Can anyone tell me the difference if there is one ? Apart from the adjustable centre diff.
IS THE RATIO THE SAME ?

 

Errrm well.......
If the gearbox is from a type R or a Type RA then there is definately a difference, as these cars have shorter ratio's, plus the DCCD, now if your talking about a 4 door STi though.... im not sure as i dont have the ratio's for them

Tony

 

STi gearboxes of all types at least as far back as 1999 (I don't know about earlier than that never looked into it) are stronger than WRX gearboxes, with at least some gears having different gear tooth profiles and gear widths. New age STi gearboxes are also 6 rather than 5 gears. The 6 speed boxes weigh about 20-30kg more and are bulkier than the 5 speeds (requiring a shorter propshaft), but the case appears to be strongly braced and it has an oil pump. The ratios and diffs are invariably different as well. Not all six speeds have DCCD - most don't. A copy of DeltaDash demo (free download from ecutek.com) and bringing up the Road Dyno will let you see ratios, diffs and road speeds per gear/rev limit.

 

I have an Sti v3, and have tried an early RA box in it and the difference in gear ratios is very marked, so the difference of the RA/R to the WRX must be huge.
The RA gives killer short bust ratios but becomes very tiresome IMHO and the car is faster (in competition) with the Sti box.
The site www.Rallispec.com in the USA gives all the ratio comparisons.
I think it goes:
Tallest box = UK Turbo
WRX Classic
Sti classic
Type R
RA shortest.

DCCD does not affect the ratio cluster, just the drive bias from front to rear.

911

 

SO DO YOU THINK I WOULD BE BETTER PUTTING THE STI ONE IN RATHER THAN JUST THE SHORT SHIFT FROM IT AND CAN I TAKE THE CENTRE DIFF OFF AS THE STI ONE IS ADJUSTABLE .

 

SS:
Got your pm, but the 'normal' Sti does not have the dccd, only the Sti RA version and, I think, the Type R.
The WRX and straight RA have the same centre diff as the Sti.
The dccd is nice, but not to really die for. I would fit an Sti box and rear matching diff, a V3 or V4 box as the short shift is like a rifle bolt in action, very close gate, especially 2nd to 3rd. (in haste it is easy to go to 5th and not 3rd)
911

 

What year, model is your car?

 

THE CAR IS A WRX 93 BUT THE GEARBOX IS STI 555 MY97

 

I don't know much about the diffs in the earlier cars. Generally you will need to match the front and rear diffs, as the imports to my knowledge don't have 1.1:1 drop gears like some UK/Euro models. So you need to find out the diffs on the various donor/recipient models. 911 will probably be able to help you with this?

My swap was a MY04 STI UK box into a MY00 UK. Both have the 3.545 rear diffs with a 1.1:1 drop gear and 3.9 front diff, so with a shortened prop and new linkage it went straight in and the speedo is correct.

My upcoming swap is a 99/00 STI 5 speed into a 93 UK Legacy turbo. For this Pavlo has changed the drop gearing in the transfer case to 1.1:1, and changed the front CWP to 3.9 to match the Legacy (which happens to be the same diff values as the MY00 and MY04 above I already mentioned) and make it long geared to suit a 2.5.

It can be a hassle to swap rear diffs as they can be different sizes (R160, R180 etc) and then you end up changing the hubs, driveshafts etc.

 

What a mine field this all is!
I think that only the Jap imports (classic shape) had the 1:1 drop gears.
SS: Try searching for 'Stockcar' on this Snet and ask him, he always seems to know the right answer!
911