OT 1971 Ford C6 Trans

Aaron Ford · May 25, 2018

Hello. Does anyone know if a C6 trans will downshift from second to first by design? I get a good 3-2 but no 2-1. Thanks Aaron

merlynr · May 25, 2018

(quoted from post at 12:03:25 05/25/18) Hello. Does anyone know if a C6 trans will downshift from second to first by design? I get a good 3-2 but no 2-1. Thanks Aaron

If your in 2 it stays in 2. If your in D and going too fast it won't go to low.
Back in the day a lot of troubles were cured with a new diaphram. It's what the vacuum line hooks to at the tranny. Especially if you find fluid in the vac line.

Keith True · May 25, 2018

Do you mean downshift while pulling up a hill?,or,are you getting second gear starts after driving it?Are you saying it won't drop into first on it's own at a stop sign? I pushed a lot of snow with those transmissions,and sometimes on a hard push I thought it should drop into first but it wouldn't.I would have to pull the lever down by hand.The transmission guy here told me that I was asking too much out of a vacuum controlled valve,and that's what the lever was for.

Hobo,NC · May 25, 2018

Governor is stuck good luck getting it unstuck... If you stop put in reverse and back up then put it in drive and it takes off in first at least one time the governor stuck.

Keith True · May 25, 2018

Something just came to me about those transmissions.If the spring rusts off the kickdown rod coming up from the transmission the rod will float back and forth,and make for some weird shifting.And,the way it floats back and forth it will give you 5 different symptoms.Also,if the kickdown rod hasn't been engaged regularly it will stay pushed back when it does get kicked back.Just grab it and either yank or push on it,I disremember which,it should spring back on it's own to where it is supposed to be of the spring is good and it is free.

leroy in ne · May 25, 2018

vacuum modulator was mentioned below, a split or unhooked hose, rusted thru line ect. will cause low vacuum as well as a bad modulator diaphragm.

Hobo,NC · May 25, 2018

(quoted from post at 05:40:15 05/26/18) vacuum modulator was mentioned below, a split or unhooked hose, rusted thru line ect. will cause low vacuum as well as a bad modulator diaphragm.

It won't affect downshift but will the up-shift.
The kick down/throttle pressure affects it the same It won't affect downshift but will the up-shift...

YprDave · May 25, 2018

(quoted from post at 12:03:25 05/25/18) Hello. Does anyone know if a C6 trans will downshift from second to first by design? I get a good 3-2 but no 2-1. Thanks Aaron

If you're in Manual 2nd, it will NOT downshift into 1st (unless you downshift manually).
If it's in Drive, it should downshift automatically when you're going slow enough, and/or floorboarding the gas pedal...assuming the kickdown linkage is attached and is adjusted right.
The vacuum modulator delays an automatic upshift, and typically doesn't do much in the way of downshifting (could still be an issue though if it's sticking, leaking internally, or out of adjustment) It might even be adjustable(some are, some aren't). To see if it is, pull the vacuum line off it and look for an adjusting screw inside the nipple.
A sticking governor could also prevent an automatic downshift. More of a PITA to fix that as the driveshaft and tailshaft housing would have to be removed in order to get to it.

MarkB_MI · May 26, 2018

As everyone else said, if it won't kick down into first, something isn't right.

Interestingly, the earlier "Cruise-O-Matic" transmission featured a shift position between 1 and D that prevented the transmission from shifting into first. It was intended to be used to prevent wheel spin when starting on slippery surfaces.

OT 1971 Ford C6 Trans

Aaron Ford

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merlynr

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Keith True

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Hobo,NC

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Keith True

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leroy in ne

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Hobo,NC

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YprDave

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MarkB_MI

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