Engine and Trans Shake After Swap

[Soarer]

I just took my 1998 Legacy GT out for a ride after swapping in an EJ20t from a 2003 WRX. I used a version 2 5sp trans with 4.11 gearing and installed a new ACT street clutch and pressure plate with resurfaced oem flywheel. The motor is running great but, when I get the car started in 1st or reverse from a standstill, the motor shakes violently. I don't hav a hood on the car right now because my big TMIC won't clear the stock hood. So, I can see the motor shaking like crazy. I used the oem Wrx motor and trans mounts with 44k on them.

Anybody know why this thin is shaking and shuddering like this?

[jey]

At what RPM is it doing this?

[Soarer]

When I just do a normal start by revving the motor to 2000 to 2500 rpm an let the clutch out easy.

[LiCelsior]

possibly mounts?

[ouch1011]

I'd say clutch chatter. Possibly from oil contamination or an improperly machined flywheel. The more you slip the clutch, the more it will chatter.