C6 Tranny question
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C6 Tranny question
I've got a 72 F-250 360/2bbl with a C6 tranny in it. I bought it back around 1995 [the truck], and the first thing I noticed is it seems to shift into 3rd gear pretty early, not allowing the rpms to get up there a bit before it shifts. I couldn't tell you exactly when it shifts since it is at a lower speed than normal, you never feel it shift. Also, it wastes no time decelerating, meaning if you let off the gas at say 65, in no time at all you can be doing 50. Any ideas? Are the two things related to each other?
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No tach? Do you know your tire size, gear ratio and the mph it shifts 1-2 and 2-3? Early, low rev shifting would be normal at part throttle. WOT, it should rev out higher. Is there a difference in shift points at WOT vs. part throttle? Does it downshift when you accelerate and apply WOT?
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No tach? Do you know your tire size, gear ratio and the mph it shifts 1-2 and 2-3? Early, low rev shifting would be normal at part throttle. WOT, it should rev out higher. Is there a difference in shift points at WOT vs. part throttle? Does it downshift when you accelerate and apply WOT?
@WOT 1st->2nd - 20mph, 2nd->3rd ? never stayed on it to see.
Yes, it will downshift or pick up passing gear if you are going slow enough to need it. I tried another modulator on it a few years back, and I can't remember exactly what it did, but it wasn't an improvement so I put the old one back on and left it.
Fleet Owner
Joined: Jun 1999
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From: Creedmoor, North Carolina
Not to argue, but it sounds like the C6 is shifting about normal to me. If it has an adjusting mod down on the side with vac. hose attached (some don't) you can place a slender screwdriver in there and make 1/4 turn adjustments that will move shift points. It has been over 10 years since I did it, so some backup may be needed.
The C6 is not an overdrive tranny so it has different shift patterns from today's trannys if you are comparing.
John
The C6 is not an overdrive tranny so it has different shift patterns from today's trannys if you are comparing.
John
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Joined: Jan 2011
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From: Antelope Valley ,CA
agreed , sounds like stock shifting , if you want to alter it get a shift kit , pretty easy to install and makes a big difference . How many miles on the trans ? if a lot ,you might want to have it rebuilt too .
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From: Middle Tn.
Not to argue, but it sounds like the C6 is shifting about normal to me. If it has an adjusting mod down on the side with vac. hose attached (some don't) you can place a slender screwdriver in there and make 1/4 turn adjustments that will move shift points. It has been over 10 years since I did it, so some backup may be needed.
The C6 is not an overdrive tranny so it has different shift patterns from today's trannys if you are comparing.
John
The C6 is not an overdrive tranny so it has different shift patterns from today's trannys if you are comparing.
John
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Thank you guys for your replies. I'm going on the assumption that it's a stock tranny with no performance type mods having been made before I got it. Knowing a little of the history of the truck and it's original owner and second owner and all. Both previous owners have passed on now, so I can't ask them. As you've probably figured, it's not a major issue or anything, was just wondering about this. Most automatic trannys I've had were a little more distinguishable when the shift occurs.
I put dual exhaust on it a few years back hoping I' could hear it change that way, but no such luck. I guess when you're trying not to break that egg under your right foot, this is normal shifting. Thanks again guys for your help on this.
I put dual exhaust on it a few years back hoping I' could hear it change that way, but no such luck. I guess when you're trying not to break that egg under your right foot, this is normal shifting. Thanks again guys for your help on this.
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Fleet Owner
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From: Creedmoor, North Carolina
You can adjust the shift points if you like, but the C6 is a soft shifter by design. Big thing is they are bullet proof. Drive on, enjoy.
John
John
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I'm thinking I might put a tach on it though; maybe I can see the change there. But I can stop wondering about this. Thanks again for your input.
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