Question for you guys. I have a 1970 Riviera BT coded T400 in my GS. If I manually downshift the transmission in to 1st gear, give the car full throttle, the transmission will upshift to 2nd gear on its own before I have moved the shifter to the 2nd gear position. So I can downshift with the shifter, I just can't control upshifts at WOT. Any thoughts on why this is? All the other Turbo 400's I've had, held a given gear at wide open throttle, until I moved the shifter.
Stock turbo 400 will shift to 2nd when governor reaches its shift point. The transgo shift kit includes mods to have full control of shift points. Im sure GM did this on stock turbo 400 to protect the tranni. I believe you can modify the stock valve body to stay in chosen gears. Others will chime in with more experience.
IF the electrical downshift wire is not connected OR your NOT getting FULL throttle at electrical downshift switch for the trans. so the throttle is NOT providing enough pedal travel for the electric downshift switch will short shift at WOT. Otherwise starting in 1965 TH400's were designed to shift at 5500 RPM's even if the lever was in number 1 position. This was designed to save engines & excessive engine warranty replacements even on Chevy's. Tom T.
Keep in mind, once you do the 1-2 shift valve modifications, if the shifter is in first you will drive over the crankshaft and it still won’t shift. Ifyou are going a 100mph and pull the shifter into first gear, it’s going into first!
Thanks for the replies. So I guess the transmission is doing what it's supposed to do. Looks like I might want to modify the governor to raise my shiftpoints.
