Where to start: No 3-4 shift or converter lockup

[tt460]

I searched the board here and couldn't see where anyone had posted a similar question here, so here goes:

My '87 GN has stopped shifting into overdrive as well as locking the TCC.

I'm thinking it's a solenoid... Anyone have any feedback or places where I should start looking?

 

[WE4]

Not saying it is...

But the two things common to your issue is the 4th gear pressure switch. BUT , Usually it will still eventually go to 4th. If the switch is leaking or broken , it could let pressure go not allowing either the switch to ground or bleeding so much that 4th will not move the shift valve. Pretty remote though.
BUT, that is the common dinominator between the two.
Place to start anyway.:smile:

Bruce
We4
Performance Transmission Services