can I remove the silencer air box under the hood like the first mod stang owners do?

and also i was told when i bought my car you can't shift while rolling from reverse to drive since the transmission doesnt have a slip-true or not?

 

Once the car has fully warmed up you can slip a bit, but I wouldn't suggest it.

 

Yes, you can take off the underbody cladding, take out the airbox & drop the intake silencer out the bottom of the car.



You shouldn't run reverse to drive on anything, ever. You can do it under 15mph (Lock-out), but it's an extremely wearing on the clutch packs of any transmission. Whoever told you that you couldn't do it because you don't have a limited slip differnetial is a complete dumb****. The differential has nothing to do with it.
Yes I've done it before & yes, you will leave a pair of black marks. Especially if you replace/adjust your parking brakes correctly & grab it when you start moving forwards.






An open differential will spin both tires whenever there is enough power transfer to spin them both. If you don't have enough power to spin them both, then you'll grab the driver's wheel by itself 90% of the time, or whatever the inside wheel is cutting a corner from a stop.

 

But you still shouldn't do it unless you can afford a new transaxle.

 

gain any hp or anything from removing them or just sound?

 

Mostly sound. You can swiss cheese the airbox with a holesaw if you want a faster way.