Electronic 4WD hows it work

Mick G · Post by **Mick G** » Wed Apr 24, 2013 7:18 pm

Could anyone please explaine how the Clutch pack in the rear of the Auto's work.
I would like to replace a Viscous center diff (for Motorsport)

Gannon · Post by **Gannon** » Wed Apr 24, 2013 8:13 pm

What gearbox have you got? 4 speed from an EJ powered Subaru or 3 speed from a MY touring wagon?

Most Subaru autos dont have a centre diff, but have constant drive to the front wheels and a electrical/hydraulic clutch (known as MPT) to vary torque to the rear wheels, controlled by the TCU (or 4WD swich on 3 speed models) No auto Subaru's came with a viscous centre diff, only the manuals did but some turbo and H6 auto models came with a rear biased centre diff known as VTD.

What exactly do you need to know?

Mick G · Post by **Mick G** » Thu Apr 25, 2013 5:14 am

The clutch pack came out of there MY turbo auto
The place If like to use it is in there back If the 96 WRX 5 speed manual

Gannon · Post by **Gannon** » Thu Apr 25, 2013 9:54 am

Mick G wrote:The clutch pack came out of there MY turbo auto
The place If like to use it is in there back If the 96 WRX 5 speed manual

I dont quite understand what you wrote, but I'll take a guess

You want to put the MPT or VTD from an auto gearbox in the manual gearbox in your 96 WRX manual.

It wont fit. The 2 gearboxes are completely different.

What model and year auto gearbox are you talking about, just out of curiousity?

What you want is a DCCD centre diff, which is the same principle as the VTD, but designed for the manual gearbox.

The DCCD is a planetary differential with a rear bias, either 35/65 for early models or 41/59 (front/rear) for later ones. Being a 96, the 35/65 will apply to you
It has an electro/mechanical clutch to provide LSD limiting which means that you can, via an electronic controller, vary the torque split from open 35/65 split (full differential action/no LSD action) all the way to 50/50 locked (no differential action/full LSD action).

steptoe · Post by **steptoe** » Thu Apr 25, 2013 10:13 am

MY EA81 turbo auto ? Be an import? Same as the 85,86 GLTA 4WD 3 speed auto EA82 L Series sedans - JATCO with 3.7 diff rear, 3.45 front diff

Mick G · Post by **Mick G** » Thu Apr 25, 2013 10:17 am

After removing the auto one from there box 1986 rx auto, I see there problems
You are right Gannon there will not fit
I was just after an cheap fix My viscous wore out 12 months ago and I welded It up.
Works great in loose stuff,but my hydraulic hand brake fitted to rear discs now locks up the front wheels too,
I wanted to be able to have access to there hydraulic hand brake again.

Gannon · Post by **Gannon** » Thu Apr 25, 2013 10:42 am

I think he may be confused. I think we are talking all EJ stuff here

Mick, an easy way to control the MPT in your current gearbox is to disconnect the wire to the transfer solenoid, this supplies maximum pressure to the clutch plates in the MPT and makes your car practically full 4WD. This is at the mercy of the clutch plates and will wear them quicker.

If you wanted to be tricky, devise a simple variable duty cycle/pulse width modulator circuit and wire it into your transfer solenoid so you can control your 4WDness manually

Gannon · Post by **Gannon** » Thu Apr 25, 2013 12:15 pm

I may be confused,.. I thought we were still talking autos.

You can either get a new centre diff (or used) and replace it, or upgrade to DCCD, the latter will likely cost you more but with a biasable centre diff, you can have much more control of your power on understeer/oversteer