Play in drifeshaft?
 

New issue. When I step on the gas, there's a slight knock, and it feels like it's coming from the rear end.
Threw the car on the lift, and there's some play when turning the driveshaft and before the wheels engage.

After a brief search, I understand that I gotta check the U-joints, right?
Yet, could it be that the diff is going? (Itza 1.8 from '96). If so, it'd be a good time to chuck the RX7 internals in it, methinks.

Thanks, gents!

P.S. Another question. I've perused (very carefully) the RX7 swap instructions, but I still can't make heads or tails. How does one tell whether the diff is from a non-turbo car? And, I'm looking for an '86-'88, right?
Also, swap the RX7 pumpkin in place of 1.8?

Again, thanks!

i would just buy a used driveshaft, i bought one from ebay for $60 shipped.