VT S1 wagon - auto doesn't stay in 4th gear

[ZKFVS]

Hi all,

I've recently bought this VT V6 wagon with 267k's on it, all is good on it except for one thing. When I'm going along the highway it'll be happily sitting in 4th as it's supposed to then all of a sudden it'll downshift to third and stay there. If I stop the car and turn it off and on it is ok again for awhile then does it again, weird thing is, if I let off the accelerator completely, say to go down a hill it seems to shift back into 4th until I give it gas again, I figure this becaue if I manually shift it down to third I can feel it change down and the revs pick back up as it's engine braking. The trans has just been given a full flush and it had been flushed 40,000k's before then too. All the other gears are fine and shifts are smooth - when 4th is working it is good just sometimes does this. Kick down works fine and so does a normal downshift to 3rd on steeper hills. Really hoping this is something reasonably simple and not something major. Thanks

[Feraljay]

Hi. I have the same prob with my vt wagon to. have taken it to a number of auto places 1 said it needs a service (done that) 1 said its the gearbox (dont think so) The funny thing is I find that when its been raining and been driving in it, It dont do it. so i'm thinking it's an elec fault, like the elec plugs on the box are dirty and causing this. try taking the pugs out spraying with WD or somthing like it. I have yet to do this as i cant get under to do it so its only a thought You can only try it...................