There are many things that can cause a transmission to not shift into over drive. Brainstorming is not going to help, you need tests.

The transmission shift points are controlled by governor pressures. Governor pressure is a function of Line pressure that is modified by the valve body, the governor and the Vacuum modulator/TV cable. If a trans does not upshift right it has low governor pressure which can come from almost anything.

Test one would be to check the line pressure. (pump pressure) If at any point it the test drive the line pressure drops that indicates a major seal failure and you need a rebuild. This is a common issue when a car will not go into a single gear. If the seal in a given clutch pack is blown when system tried to fill that clutch pack the line pressure drops and it just will not go into that gear.

The problem with figuring out a 4th gear issue is that 4th gear requires the highest governor pressure and anything wrong with the governor system that will cause a drop off in pressure will act just like a blown clutch pack. So the real test to hook gages to the line pressure and the governor pressure and watch them. If both pressure drop when the car should be going into then you trans is toast but if all you see is the Governor pressure stop rising you could have an issue with the TV cable or the governor. Governors can be replaced without a complete rebuild.

I realize this is a lot to absorb, your best bet is to take to a good trans shop. Make sure you do some local research. If you are luckily you can find one that would figure out what is wrong and if it needs rebuilt they will let you pull it and reinstall. In a perfect world you find the really good trans tech and have him do it on the side.

 

I will check it sometime soon I work second shift and seems like I have no time for anything. And yes it currently will not shift out first now, while before it would not go into fourth. so something is definetly wrong with the cable or the transmission. Im hoping its not the latter of the two.

 

Pull the dip stick and look at it under magnification, if you see metal flakes in the fluid. If you do don't waste anymore time on it.


When I see a trans rapidly getting worse with new issues showing up quickly most of the time it is metal in the fluid and it is damaging seals and causing valves to not seal.

 

Checked the fluid and there where no signs of metal also adjusted the cable a bit and got it to shift again. still will not shift into 4th but at this point I'm pretty sure the problem is the cable so I'm going to adjust it and see if that works if not guess its time to check the pressure.

 

its important that you get the tv and shift cables set correctly. tv cable out of adjustment can ruin the trans fairly quickly. not right away but you don't want to be driving it for the long haul. not sure if the v6 trans is the same as the lt1 93 but if it is you have a trans that is a little different, has a round 5 pin plug for the lockup.