C4 Tranny: I6 or V8 or Don't it Matter?

My suggestion is to take the tranny to a rebuilder familiar with the C4 and have him take a look. If the tranny internals are for an I6, he can modify them for a V8, if necessary. Other than the bell housing and torque converter, the C4 tranny externals are the same for both motors.
Best,
Al

The V8 C4 requires more clutches, which a trans guy can do. There are a few things that can differ for the Mustang too, primarily pay attention to the gear selector shaft on the driver side. It should be a flat, straight piece with a semi-circular end. If it's a "Z" shaped connector, it's for a column-shift car and that won't fit the Mustang gear shift connecting rod unless you do some mods to the rod itself. If it's not right, a trans guy can swap that out for you too. Also need to be sure it takes the proper type neutral safety switch.

In short, the internals are roughly the same, save for extra clutches for the V8, but the connections differ based on the car it came from. Good luck!

Thanks guys for the help, Any idea about the input shaft & output shaft not turning? I put a small pipe wrench on the ends and I could not get it to turn on either end. I am afraid I bought a boat anchor.

I wouldn't trust the pipe wrench, maybe try your driveshaft yoke and see if it spins? Either way, though, if you don't know where this thing came from or it's condition, I'd take it to a tranny guy. If it's not worth rebuilding he prob wouldn't charge you, maybe can trade you for one that works... or, get it nicely rebuilt for a few hundred bucks. I wouldn't trust an old C4 that's been sitting around.