so the car doesn't move when on the ground? Seems you have spent A LOT of money already. Subarus come with a hill aid/anti roll back type system that iirc holds the rear brakes until the vehicle starts to move forward. Could it possibly be this you're feeling? Its definitely a weird feeling compared to other manual transmission cars. The vehicle is AWD so its normal for all 4 wheels to be spinning, what exactly is the issue you're having? Not moving or just the clutch feeling?

 

The car does move but when throttle is applied it can't keep up and feels like the clutch is slipping.

 

The clutch felt like it was slipping so we replaced the transmission, flywheel, drive shaft u-joints, the clutch 3 times, transfer case, new slave cylinder, master cylinder.

Wow, that's a lot of parts changing.

With the MT, the persistent sense of the clutch slipping is often caused by an axle that either has a bad/broken CV joint (even though it's not hanging down), or is slightly out of the side of the differential.

When that happens, the ability of the engine to propel the car depends solely on the AWD viscous coupler inside the MT center differential. The coupler is not likely to provide the full torque capacity that a regular MT clutch has, and can "slip". In some cases, if the viscous coupler has failed totally (e.g., if the seals on the coupler have allowed the viscous fluid to leak out) and no longer works, it could leave a MT unable to move.

Raise the car and check each axle to see if the shafts on either side of each joint can be turned independently of the other (they shouldn't). Also, check that the inner end of the axles are fully inserted into the differential, locked in place, and unable to be pulled out except with force, e.g., a lever. If they have a baffle plate on the inner end (originals do), the baffle should appear to be unusually close to the differential case. If the axle moves out only a quarter inch or so, it disconnects from the side gear inside the differential and propulsion there is lost.

There's a fair number of threads and posts involving ATs and MTs with bad axles and axles or have pulled out. Given what has already been done, I think this might be something to verify before any other parts are replaced.

 

Wow, that's a lot of parts changing.

With the MT, the persistent sense of the clutch slipping is often caused by an axle that either has a bad/broken CV joint (even though it's not hanging down), or is slightly out of the side of the differential.

When that happens, the ability of the engine to propel the car depends solely on the AWD viscous coupler inside the MT center differential. The coupler is not likely to provide the full torque capacity that a regular MT clutch has, and can "slip". In some cases, if the viscous coupler has failed totally (e.g., if the seals on the coupler have allowed the viscous fluid to leak out) and no longer works, it could leave a MT unable to move.

Raise the car and check each axle to see if the shafts on either side of each joint can be turned independently of the other (they shouldn't). Also, check that the inner end of the axles are fully inserted into the differential, locked in place, and unable to be pulled out except with force, e.g., a lever. If they have a baffle plate on the inner end (originals do), the baffle should appear to be unusually close to the differential case. If the axle moves out only a quarter inch or so, it disconnects from the side gear inside the differential and propulsion there is lost.

There's a fair number of threads and posts involving ATs and MTs with bad axles and axles or have pulled out. Given what has already been done, I think this might be something to verify before any other parts are replaced.

Thanks we have tested that already and have looked at previous threads. Its weird because sometimes it happens and other times it hooks up when I'm driving. Is there a way to test the differential?

 

Can you post a video? I'm having trouble understanding the problem from your description.

 

Are yo0u sure that the clutch is being fully engaged? In other words, does the throwout bearing actually go all the way back and stop pressing on the pressure plate fingers? Unfortunately, I have no idea how to check for that on these cars. From your description, this would be the first thing I would suspect.

What can happen is that something is keeping the pressure plate from fully pressing on the disk, which will allow it to transfer only a portion of the engine torque, so the car might move when the clutch pedal is released, but the engine will rev up when you hit the gas.