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Old 10-20-2009, 07:18 PM   #1
coldturbo
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Default 80's MLSD in modern R160 housing

I need info about using a late 80's clutch type LSD carrier in a 02 WRX R160 housing.
My question is this: I know that they are both R160 and will pop in with just a ring gear swap but what about the axles?
Will the LSD carrier spider gears mate with the male WRX axles?
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Old 10-21-2009, 10:09 AM   #2
AndrewtechAutomotive
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Lol, do you want to use the clutch diff our of an old XT or something?

I'm sure it'd work alright. I think the Legacy Turbo LSD axles fit the LSD WRX R160, and I am also pretty sure the Legacy Turbo LSD axles fit the old clutch-type.

The question is... why?

Your current 02 R160 has a VLSD. You'd be trading a weak VLSD for a 20 year old (minimum) clutch-type LSD. Even with new clutches, your car makes more than double the power of the older cars. What do you intend to gain by using one of those diffs?

Phil
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Old 10-21-2009, 11:37 PM   #3
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What is the force transferred across a vlsd? The old skool clutch type has a breakway torque of 150lbs/ft at the axle nut. Adding a 1mm shim behind the spring washers will bring that breakway torque up to 200-ish. Much-much more than the vlsd, so corner speeds are greatly increased.....even with a wheel up in the air.

Weakspots? The stubshafts are hollow......but replacements can be sourced too. The axles are not as big as later Impreza type. One would have to cobble together parts to make one stronger (if it's even possible).

We've been extremely happy with ours....for years!

Jay
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Old 10-22-2009, 02:07 AM   #4
coldturbo
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Quote:
Originally Posted by Storm View Post
What is the force transferred across a vlsd? The old skool clutch type has a breakway torque of 150lbs/ft at the axle nut. Adding a 1mm shim behind the spring washers will bring that breakway torque up to 200-ish. Much-much more than the vlsd, so corner speeds are greatly increased.....even with a wheel up in the air.

Weakspots? The stubshafts are hollow......but replacements can be sourced too. The axles are not as big as later Impreza type. One would have to cobble together parts to make one stronger (if it's even possible).

We've been extremely happy with ours....for years!

Jay
Thanks for the input.
To answer the question. Grip in the last 2/3 of a corner.

It looks like I need axle stubs from a 90-94 Legacy and the Legacy half-shafts.
The track is close, 67.1" in the legacy and 68.1 on the WRX so that is 0.5" per side.
I don' t know how or if they can be combined.
Any other ideas?
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Old 10-22-2009, 07:34 AM   #5
AndrewtechAutomotive
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Quote:
Originally Posted by Storm View Post
What is the force transferred across a vlsd? The old skool clutch type has a breakway torque of 150lbs/ft at the axle nut. Adding a 1mm shim behind the spring washers will bring that breakway torque up to 200-ish. Much-much more than the vlsd, so corner speeds are greatly increased.....even with a wheel up in the air.

Weakspots? The stubshafts are hollow......but replacements can be sourced too. The axles are not as big as later Impreza type. One would have to cobble together parts to make one stronger (if it's even possible).

We've been extremely happy with ours....for years!

Jay
You can't rate a VLSD like that. Viscous LSD's are based on a shear thickening fluid. As shear occurs, the fluid becomes more viscous, and torque transmitted through it varies as needed. The upper bound practically infinite, and limited only by design. At the upper limit of shear, I would imagine you could see torque transmission in the 175 to 190 ft-lb range.

How are you rating the 150ft-lbs on the older diff? And weren't the old diffs a 1-way?

I'd rather spend the money and buy a KAAZ or Cusco. Proven time and time again to be reliable. Plus, they aren't 20 years old, and they use the axles you already have.

Phil
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Old 10-22-2009, 08:34 AM   #6
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Good points about the age and proven track record. However, the old skool units also have a proven track record in the wacky off-road world, and they've been workinggreat fo us.......admittedly, we don't make nearly the power that even a mildly tuned WRX would make.

I understand the difficulty in trying to directly compare the shear forces of the viscous unit, as it's not designed to function the same way. It is well known that they are virtually worthless for higher performance driving than many of us do.

I simply put a torque wrench on the axle nut to see how much force it would hold before slipping. Probably not the correct way to measure it, but it's repeatable for me to quickly check if the diff is getting weak.

They are 2 way by design. Here's a couple pics of the spider gears and pressure rings.



The known weakspot are these hollow stubshafts.



Axles are a bit spindly....clearly not meant for big power. Only meant to get a lightweight 4WD vehicle where it needs to go, with a real locking transfer case helping by forcing the front end to take on it's share of the work.



Coldturbo: I'm not sure if the axle lengths will work out for you. .5" is alot when you're looking at the job the CV and DOJ has to do.

This diff isn't superior to the units out there these days, but I believe they are a viable option. I may have to go with something different if I build the car to make higher power and torque. Until then, I'll stick with this cheap option that works.

Jay
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Old 10-22-2009, 09:47 AM   #7
AndrewtechAutomotive
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The axles should work. There are many a person running WRX control arms and lateral links with stock Legacy axles. The issue becomes less severe as ride height (and CV Misalignment angles) decrease.

What car is that in Jay? You said wacky off-road world, and not a lot of power. So I imagine an N/A and for low-grip surfaces, not remotely close to the loading seen with an "aggressive" street driven car. Even on their best days, an N/A will barely make stock WRX power.

If you want to try, by all means go for it. But I wouldn't get your hopes up too high.

Phil
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Old 10-22-2009, 11:59 AM   #8
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Quote:
Originally Posted by AndrewtechAutomotive View Post
The axles should work. There are many a person running WRX control arms and lateral links with stock Legacy axles. The issue becomes less severe as ride height (and CV Misalignment angles) decrease.
Yes, this is true. I would try it, expecting it to not be quite right and hoping it would work out fine with the car lowered.

Quote:
What car is that in Jay?
I'm running one in a 96 Brighton with some engine work and alot of wheel, tire and suspension work. I run another on in a 98RS with the same amount of work done. Our avg. autocross times are quicker than most (if not many) WRX, so it's not like we're just putting around without a turbo.

Quote:
You said wacky off-road world, and not a lot of power. So I imagine an N/A and for low-grip surfaces, not remotely close to the loading seen with an "aggressive" street driven car. Even on their best days, an N/A will barely make stock WRX power.
The wacky off-roaders would be in the old skool scoobs running big mudder tires on the Loyale, Brat, and variants of them. Sick offroad rigs being put through stress I would put beyond what I'd do on a typical autocross course. Crawling and mudding still exert alot of drivetrain stress when the overall diameter of the wheel/tire combo is much greater than what we typically run on tarmac. With EA-EJ adapters being available now....some of these folks are running WRX power (or NA EJ power) through dual range trannies or different combinations. I will say though....that most serious offroaders will simply weld up an open diff to go wheeling, then remove an axle for the road transit to/from a site.

Quote:
If you want to try, by all means go for it. But I wouldn't get your hopes up too high.

Phil
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I agree....what's the worst that can happen!
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Old 10-22-2009, 09:25 PM   #9
coldturbo
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http://wac.addr.com/auto/obs/lsd/lsd.html
This helped me to understand how it would work in an older Impreza chassis.
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