Hello, my 70 cutlass has a freshly rebuilt TH350 with only a couple hundred miles put on it since the rebuild. It was working great, shifted really nice and tight like a new tranny feels. All of sudden this past weekend I took it out and something is not right. It won't shift into 3rd unless it hits 3000 rpms and while cruising around 60-65 mph the car feels like it's hesitating or being held back. Almost like the tranny can't decide what it wants to do. If I shift it down to 2nd and then back to 3rd it shifts right away. I am wondering if this could be a vacuum issue? The fluid is at proper level and still looks brand new. Any thoughts are appreciated, I have no problem just bringing my car to the shop to have it checked but thought maybe I'd ask first and see if it was something I could check out myself.

 

Even though there were no replies to this one I figured I'd update it. I got a chance to look things over. Thankfully all that was wrong was the vacuum line to the tranny had come off at the modulator. Easy fix

 

Wow I can't believe we missed this one. This happened to me on my T400 recently and it turned out to be a dried out and cracked vacuum line to the modulator. What was happening to me was the shift points were progressively getting higher and higher due to the vacuum leak.