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diymirage

C6 transmission not engaging

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hey guys 

i had this transmission rebuild last year, so it should be good 

 

lately its been not always wanting to go in gear 

at first i thought it was just converter drainback but today it did something weird 

 

it went into gear, and i drove a few yards, then when i went to back it up, nothing happened 

at this point it wouldnt go forward either 

 

i got under there, and best i can tell the linkage is good 

 

any thoughts whats going on here?

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Yo diy,

Screenshot_20170314-104223.png

 

Screenshot_20170314-104248.png

Vacuum Modulator on passenger side of transmission; Check for vacuum at mod. Should be around 16 - 21 psi in idle.

Pull vac line off,if there is a flow of trans fluid, replace modulator.

Low fluid level

Shift linkage;Purl="http://web.archive.org/web/20101224143958/http://ylobronc.users.superford.org/documents/linkage3.gif"]http://web.archive.org/web/20101224143958/http://ylobronc.users.superford.org/documents/linkage3.gif[/url]"

Parts Break-Out Diagram in an 88 with nomenclature @  http://web.archive.org/web/20051229052026/http://ylobronc.users.superford.org/documents/linkage3.gif">http://web.archive.org/web/20051229052026/http://ylobronc.users.superford.org/documents/linkage3.gif

by Dustin S (Dustball, Mellow Yellow, Mr. Laser Boy

 Vacuum Modulator Replacement in an 89; "..The different color bands indicate the diameter of the rubber diaphragm inside the modulator. The two COMMON colors from auto parts suppliers are PURPLE and GREEN. These are for CARS. TRUCKS like OURS REQUIRE the BLACK banded modulator, likely from a transmission shop or dealer. This is regarding the mid/late 80's models, maybe more... Id venture to say any C6 with a slip in modulator. Again, PURPLE and GREEN are NOT the correct units to use, BLACK is the intended modulator as was designed for TRUCKS; by MyFullSize (Andrew)

Or Clogged filter.

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Yo, part deux,

c6exp.gif

NOTE: If automatic transmission fluid is present in the vacuum side of the vacuum modulator  or in the vacuum hose, the vacuum modulator's diaphragm is leaking and must be replaced. by Ford

C6 Description & Operation, Adjustments, Diagnosis & Testing (partial), Disassembly & Assembly, Parts Break-Out Diagram, Hydraulic Control System Diagram, Removal & Installation & Specifications @

http://web.archive.org/web/20090529064029/http://www.thedieselfiles.com/Ford/C6%20Automatic%20tranny.pdf

 

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Thanks 

I pulled the vacuum hose of and got 16-17 inches of vacuum and a small stream of fluid 

The only way for fluid to get up there is through the (broken) modulator, Correct? 

 

Is this the right replacement ? 

https://www.ebay.com/itm/FORD-C-6-TRANSMISSION-VACUUM-MODULATOR-BLACK-STRIPE-PUSH-IN-1973-UP/253596332726?hash=item3b0b84f2b6:g:8csAAOSw0vBUhNhF

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Yo diy,

Yes if  fluid is in vacuum line, replace modulator.

Yes, black striped modualtor.

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thanks miesk, i tried picking one up local, but you know how that goes 

ended up ordering one online, should be here friday 

i also noticed there isnt a kickdown linkage on the truck so i ordered a lokar style cable aswell 

 

 

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 I'm not sure if my 87 should have a cable or a linkage, but since all of if is missing (except for the lever on the transmission) I figured putting in an aftermarket cable would be the easiest

Specially since I'm also running an aftermarket intake and carb 

 

I got a lokar kit on my duster, and I'm running a Holley on that as well, so it should be pretty simple to get that hooked up

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Yo diy,

Lokar should be able to give you tips.

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been out of town for a few days, but i got back yesterday and got the modulator installed, and the kickdown cable in place

trying to get the kickdown set up, it looks like the shaft the the kickdown lever (on the transmission side) is mounted on spins 

ill have a closer look as soon as i get a chance, but that doesnt sound right, does it?

 

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mhh, ill have to look into that later 

right now, im not registering any fluid on the dipstick, i guess it got sucked through the modulator into the engine ?

 

what does this take, just off the shelf ATF?

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16 hours ago, diymirage said:

mhh, ill have to look into that later 

right now, im not registering any fluid on the dipstick, i guess it got sucked through the modulator into the engine ?

Yes! Suggest pulling a plug to check for contamination

what does this take, just off the shelf ATF?

transfluidchart.jpg

The C-6 also has a very large fluid capacity at 24 pints, including the fluid in the torque converter. Ford used type FA transmission fluid, which was specific to Ford transmissions until mid-1977 when C-6 transmissions were converted to Dexron/Mercon late in that model year. The easiest way to tell what fluid you should be using is to check the dipstick. The stick will reference either the FA specified fluid or an M2C138-CJ specification, which is Ford's designation for Dexron/Mercon.

 

 

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Yo,

I got hung up in a 5 minute lag here.  Any issues on your end diy?

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thanks miesk 

i checked with the guy that rebuild the tranny last year, he said merc/dexron so i added about 3 quarts of that and all seems well 

ill let het settle for a while and check again next time i take her out 

 

 

as far as the site goes, all is running smooth here  

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