simbo

hi thinking about puting a 6 speed box in my classis does the sti7 prop work or do i need to use the classic prop

cheers david

Tim W

iTrader: (1)

The Sti 6 speed prop from the new age car will fit straight on, failing that a classic auto prop will do the same job or you can get you existing prop shortened

simbo

cheers tim was thinking about shorting my own prop but if the sti one fits that mite be the better option.

but the rear diff does not fit does it ?

cheers david

Tim W

iTrader: (1)

That entirely depends on what your fitting the gearbox to. If you have a UK Classic and you're fitting a 6 speed from an Sti Type UK you don't need to change the rear diff. However if your fitting a JDM Sti 6 speed to a UK classic then you will need to source a 3.9 Crown Wheel and Pinion (from a classic Sport) for your diff, or look at fitting the complete differential from the donor car along with the half shafts, hubs and brakes.

However if you are fitting the gearbox to a classic STi 4, 5 or 6 then you could fit the new age car's diff

UK classics are fitted with with an R160 diff

Sti 4, 5 and 6 classics are fitted with R180 rear diffs and so are the new age Sti's

simbo

sorry my car is a 93 wrx and i am trying to get a uk 6 speed box

is the r180 a better diff to have?

cheers david

Tim W

iTrader: (1)

Off the top of my head I can't remember what size diff is fitted to your car, I expect it has a 4.444 ratio.

The cheapest solution is going to be fitting a UK 3.547 ratio diff and drive shafts (if your's aren't compatible) provided that your going to get a Type UK 6 speed box. But down side is that a UK diff has viscous LSD

Ideally you want a Surtrac (out of the P1 or the New Age Sti's) diff or a Quaiffe/Modena ATB diff

simbo

my diff is a 4.11 is it a viscus lsd?
what is the difference between a viscus and a surtrac/quaiffe diff
sorry about all the questions dont want to buy the wrong thing

cheers david

APIDavid

iTrader: (4)

You'll find that the centre support for the prop can be out of line on some 5 - 6 speed conversions. We had one in done elsewhere and the propline was like fiddlers elbow. Be sure to check that the driveline is as straight as it can possibly be. If needs be reposition the centre support bracket as you can't reposition the floor..............

David APi Engines / APi Impreza

simbo

so it might be better just getting my shaft shortened by 60mm then david?

cheers david

APIDavid

iTrader: (4)

Yours is definitely a 4.111 and it will be viscous assuming that hasn't been got at. The suretrak is only fitted to R180's. The only upgrade will be to a plated R160 type LSd usually found in STi cars You'll need to grind off a small amount of the inside of the diff casing to get it in. From memory it is one of the diff cover bolt, thread castings on the side of the main cast case that gets in the way. Quaife would be too aggressive for road use in my opinion.

Not really a job for an amateur. I don't mean that as derogatory, but it is a precision piece of work that you'd need to be confident about to tackle at home.

If you want a chat call me at the office Monday.

David APi Engines / APi Impreza

PS just seen your post. Shortening is an Ok option depending upon who does it of course........

APIDavid

iTrader: (4)

Just re-read this too.

Viscous is exactly that, a centre housing full of pressurised gloopy stuff that creates a resistance to turning against the inner parts of the diff. That's deliberately vague because if you try to take a viscous to bits the stuff squirts out all over and then all sort of small parts fall out. Never did figure out what went where.

A plated diff has a pair of cross shafts inside that have ramps on the cross piece. If you try to rotate one cross shaft against the other it rides up the ramp and exerts pressure against flat plates inside the casing. Some plates are anchored to the outer case and some are to the inner works. Thus a resitance is set up which increases as more pressure is set against the cross piece. It self perpetuates. The harder you try to turn it the harder it resists.

Does that make sense - sort of?

David APi

simbo

so does a plated diff change the way the car drives much or what is the advantage over the viscus

cheers david

APIDavid

iTrader: (4)

On a plated diff there is enough energy available to drive home with a busted drive shaft because the energy will transfer to the opposite wheel. A viscous will not do that. It has an amount of drive transfer when there is a resistance from both sides but when you remove half the resistance [ busted shaft ] the drive is lost - all of it.

Viscous is more road car friendly in operation. LSd's can tend to be noisy when the plates are working against one another. AND if the pressure against the plates is set tight before the ramps start to work, the car will hop and jump on tight full lock turns when the energy created is at its highest and both wheels, front or rear are trying to rotate at the same speed.

David APi

PS gotta be going soon may not be on here much more tonight.

Tim W

iTrader: (1)

David, I would disagree about the ATB (Automatic Torque Biasing) Torsen type differentials made by Quaife/Modena being too agressive for road use, they are actually more predictable in their behaviour than the plated diffs found in most Sti's.

Plated diffs are great on gravel and a bit 'snatchy' in their action on tarmac...of course it does depend entirely on how the ramp rates have been set up.

I'm certainly going to be on the look out for a Surtrac or Quaife ATB when the 6 speed goes into my car

simbo

well i do remember having a drive of a 300hp sti 5 and it seemed a lot more tail happy that my over 300 hp wrx which never really steps out is this because of the sti diff

david

Tim W

iTrader: (1)

Was it a 2 door type R, a 4 door V limited RA or just and ordinary 4 door?

Any car fitted with the DCCD active centre diff gearbox has a rear wheel drive bias, and they're certainly far more tail happy.

Suspension set up has an awful lot to do with it too though.

It's not so much that a plated diff will make the car more tail happy, it's just that when you eventually reach the point at which the LSD activates, because the torque transfer is spinning the inside wheel up, it tends to be a bit more agressive in the way it locks the diff and the break away can feel more sudden. A viscous or ATB diff will lock more progressively and as such it won't feel as snappy.

simbo

it was just a standard 4 door sti


cheers david