Just wanted to leave a little info on what i did to fix my transmission shifting problem.the truck would wind out before shifting into 2nd then go into 3rd and go in and out of gears while driving on frwy. I went underneath and checked all electronic connectors on trans ,they were all ok.then found a rubber vacuum line on pass.side of trans that was loose.changed it out with a new one and presto!!! Transmission shifts perfectly ever after!! Hopefully this may help someone else out . Chuck.

 

Thanks for the good info Condor17,

 

Yes Sir,

That would sure do it. Without vacuum on those 400s, the governor pressure/modulator valve can't overcome the built in spring pressure of the modulator.

Don't see that much anymore since they've gotten away from using a modulator on the newer transmissions.

Good catch!

Allan