92 LS400 won't shift our of first gear!

[allen]

Hello,
I've got an intermittent problem with my 92 LS. Sometimes it won't shift out of first gear when I drive it no matter what I do. Sometimes it shifts just fine. Sometimes it shifts just fine until I come to a stop, etc. then won't shift past first again!
I've replaced the speed sensor twice but the problem is still there.

Any suggestions?

thanks
allen

 

[KDog]

Check fluid level.
Check that all wiring is in good condition and that all plugs are firmly seated.
Check resistance of the shift solenoids - they should be around 10-15Ω