I have a RX7 1981 FB SA22C with a 12A engine. Does anyone have any ideas as to what this could be? I have a vibration that seems to be concentrated on the gearstick but only around the 3500 rpm area. Below 3500 or above and it disappears. I am not sure what this could be and would welcome some advice as to what it could be.

 

In gear or out of gear?

Clutch in or out?

Rolling or sitting still?

We need more info to help you out. It could be a few different issues but without more info we would be guessing.

 

In gear with clutch engaged and on the move.

 

More than likely the driveshaft u-joints. But check the pinon flange bolts and tranny mount too. Long term vibration can loosen/damage them.

 

I had a similar problem and I spent a month trying to solve it.
It turned out to be the front u-joint. I pulled the drive shaft and attempted
to replace the u-joints but could not get the front one out. I took the shaft
to a machine shop where they used a 55 ton press to remove it. They then
installed the new one. I installed the drive shaft and the vibration is gone.
My car is a '79. I used Neapco u-joints that I purchased at Advance Auto for
$11.99 each. The part number is 1-1606.

 

So only happens when your car is moving and in gear? Does it happen when youre in neutral and moving or neutral and stopped? If its only the first.. youre probably lucky that its driveline. Otherwise it could be incorrect year flywheel/clutch used that probably isn't put in correctly or if your engine has been rebuilt perhaps a wrong part in the rotating assembly was used that caused your engine to be out of balance. Just throwing out some scenarios but hopefully you have an easy fix and can enjoy your car running smoothly in no time. Good luck

 

Probably Ujoints or tranny mount. The motor wasn't recently rebuilt was it? Having the wrong flywheel for the motor could cause a vibe or two...



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I would also say u-joint of trans mount.

 

I had a similar vibration. I checked my driveshaft, It looked good. Changed my trans mount even though it looked OK. The trans mount fixed it.