97 V6 seems to have trouble shifting

Hey guys, kinda new to the forums, so here it goes.

My automatic 97 has about 145 to 150k miles on it (i dont know exactly how much, the odometer stopped one day and i laughed it off).

The problem im having is a the car is; im driving down the road and as i accelerate through first gear or 2, all is fine, and when i hit about 35 mph and the car wants to shift into the next gear, the car somewhat shakes (like when you run over those thin speed bumps that look like this across a road llllllll ) So im wondering whats going on, i figured it was some sort of acceleration issue, so i took the car into the shop, and now i have all new wiring and plugs, which solved a similar problem on another car but didnt remedy this situation.

So im wondering what could be going on with it, my top 5 guesses are pcv valve needs to be switched out, the trans needs to be checked out for cracks/leeks/maybe needs new fluid, perhaps something wrong with a linkage in the trans, or maybe the trans is loosing pressure via a crack or something. Also, i searched a little before i typed this up, and could the computer chip be doing something to cause this? and is this something that could be recognized via a tech linking the car into a PC? let me know what you think, and thanks for the oppurtunity to post. CharlieC
 
Sounds like a problem I had with my wife AND daughter's cars ('94 & "95). I solved my problem by adding a container (4 fl. oz.) of "Limited Slip Axle Lubricant Additive" to the transmision. Your have to get it from a Chevrolet Dealer in their parts department.

Try it -- Don't ask any questions about how or why it works cause I have not a clue as to the answer. :shrug: