axles, but my garage leaved fitted the old axles instead of the new ones because one of them had a seized wheel bearing ... and the axles look identical but actually they have some minor differences that could be causing the clunking !! this would cause the center diff to overheat, the gearbox itself to overheat and hence the sticky gear lever....
I hope he is right, I'll be swapping the axles asap !

legacy_gtb

iTrader: (3)

If its got that hot, the silicone oil in the viscous centre diff is probably fubar'd bud.

pilotafactory

I know, thats what I fear.... anyway I will try changing the axles and the gearbox oil ... I currently have motul motylgear 75w90 wich is very thin, i will try putting in something thicker that should cope better with the heat... I'll see how it goes and in the case I will search a new center diff