What a great forum this is!

My 85 GS started to "make a funny noise" last week while I was out of town, according to my wife. She took it to her mechanic brother who replaced the pinion seal on the differential. 50 dollars later (needless to say) the whine is still there - and so is the leak by the way!

Thanks to this forum, I learned several things to check.

The bolts that hold the pinion flange might be loose.

There is no gasket between the pinion flange and the pumpkin.

The bearings might be the problem.

The u-joint is also a possibility, but the RX-7 drive shaft has non-replaceable u-joints - so I'll have to replace the whole drive shaft if that is the problem. There is a bit of a "clunk" sound when transitioning from acceleration to deceleration, so this just might be the cause of the whine.

I hope that tightening the flange bolts will stop the leak.

Any other suggestions?

 

50 bucks says it's the driveline. I JUST replaced mine yesterday because of the same thing. It was clunking when I'd take off and it would growl when I let off the gas.

Replaced the driveline- no more clunking or growling. Works great now!!! Got mine from a junkyard for 7 bucks.

 

Here is a follow-up on what I found.

The bolts holding the differential together were all loose at least one complete turn! I tightened them up and the leak stopped.

The 50 dollar seal replacement job that my wife bought from her brother's automotive shop apparently did not include replacing the differential fluid. I drained what was in there, and out came about 1/2 the amount needed to fill it again. The color of the used oil that came out was very dark - unlike the honey colored stuff I replaced it with.

There is no free play in the u-joint, but there is about 1/4 inch of free rotation inside the differential. As you rock the drive shaft left and right, you can hear a tink-tink inside the differential meaning that there is some free play in the gears (maybe bearings?). I'm not sure if that is normal or should be adjusted out.

The whine is greatly reduced now, but you can still hear it in 4th and 5th gear only. The loudness of the whine depends on whether you are accelerating (loud) or decelerating (quiet). The pitch of the whine does not change when shifting from 4th to 5th. This suggests that it is related to wheel RPM, not engine RPM.

 

This is really common actually...All of my 7s have been like that. I just torque them down .

~T.J.