C6 Not Shifting Properly

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Sep 20, 2007 | 09:40 PM

Cool6.9DieselGuy

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C6 Not Shifting Properly

Hey C6 experts,

86 F350, I floored the throttle pedal on the truck getting on a highway at one point today and since then the truck is shifting into the next gear at much higher mph/rpm even when my foot is hardly on the pedal, I think I explained that good enough, anyways, I hardly know how these things operate, is there some kind of cable or linkage that needs to be greased up or replaced? or is this possibly a tc issue?(doubt it) where can I locate the problem. Thank you for anyone's time to reply.

Sep 20, 2007 | 10:51 PM

David85

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From: Campbell River, B.C.

There are two external imputs that the C6 uses to control stift timing, the vacuum modulator, and the kickdown rod.

The vacuum modulator is the dynamic contol that is used for normal driving, and the kickdown rod is used to force a downshift when ever the vehicle is floored. At least, thats how its supposed to work.

Both of these can be checked at the injector pump, the vacuum sensor (thats not what its called, but I can't remember the actual name) is on oppisite of the throttle cable, and has two vacuum hoses connected to it.

The kickdown rod is connected to the throttle lever through a spring loaded lever, its located toward the back of the IP on the pasenger side. It should move freely without binding, if it got stuck at the WOT position, this could be your problem.

Have your powerbrakes been affected at all?

Sep 21, 2007 | 01:27 PM

Cool6.9DieselGuy

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Quote:

Originally Posted by David85

Have your powerbrakes been affected at all?

YES! Acctually when I started reading about that vaccuum thing I was going to ask you if that had to do anything with the brakes... I was thinking maybe they needed some bleeding, lol, I guess not, so what is my issue, that vaccuum thing? Where do I go from here? Thank you so much for your time David.
from Andrew

Sep 21, 2007 | 04:16 PM

DNewton

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From: Hesperia, So Cal

if your power brakes are not working properly, and the tranny is not shifting correctly, i would venture to say that your vacuum pump has gone out and needs to be replaced...

http://www.napaautoparts.com/masterp...on=Vacuum+Pump

thats a link to the pump, may not be the cheapest store to get it from,but it gives you an idea...

Sep 21, 2007 | 07:51 PM

David85

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From: Campbell River, B.C.

The vacuum pump could be gone, the drive beld could be gone, or there could be a vacuum leak.

I had belts fly off on mine twice so far. What actually happened is alternator belt broke up while I was cruising at 75, the only warning was the cruise giving up, a quick tromp on the brakes revealed a complete vacuum loss. To this day, I still find pieces of belt under the hood....

Check for vacuum at the vacuum pump itself, it should grab your hand as well as a powerfull vacuum cleaner, if that checks out, work your way to the vacuum manifold in the firewall and try to track down the leak.

What might help is to take the belt off the pump and turn it by hand (engine off) and you might hear a hissing sound from the source of the leak, if a leak is your problem, that is.

Sep 21, 2007 | 08:44 PM

Cool6.9DieselGuy

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well I had some belt slippage/squeel and apparently one belt fell off and another one blew appart, I could have sworn the belts were still on when I was having the problem but maybe they were slipping too much to work that pump, I'm going to replace them and then see where i'm at, thanks for all the help guys