Help me diagnose a high pitch whine (audio link to listen to)

[Davbret]

Hello and thank you in advance. My 68 2000 has a high pitch whine seemingly coming from the rear end. Only at higher speeds (end of 3rd, mostly 4th and 5th due to speed), only on throttle. Immediately goes away off throttle. Going to be taking to the mechanic next week, but having a clue what it could be would be fantastic. Please take a listen, included is audio from the rear and from the engine bay. Thanks!

[Gregs672000]

Have you checked it for oil?

[JT68]

That is pretty much classic worn-out differential behavior- described perfectly.

[redroadster]

Mostly I hear the exhaust
A bit of wine. Sure it rear not trans
A. Electric steathascope is used to determine point of noises if it set for long periods the ring may have rusted out of the oil

[greydog]

Sure sounds like the cuff is worn.
Dan

[greydog]

Damn auto correct.
Diff not cuff.
Dan

[Davbret]

That is pretty much classic worn-out differential behavior- described perfectly.

Like needs a rebuild kit, or the gears are worn and need replaced?

[david premo]

Sounds link a bad differential from your video clip. The on acceleration only noise or on deceleration only is classic of a bad differential. What’s happening is the ring and pinion are no longer meshing properly. If it were a wheel bearing problem the noise would be constant. When a ring and pinion are not properly aligned it will ride high or low on either the ring gear or the pinion which will create the noise.

[greydog]

Chances are it's a total rebuild of center section. Ring and pinon gears plus assorted bearings.
You will have the axles out so makes sense to replace axle bearings and seals too.
You may get off cheaper by buying a known good diff from someone doing a ka or sr swap.
Dan

[JT68]

These guys (last two posts) are spot on. A good used diff is the least inexpensive route. (Either 3.89 1600 or 3.7 2L) j

[Gregs672000]

You have a couple choices... rebuild and "while you're in there" doing the wheel bearings and collars (will require a shop to redo the collars); replace with a good used complete set up (options there are staying with the 3.7 or switching to the 1600s 3.9 for better off the line response with a small change to your speedo readings, likely swapping over your brakes etc. Can likely be sourced from someone on the list, but one has to consider shipping vs local); see if you can find anyone doing the RX7 3.9, disc brake limited slip conversion like I did many years ago, but I haven't heard from the guy who did mine (John in Oregon?) in a long time and they became harder to find.
We're here to help!

[Davbret]

thanks for the replies everyone