1971 Chevrolet Chevelle • V8 2WD Automatic •

Why does my trans not shift into 3rd gear until im going 55 or60 miles per hour
April 22, 2011.

Your transmission uses a vacuum modulator at the right rear right above the pan. Start by checking the vacuum hose and metal pipe going to it for leaks. If there is transmission fluid in that hose, replace the vacuum modulator.

Apr 22, 2011.
This shold be a 250 or350 transin thecar there area couple of things. First I wold check is the throttle pressure cable to see if it's adjusted properly, then check for a broken hose going to themodulator and on the engine. You may have a rusted pipe going down to the modulator as well. If it's any more than that then take it to a trans shop because the trans mayhave been modified, causing it to do this.

Jun 5, 2011.