R31 Auto Trans Problem

[CPR1116]

Hi guys, I've got a 1990 series III R31 and I'm having a weird problem with the trans.

A couple of weeks ago the speedo started playing up, it would just sit on zero or swing from 0 - 100. At about the same time the trans stopped shifting gear. After a bit of trouble shooting the trans seems to be in second. It starts in second and then doesn't change gear. But I found if I stop the car and turn it off then start it again (sometimes I have to do this 4-5 times) the trans will then change gear correctly and seems to be running perfectly.

have changed the instrument cluster with no change and I have also changed the sender unit on the trans also with no change. I'm at a bit of a loss as to what else the issue could be. Has anyone else seen this problem / know how to fix it ???

I'm assuming that the 2 problems are related and if I fix one problem it may fix both.

Thanks

[Mr C211]

might be the gear the sender unit runs on inside the trans