The 3N71A Transmission was slowly eating the low-reverse return spring to the point the car wouldn't reverse uphill when warm.

 

I found a 3N71B out of a 280Z and set about removing the old and installing the new(er). 

 

After dropping the old transmission, I took the time to thoroughly inspect the flex plate and found some radial cracks 180 degrees apart. Fortunately, the new transmission came with the flex plate.

 

A second surprise came when we removed the backing washer. There was a circular crack with a substantial gap just underneath the washer. There is perhaps two or three points of contact. I can't tell whether the crank had spun the portion on the backup washer, caught and re-welded itself into place, or if the crack just hadn't finished the full circle.

 

The car drove normally and this came as a complete surprise. Who knows what evil lurks in the hearts of our beast.

 

The only other problem in the installation is a failed diaphragm in the vacuum modulator that is getting replaced tomorrow.

 

Has anyone else experienced a similar failure?

 

Edited March 11, 201510 yr by djwarner

When I took the flywheel off the automatic L24 I bought I felt how light it was and got all excited, then I realized there was no friction plate on there.  I thought I had an expensive lightened flywheel.  ::

 

Wow, I clicked on your's.  You were about to be walking home.

Edited March 11, 201510 yr by siteunseen

glad you caught it - i shudder to think about how much damage those pieces could have inflicted if they flew apart in the upper rev range.