Hard shift change on drive only
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Mountain Pass
Joined: Nov 2019
Posts: 139
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From: California
Hard shift change on drive only
I have a 1978 ford f100 302 c6 auto every time I go in drive I have a hard shift into drive only some times are harder than others what you guys think it is?
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Mountain Pass
Joined: Nov 2019
Posts: 139
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From: California
I might have explained this wrong. Almost every time I shift to drive I get a hard shift when driving truck shifts fine
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Mountain Pass
Joined: Nov 2019
Posts: 139
Likes: 12
From: California
manually. Trani shifts good only happens when I shift to drive
Hotshot
Joined: Feb 2004
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From: The Shenandoah Valley
I know that my '77 will seemingly shift harder from 2 to 3 if I had just manually held it in 2 like with a load on a grade, then shifted to 3 at the top as I'm letting up on the throttle. I'm at the point then that I'm like coasting, but the governor is ready for a shift. Maybe a poor explanation, but mine will do it and has as long as I can recall.
Just guessing ... but when the transmission controls the shift, it is some adjusted by vacuum. Higher vacuum often results in sooner shifts at lower rpms than does lower vacuum which one typically sees under load. There is a governor in there too, so rpms matter too. You manually shifting is delaying the shift to a higher rpm, but at higher vacuum too as it's not load determining shift, it's you determining the shift. A vacuum modulator modulates shifts.
Just guessing ... but when the transmission controls the shift, it is some adjusted by vacuum. Higher vacuum often results in sooner shifts at lower rpms than does lower vacuum which one typically sees under load. There is a governor in there too, so rpms matter too. You manually shifting is delaying the shift to a higher rpm, but at higher vacuum too as it's not load determining shift, it's you determining the shift. A vacuum modulator modulates shifts.
Fleet Mechanic
Joined: Feb 2022
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He’s trying to describe a “garage shift”, i.e. Park to drive or neutral to drive. You really don’t have many options available to you to improve the situation short of tearing it down and inspecting the entire transmission other than trying to get your idle speed down to decrease the torque input to the system. I know that before I started the resto on our truck that garage shifts typically sucked. It’s just part of the game for a lot of old transmissions, especially if you’re used to new technology that has a lot of “handles”, as we call them in the industry, to deliver a smooth garage shift.
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Hotshot
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Fleet Mechanic
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Yeah, that's part of it. The TCM is also capable of issuing a torque request to the engine via the air and/or spark path to allow the oncoming clutch to engage without a big disturbance. Clutch pressure and fill time can also be controlled based on various inputs like turbine speed, torque, etc. Strategies vary based on the manufacturer but those are the basics. C6s obviously don't have any of that capability.
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Mountain Pass
Joined: Nov 2019
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From: California
He’s trying to describe a “garage shift”, i.e. Park to drive or neutral to drive. You really don’t have many options available to you to improve the situation short of tearing it down and inspecting the entire transmission other than trying to get your idle speed down to decrease the torque input to the system. I know that before I started the resto on our truck that garage shifts typically sucked. It’s just part of the game for a lot of old transmissions, especially if you’re used to new technology that has a lot of “handles”, as we call them in the industry, to deliver a smooth garage shift.
Logistics Pro
Joined: Oct 2006
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From: East Central Ia
Let it warm up and idle drop to warm idle speed. That would be normal on high idle to hit gear hard. Older days were a little more difficult to before automatic chokes. Just a learning curve.
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