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  #1  
Old 07-03-2008, 01:35 PM
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4WD Lock Mod

I've been looking through the forums and I see rumours of this but no real information.

Is there a mod that locks the car in 4WD (i.e. 50/50) mode? What would it take to do this? What are the pros and cons?

Just curious.
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  #2  
Old 07-03-2008, 02:30 PM
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Re: 4WD Lock Mod

Cliff Notes:

1. Yes you can do it... Put a single pole single throw switch on the Sol. C signal line. When it is switched to "on" it will be in normal operation...> Switch to "off" it will be in a 50/50 lock

2. Downsides, you will have significant torque bind and risk damaging the transfer components... They are already weak enough

Tom
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  #3  
Old 07-03-2008, 02:38 PM
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Re: 4WD Lock Mod

Quote:
Originally Posted by TomsSVX View Post
Cliff Notes:

1. Yes you can do it... Put a single pole single throw switch on the Sol. C signal line. When it is switched to "on" it will be in normal operation...> Switch to "off" it will be in a 50/50 lock

2. Downsides, you will have significant torque bind and risk damaging the transfer components... They are already weak enough

Tom
What He^ said!

I did it years ago and installed a full line pressure switch at the same time.
They make the car run like crap!
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  #4  
Old 07-03-2008, 03:34 PM
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Re: 4WD Lock Mod

Would it be worth it to put a switch in for better straight line acceleration, or does the transmission do this already? If it helps, you could only throw the switch to the "off" position when you're drag racing, unless it would be redundant (or in the snow to do donuts!).
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  #5  
Old 07-03-2008, 05:52 PM
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Re: 4WD Lock Mod

im actually really interested in this mod too. i tried finding stuff about it before also, but nothing on how to do it. if someone wrote a how to im sure id do it though. i just think it would be great just in case something messed up and the car wouldnt go in 4wd on its own (my car did that before). it would be kind of like an emergency thing, only use it when absolutely necessary. also i would be fun in the snow!!!!!

i know you couldnt drive it like that all the time, just if you absolutely needed it. i guess you COULD drive it like that, have fun ruining your tranny! lol
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  #6  
Old 07-03-2008, 08:47 PM
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Re: 4WD Lock Mod

I'm assuming this for the earlier non VTD transmissions? my 94jdm tranny has the duty c solenoid disconnected thus giving an open centre diff, powering the solenoid locks up the diff causing binding. Are we the lucky ones here in Oz i think all the svx's here were vtd? this is not the case in the US?
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  #7  
Old 07-03-2008, 11:22 PM
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Re: 4WD Lock Mod

Quote:
Originally Posted by legacyau View Post
I'm assuming this for the earlier non VTD transmissions? my 94jdm tranny has the duty c solenoid disconnected thus giving an open centre diff, powering the solenoid locks up the diff causing binding. Are we the lucky ones here in Oz i think all the svx's here were vtd? this is not the case in the US?
I'm pretty sure that the USDMs were not VTD on any year/model. Someone please correct me if I'm wrong (we buy more cars, but Europe/Japan seem to get all the fun stuff ).
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  #8  
Old 07-04-2008, 07:27 AM
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Re: 4WD Lock Mod

Heres a question for you guys then do your svx'i have the torque split favouring the rear (i think it is 65% rear) mine is still tail happy in the wet with an open centre
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  #9  
Old 07-04-2008, 11:03 AM
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Re: 4WD Lock Mod

Quote:
Originally Posted by legacyau View Post
Heres a question for you guys then do your svx'i have the torque split favouring the rear (i think it is 65% rear) mine is still tail happy in the wet with an open centre
No, the US model does not favor the rear... It is a constant variable clutch pack that it directly driven to the front wheels and clutch driven to the rear. IN most normal operation we see 90/10 and can see as low to 55/45

Tom
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  #10  
Old 07-05-2008, 12:07 AM
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Re: 4WD Lock Mod

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Originally Posted by TomsSVX View Post
No, the US model does not favor the rear... It is a constant variable clutch pack that it directly driven to the front wheels and clutch driven to the rear. IN most normal operation we see 90/10 and can see as low to 55/45

Tom
you poor fellas i love mine in the wet, i wonder who in subaru america made that decision ?
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  #11  
Old 07-05-2008, 04:57 AM
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Re: 4WD Lock Mod

Nobody knows.

There has been speculation here that this decision related to the need for some US states to dyno test the cars for emissions testing, and enabling the 2WD mode by removing the fuse bit in the cheaper transmission facilitated this.

Another possible scenario is cost; the US was a volume market for Subaru, but the prices charged for the SVX in markets that got the Japanese VTD box is actually double or more than what US buyers would be prepared to pay. So the logic is Fuji saved unit costs by using the cheaper rear assist transmission in low profit high volume markets. This argument carries weight because these "high cost" markets for the SVX had enough of a profit margin built in to cover the cost of what Americans would think of as "fully loaded" specification. These markets got everything included in the price except motorised 4WS and closing mirrors.

However, Germany, which is also a high spec fully loaded market, they also got the US type rear assist transmission, so maybe the dyno / emissions testing first scenario is what dictated the selection.

We may never know.

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  #12  
Old 07-05-2008, 05:30 AM
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Re: 4WD Lock Mod

Quote:
Originally Posted by Zandar View Post
I've been looking through the forums and I see rumours of this but no real information.

Is there a mod that locks the car in 4WD (i.e. 50/50) mode? What would it take to do this? What are the pros and cons?

Just curious.
What Tom said. I agree with his pros and cons. Further, I suspect you could actually do this [lock the centre differential] and drive on very loose gravel, or soft muck or in snow/sheet ice. There would not be high grip, so lower torque loads applied to the centre diff. It could be useful for "rocking" the car out of a stuck position.

On our VTD cars putting in the fuse locks this diff and the warning light comes on on the left upper dash position. I'll give you verbatim what the RHD owner manual says about this:
Section 3.10

Centre Diff Lock Warning Light:
This warning light comes on when a fuse has been inserted in the DIFF LOCK socket in the engine compartment, which is done to put the vehicle into the locked central differential drive mode during maintenance and service. For everyday operation the fuse should be removed from the DIFF LOCK socket and therefore, this light will not normally be on.


And from Section 10.4:

NOTE:
When tests with a brake tester or chassis dynanometer, such as braking force tests or speedometer tests, it is necessary to put a spare fuse [10A/15A] in the DIFF LOCK socket located at the fuse box in the engine compartment.
Confirm that the DIFF LOCK warning light comes on.


This second note is accompanied by a diagram showing the car with front wheels on a dyno roller, and the rear wheels either on jack stands [to spin freely] or on what is described as a free roller.

This probably indicates that the design function in both cases is to facilitate this dyno testing.

In the case of the US gearbox fitting the fuse disengages the centre differential from driving the rears [electrically, by disengaging the rear drive solenoid].

In the case of the VTD type, the fuse locks the centre diff 50/50, but the testing is done with the rear wheels spinning freely.

Joe
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  #13  
Old 07-05-2008, 06:45 PM
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Re: 4WD Lock Mod

where is the fuse holder for the diff lock? Don't worry i did the search function ( i went out and looked ) :P

Last edited by legacyau; 07-05-2008 at 06:58 PM.
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  #14  
Old 07-05-2008, 07:21 PM
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Re: 4WD Lock Mod

It's under the bonnet, where the fuses and relays are.
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