i have an 88 formy with a 5 speed. when i put it into 1st gear and drive the car makes this like jumpy pully feeling i cant explain it but it feels like the rear axle is rocking back and forth its more or less a jerking motion whats going on with this?

also my friend has a 94 formula hes selling his rear its a posi disc would this fit my bird? if it can be used. what all will i need from the parts store/summit to get this bad boy to go in

 

I understand It should bolt right in. It will stick out an extra 2" each side but thats no biggie. I believe you just need to get the brake lines firgured out if I remember correctly. I've wanted to do the same thing with my TA.

As to whether or not it will fix your problem......does it do that with all gears or just 1st? And how's the clutch? old, new, who knows?