1971 c3 gear selection
Thread Starter
Heel & Toe
Joined: Dec 2015
Posts: 15
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1971 c3 gear selection
Hi guys, I have a 1971 350 auto 3 speed. Wondering how the gear selection works as I haven't drove it yet as its still a ongoing project. I have park, reverse, neutral,1 ,2 ,3. Obviously I would put it in 1st but would I have to change up manually into 2nd and 3rd and back down? Seems strange there isn't a D for drive. Any help would be great, thanks
Melting Slicks
Joined: Mar 2005
Posts: 2,093
Likes: 297
From: Midlothian VA
Hi guys, I have a 1971 350 auto 3 speed. Wondering how the gear selection works as I haven't drove it yet as its still a ongoing project. I have park, reverse, neutral,1 ,2 ,3. Obviously I would put it in 1st but would I have to change up manually into 2nd and 3rd and back down? Seems strange there isn't a D for drive. Any help would be great, thanks
Drifting
Joined: Jun 2010
Posts: 1,312
Likes: 156
From: Richmond Texas
Hi guys, I have a 1971 350 auto 3 speed. Wondering how the gear selection works as I haven't drove it yet as its still a ongoing project. I have park, reverse, neutral,1 ,2 ,3. Obviously I would put it in 1st but would I have to change up manually into 2nd and 3rd and back down? Seems strange there isn't a D for drive. Any help would be great, thanks
3 is D.
Last edited by ZAKsPop; Jan 24, 2016 at 07:32 PM.
Drifting
Joined: Oct 2012
Posts: 1,524
Likes: 61
From: Medina Ohio
If it truly is 1 2 3, he has a reverse valve body, commonly modified for drag racing. If that's the case, you usually have to shift them manually through each gear and cannot go straight to "3" for drive like it would be if standard 3 2 1.
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
'71 automatic cars has the THM-400 turbo hydramatic transmission in them when new. If you have a THM-350 in the car, it has been changed out. The 400 was a MUCH stronger transmission than the 350.
Both operate om the same manner PRN321. You can put the shifter into any forward range and the car will start out in first gear, then upshift to the range specified on the shift indicator. You can downshift at any time, but there are 'inhibitors' which prevent the car from going into a lower range IF doing so would cause the trans to overspeed.
Both operate om the same manner PRN321. You can put the shifter into any forward range and the car will start out in first gear, then upshift to the range specified on the shift indicator. You can downshift at any time, but there are 'inhibitors' which prevent the car from going into a lower range IF doing so would cause the trans to overspeed.
Last edited by 7T1vette; Jan 25, 2016 at 01:32 PM.
Racer
Joined: Apr 2015
Posts: 296
Likes: 30
From: Westchester NY
Sorry to threadjack.... But does this mean you can shift into any gear like you would with a slapstick without fear of hurting the engine and transmission? AKA if I want to do a hard pull onto the highway from low speed I can shift into 1 and accelerate until 4.5k rpms before going back into 3?
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
All automatic transmissions have downshift inhibitors to prevent the transmission from overspeeding when shifting into a LOWER gear. If rotating parts are spun too fast, they will simply explode and create a wall of shrapnel.
I don't know if ALL turbo-hydramatic transmissions would automatically shift out of a lower gear on their own[when left in that range] or not. I only know that the one in my (then new) 1968 Chevelle 396 SS would shift on its own out of low gear. I could keep the hammer down and, with a strudy-enough jock-strap, it would eventually shift to 2nd. And shift it did!! Hard and fast...fishtailing a bit till it settled down. That was fun.
My later 'fast' cars had stick shifts in them; then I did the 'family' thing and got out of the rapid car market. When I got back into C3's and had another THM, I didn't really feel the need to "test" that feature out. Maybe they all do it. I don't know.
NORMALLY, one would put the shifter into 1st range and shift to 2nd at the proper rpm. Or, if the governor was set up well, just put it in Drive and hold the pedal down; the governor will shift it automatically when the set rpm is reached (usually a lot lower than one would desire, as set from the factory).
I don't know if ALL turbo-hydramatic transmissions would automatically shift out of a lower gear on their own[when left in that range] or not. I only know that the one in my (then new) 1968 Chevelle 396 SS would shift on its own out of low gear. I could keep the hammer down and, with a strudy-enough jock-strap, it would eventually shift to 2nd. And shift it did!! Hard and fast...fishtailing a bit till it settled down. That was fun.
My later 'fast' cars had stick shifts in them; then I did the 'family' thing and got out of the rapid car market. When I got back into C3's and had another THM, I didn't really feel the need to "test" that feature out. Maybe they all do it. I don't know.
NORMALLY, one would put the shifter into 1st range and shift to 2nd at the proper rpm. Or, if the governor was set up well, just put it in Drive and hold the pedal down; the governor will shift it automatically when the set rpm is reached (usually a lot lower than one would desire, as set from the factory).
Last edited by 7T1vette; Jan 25, 2016 at 07:44 PM.