Understanding the Gen 4 Dual Mass conversion

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Understanding the Gen 4 Dual Mass conversion

Postby art_fanatic » Mon Nov 27, 2017 5:10 pm

Subaru clutches are fairly new to me so am hoping to learn more about them :D
The thrust bearing has gone (chirping) so my Liberty's clutch is getting replaced. Mechanic was unsure if I have a Dual Mass or Single mass and has quoted for both situations. He explained that a conversion is a common practice for these models and looking through the forums and online, it appears there is virtually no difference in performance.
Has anyone who has had the conversion got any thoughts they'd like to share? If I have a dual mass I will be going ahead with the conversion as I want to keep the car for a while and past the next clutch change.

Below are the quotes, they sound fairly reasonable to me. He said it may be +$100 for machining, fluids etc

Option 1 - Dual mass to single mass conversion
- 5hrs = $550
- ACS Single mass clutch conversion kit $817
- Total: $1367

Option 2 - Single mass Flat*
- 5hrs = $550
- ACS clutch flat kit $363
- Total: $913

Option 3 - Single mass w step*
- 5hrs = $550
- ACS clutch step kit $586
- Total: $1136


*apparently there are two types of single mass flywheels, one thats completely flat and one that has a step.

My exact model is the standard 2.5L 2004 Liberty Wagon 5sp
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Re: Understanding the Gen 4 Dual Mass conversion

Postby Turbo Lag » Wed Nov 29, 2017 2:15 pm

I've had the DMF > SMF conversion done a few years ago. Yes it's quite common and many of the cars I went to look at at the time had it done. I went with an OEM Exedy SMF conversion kit as it was very easily available and wasn't too pricey. My DMF was on the way out and eventually exploded and stuck itself nicely on to the block which made the cost ridiculous - altogether came to around 2k. That said there's no way I would go back to a DMF. The SMF feels somewhat more responsive and should also be lighter I believe? If you're keeping the car for any amount of time I'd just get it done. Not sure of the different types of flywheel.
'04 Subaru Liberty 2.5i Safety Pack 5MT OBP - Rebuilt EJ25 N/A - SMF Conversion - Shockworks Coilovers - 2012 WRX Wheels - Michelin PS4 235/45/17 - RDA Slotted/Dimpled Rotors - Intima SS/SR Pads & '08 Subaru Liberty 2.5i 4EAT
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Re: Understanding the Gen 4 Dual Mass conversion

Postby BillyCorgi » Wed Nov 29, 2017 3:47 pm

Okay,

So Junior No.1 Son had a MY2002 Outback where the thrust bearing shat itself as described. The Clutch required replacing.
We did a Dual-Mass to Single Mass conversion.
Most noticable difference was a slight change in NVH and bad response when driving over a speed hump. like exist in parking lots.
The Car would surge badly when traversing the hump.
He learned that the clutch pedal had to be stabbed in when going over the hump to prevent the car bucking and jerking.
Not saying that everyone would experience this, just that Junior did experience it.

You car is unlkely to have a dual mass, as these were phased out in Gen3 due to a bad noise (like running over a sqealing cat) coming from dual mass flywheel clutches.
BUT, you can never tell until you have openned up the clutch, cause one can never tell with Subaru.
(Example, does a 2.5 GT-B turbo with 6MT have a 230mm or 240mm friction plate? Well, it can have either, just depends?)

The most likey clutch is what is called a Flexible Flywheel, which you have referred to a "stepped".
These are an inner and outer section joined together by a "flexible" backplate.
Dual masses however with rigid connection.
Google it for pictures.
The flex plate "flexes" slighly under the force of the Clutch Cover clamping the friction plate and gives some of the NVH benifit of Dual Mass system without the embarasement of the squeeling feline sounds.

When we changed the clutch in Junior No.2's MY2009 Gen4 Wagon, we had Northern clutch and Brake in Melbourne (Exedy Direct) on notice and when we knew for certain what clutch it was, they arranged fior the correct clutch kit to be delivered out of Arndel Park warehouse to Yagoona in an hour.
By the way, his was a Flex Flywheel (the stepped one)
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Re: Understanding the Gen 4 Dual Mass conversion

Postby ICE_BM » Fri Dec 22, 2017 12:27 am

Further question on this topic:
Does anyone know with any confidence if the bolt patterns for pressure plates are all the same on these conversion kits? I have a solid flywheel on my 2006 EJ253, prev owner reckons he converted it from dual mass, but that might go against the comments above suggesting dual mass were phased out earlier?
So if I have a solid non stepped flywheel can I get any pressure plate of that type as a replacement?
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Re: Understanding the Gen 4 Dual Mass conversion

Postby BillyCorgi » Fri Dec 22, 2017 7:41 am

ICE_BM wrote:Further question on this topic:
So if I have a solid non stepped flywheel can I get any pressure plate of that type as a replacement?


The answer is "depends".

(1) I know that you did not ask this, but you should not mix "flat flywheel" and "stepped flywheel" pressure plates.
(2) some single mass conversion kits also required (came with) a repalcement throw-out arm to set the new installation up at the
correct heights.
(3) When we did no.1 Son's MY2002 clutch, the SMF kit came with a "note inside the box" about what parts to re-order "next-time". His kit was FJK-7374SMF

So you may not really know what you need until the clutch is removed?
Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
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Re: Understanding the Gen 4 Dual Mass conversion

Postby ICE_BM » Fri Dec 22, 2017 11:08 am

BillyCorgi wrote:So you may not really know what you need until the clutch is removed?


I have it out.

Exedy FJC524 on a flat solid flywheel

Any thoughts on going 'one step stronger' than this, or is the FJC524 (in good condition) a good choice?
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Re: Understanding the Gen 4 Dual Mass conversion

Postby BillyCorgi » Fri Dec 22, 2017 12:33 pm

It may come down to your own needs?
From another thread you may recall that I have recently changed my clutch for an Exedy HD unit.
It is a little heavier, but one gets used to that quickly.
The NVH for some reason improved and the launching off teh line also improved.
With good judgement of the clutch foot and duse of teh throttle the response off the line is better and more predictable and one can get away better.

What suits me may nt suit you; different person; diffeent car.

If you alread have the Single Mass Flywheel with 225mm diameter friction plate, then your choices are Standard or HD?

The HD unit is sure to piss off any of the fairer sex when they first drive your car.
Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
Get your Gear Shift Rejuvenation Kit viewtopic.php?f=68&t=31240
Get your Centre Differential Rebuild viewtopic.php?f=6&t=31089
Want a custom built Brake Cylinder Stopper? viewtopic.php?f=6&t=31321
Need to hire a Guard Rolling Machine? viewtopic.php?f=6&t=31899
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Re: Understanding the Gen 4 Dual Mass conversion

Postby ICE_BM » Fri Dec 22, 2017 3:31 pm

BillyCorgi wrote:
If you alread have the Single Mass Flywheel with 225mm diameter friction plate, then your choices are Standard or HD?



My hand is forced somewhat, being the last day before break and Perth not known for high stock levels. The plate is 225mm, but the exedy is out of stock at Perth warehouse (though the out of stock was apparently a surprise to them)

So I have a complete kit including new flywheel (clutchpro brand), only option available at this time. Hopefully it goes in OK
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Re: Understanding the Gen 4 Dual Mass conversion

Postby ICE_BM » Sat Jan 13, 2018 12:58 pm

For the record here is the Clutchpro lightened flywheel (as supplied), looks like more 'thought' has gone into this one than the Exedy that I took off.
The hole pattern (for the pressure plate) was very-very close between the two brands (I could have tapped the Clutchpro pressure plate onto the Exedy flywheel), but the fit between the Clutchpro pieces was perfect slip-on and I was always going to change everything once I had no choice but to get a full kit.
The clutchpro kit included new fork (in genuine Subaru packaging), aftermarket thrust bearing, new pilot bearing, grease, clips, and a plastic dummy shaft for alignment
Attachments
Clutchpro-flywheel.JPG
Clutchpro lightened flywheel 4GEN 5MT
Clutchpro-flywheel.JPG (123.43 KiB) Viewed 739 times
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