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Front diff interchangeability: The true answer


WJM
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Just swap the ring gear over.

 

As for years for STi 5MTs...I do not know the answer.

 

Some have VLSD, some have Helical, others are rumored to have a clutch type.

 

Any year STi with a 5MT. the 6MT diff will NOT work. I have tried.

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its just the front diff its self...the actuall differential.

 

No parts other than the diff its self need to be swapped.

 

You can order aftermarket, or get an OE STi 5spd front LSD from SUBARU-STi.

 

There is a rather lengthy thread on Nasioc, about the OBX front quaife style front LSD, which should fit, as you say. But what is the spline count, on the WRX and do you know if this is the EA style stub axle or is it a male C ring style of the newer ones?

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The turbo MT stubs are 25 spline...and OMG!!!!!!!!!!! 95% of all the EJ stuff with stubs (up to the 11/2003 production date, which means the middle of the 04 model year) are 25 spline.

 

Direct fit.

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The turbo MT stubs are 25 spline...and OMG!!!!!!!!!!! 95% of all the EJ stuff with stubs (up to the 11/2003 production date, which means the middle of the 04 model year) are 25 spline.

 

Direct fit.

 

yes, but the newer cars use a different style stub axle, will that work in the EA box? or do you need to use the EA stubs....will that even work?

 

that's something I hadn't thought about. I wanted to use this in my lifted rig, and just assumed you'd use the same stub shafts. but it sounds like that may not be the case.

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Numbchux: They are the same....unless you are refering to the post 11/2003 cars that have stubless diffs, the axles slide INTO the diff. Then there is STILL NO PROBLEM as 99% of the aftermarket diffs out there are for the stubbed diffs. Either way, if you get one thats stubless, order the stubs from an early diff, and insert them. Done.

 

Noah88DL: Use turbo axles. Done.

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Numbchux: They are the same....unless you are refering to the post 11/2003 cars that have stubless diffs, the axles slide INTO the diff. Then there is STILL NO PROBLEM as 99% of the aftermarket diffs out there are for the stubbed diffs. Either way, if you get one thats stubless, order the stubs from an early diff, and insert them. Done

 

not reffering to the later stubless ones....just EJ vs EA. turbo axles are pretty hard to come by around here, is it possible to use the EA82 23-spline stubs in the LSD? or do you have to use the EJ stubs?

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XT6 is the same.

 

Well...you might could get something custom machined...

 

Try it.

 

I imagine that the stubs that would need to be used would need to be the ones that came in the diff...aka the ones for the 25 spline EA and all EJ. (Same part number)

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WJM - From what car you got the front LSD?

What type of LSD does it have?

What's the differences between those types of LSD?

 

None specific....I ordered an aftermarket unit, the OBX Helical.

Its a Helical, a torque biasing worm gear operated diff.

 

Clutch: Has static and dynamic resistance, even with one wheel comepletely unloaded. Best for most types of racing.

 

Planetary/Helical/TQ biasing/ATB-Quaife/SureTrac Cam type: Usually operates only under acceleration, and BOTH wheels must have contact with the surface. Any complete loss of traction on one wheel means the diff doesnt work. These diffs work with the wheel speed differential to create LSD action. These types of diffs are best on smooth-sealed surfaces and street cars....and other applications where clutch types are not highly needed.

 

Viscous: These diffs only work when slip is created. Similar to clutch type, but have almost no initial load. Once slip is created, fluid between the clutch plates heat up, creating the LSD action. These are best used as the center or transfer case diff on AWD cars, also found in many rear diffs....sometimes found in the front of FWD cars, but rarely. These diffs are best for normal street cars that may see adverse conditions. Very quiet and stealthy operation.

 

Active: Most comonly these are planetary/helical units with electromagnetically operated clutch packs that control slip action. These diffs are most expensive and need electronic or other typed of input/information to operate properly. Under normal use, they act as any other planetary or helical diff. As slip is created and conditions change, depending on programming, the clutch packs are activated, limiting the slip (say, if a wheel looses complete traction) therefor keeping maximum grip. These are commonly found in the Version 8 and later SUBARU Impreza WRX-STi with the 6MT, it is the center diff setup. Also found in the Mitsubishi Lancer Version 8.5 and MR version. NOT found on the RS version until 2005, IIRC.

 

Thats it...I think.

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None. You need to weld your diff for off-road.

 

just not true, welded is best, but you certainly don't NEED to weld it. and welding the front would be just downright dumb! clutch-type LSDs are a big step up over open, not as good as welded for the hardcore wheeler, but for most people's use, an LSD is fine.

 

helical's are useless offroad.

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clutch-type LSDs are a big step up over open, not as good as welded for the hardcore wheeler, but for most people's use, an LSD is fine.

 

helical's are useless offroad.

 

Well - the small R160 LSD clutch pack is just too small for the large tire sizes, and relatively slow speeds of trail use. The small amount of help the LSD provides isn't worth the cost of finding one. For the price, you could almost BUY a welder and do the welding yourself on the rear diff.

 

GD

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  • 2 weeks later...
My OBX helical front diff is here.....now to install it.

woah woah woah.... helical???? I didnt read all of this but are we talking that were able to put helicals in like my GL-10???? Plus if not now... mabey in the future since im thinking of swapping an EJ25 into my roo??????

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