Diff play - How much is too much?
 

Hi All,

My FD has quite a bit of driveline slack (has a habit of jerking back and forth with power on-off, especially at low speeds) and I've been on a mission to eliminate as much of it as I can. I've just finished changing out the stock differential bushings (which were badly torn) for Powerflex Purple urethane. That made a positive difference, but it's definitely still there.

My suspicion is that it's either the motor mounts or the diff itself, and I'm starting with trying to diagnose the diff's health.

To try to gauge how bad the diff might be, I attempted a test I read on another diff-play thread.
Gearbox in neutral, ebrake on, twist the prop shaft back and forth and mark how much play there is. So in the pic below, I was able to twist it freely until it locked at the spots marked by the two dots-


https://cimg9.ibsrv.net/gimg/www.rx7...b741f1ab7d.jpg

So there you have it, looks like I can get maybe 14ish degrees of free play before the teeth engage. Is this a tired/worn diff? Or is my problem elsewhere?

Thanks in advance for the help!

I have not done that specific test, but in general I've not seen people running into problems with their diff getting loose or causing a lot of play.

Diff bushings are a great starting point, next see if your motor mounts are broken then look for cracks in the PPF. Had a buddy who had bad driveline slop for ages, turns out his PPF was cracked and it was all over the place.

Dale