1972 THM400 Shift Points
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Instructor
Joined: Oct 2012
Posts: 222
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From: Johnston, Rhode Island
1972 THM400 Shift Points
I have a 1972 350 Corvette with a THM400 automatic transmission and 3.36 rear gears. Can anyone tell me at approximately what speed or rpms should the transmission shift between first to second gear and second to third while driving normally and maybe at what levels under WOT?
Racer
Joined: Jul 2018
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From: Sandusky, OH
Light peddle: 1-2 about 10-15 MPH. 2-3 about 20-25 MPH.
WOT: About 4200-4500 RPM. I had a ‘70 Vette small block with a 400 TH. It short shifted about 4200 every time with the shifter in Drive. The car was “ killer “ consistent at the drag strip. I won twice and had runner up four times in a six week period. I was waiting on parts for my regular D/SA Camaro. And no, it didn’t kick butt as well as my daily driver Vette.
Steve O.
WOT: About 4200-4500 RPM. I had a ‘70 Vette small block with a 400 TH. It short shifted about 4200 every time with the shifter in Drive. The car was “ killer “ consistent at the drag strip. I won twice and had runner up four times in a six week period. I was waiting on parts for my regular D/SA Camaro. And no, it didn’t kick butt as well as my daily driver Vette.
Steve O.
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Instructor
Joined: Oct 2012
Posts: 222
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From: Johnston, Rhode Island
My car seems to shift from second to third around 40 mph when cruising. I never thought anything about this before as they are old cars with three speed automatic transmissions. The car drives fine, but I am wondering if this is normal.
Le Mans Master
Joined: May 2007
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From: North tonawanda NY
This is controlled at least in part by the vacuum modular I believe and its not a pricey part from what I remember I replaced mine a couple years back. They make adjustable ones as well which I believe I bought. very easy to change, old one unthreads and new one threads on then connect hose.
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From: Indiana Cornfield
