wont stay in overdrive

[88ls1blazer]

i recently purchased an 87 turbo t, and am having a little bit of trouble getting the car to go/stay in overdrive no matter what position the tv cable is in, when i put the tv cable within one click of the factory setting, or at the factory setting it can go into overdrive, but if i back off of the throttle just enough it will almost freewheel and go back into 3rd, at least i am assuming it is 3rd because when i manually downshift there is no rpm change, but, as soon as i put my foot back into it, it upshifts again, i have NOT pulled the pan to check the filter, and im sure it could have some bearing on this, but the trans fluid does look to be in good shape, and is full, its really starting to tick me off being i sometimes have to drive it for 30 miles at a time, and do not want the trans to go out all together, some background on the car, it has a stock torque converter, and a stage right trans brake, other than that, it is a stock trans to my knowledge, and info is appreciated, Thank You

 

[88ls1blazer]

anyone have any ideas?

 

[Dafduc]

Maybe you wanna wait til it's running better before you drive it 30 miles at a pop...

Might save some money on insurance?



Dafduc

 

[88ls1blazer]

Any other ideas? please

 

[chris718]

put a pressure gage on the fourth clutch tap to verify if oil is present in the circuit or if the clutch is not applying.are all the shifts late?

 

[88ls1blazer]

i did find a way to make it stay in overdrive by adjusting the tv cable, but then the shifts are all late, the car did have a bad turbo on it, and i replaced it, which helped a little, but not totally

 

[chris718]

THAT DOESNT MAKE SENSE SO I WOULD ASSUME THAT THERE IS A HYDRAULIC PROBLEM IN THE VALVE BODY.

 

[88ls1blazer]

how can i determine if it is a valvebody problem, any signs to look for when i take it out? other than something like a missplaced checkball, or dirt?