C-6 trans troubles
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Trailering
Joined: Jan 2022
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C-6 trans troubles
I have a 1979 Ford Bronco I just swapped a 460 into and rebuild the transmission and transfer case while I had them out. I then drove it around some and after about 80 miles it stopped driving forward but would drive backwards so I pulled the trans back out and found the forward clutches were smoked so I figured I had the tolerance to loose and it had slipped so I replaced those clutches and set the tolerance tighter then I put it back in and now it still won't go forward but will go in reverse. Does anybody know what the problem might be?
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Joined: Apr 2004
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The hazards of DIY transmission rebuilds.
Unless we have the transmission in front of us, all taken apart for inspection, it's going to be hard to determine other than the general "you made an error" comment.
Did you clean out the cooler? New converter or the old one?
Link to a manual if you need it:
https://www.ford-trucks.com/forums/1...l#post16811346
Has a video, and other info:
https://www.ford-trucks.com/forums/1...uild-tips.html
Unless we have the transmission in front of us, all taken apart for inspection, it's going to be hard to determine other than the general "you made an error" comment.
Did you clean out the cooler? New converter or the old one?
Link to a manual if you need it:
https://www.ford-trucks.com/forums/1...l#post16811346
Has a video, and other info:
https://www.ford-trucks.com/forums/1...uild-tips.html
Cargo Master
Joined: Nov 2009
Posts: 2,364
Likes: 118
From: starship enterprise
sounds like you might have a rolled or torn seal ring, this can be air checked in frame, also the return spring also the check ball in the drum also the stator support seal rings also low pump pressure. I would like to follow up with asking for a control pressure verification, also temp could be helpful if it is building heat for some reason or another and then check band adjustment and condition, possibly too tight or incorrect strut or lever. Now, if it has reverse It might have 2nd if you lock it into 2 and it goes then let us know.
Cargo Master
Joined: Nov 2009
Posts: 2,364
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From: starship enterprise
that is a little low, pressure at -0- governor rpm calls for 138-156psi at 6000' above sea level (where I am) in forward and 158-176 psi at sea level in forward so the forward is low but your reverse pressures are in range for sure. That would lead me to believe the pump is not weak, but there is an issue preventing the pump from building pressure, and that could be in the modulator the valve body or a seal leak. Low pressure in 2 is band related. if that molded servo is not fresh and gotten hard, might be losing a seal, but that does not explain the 1 low reading, so compound issue or modulator or valve body or ??
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Trailering
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Cargo Master
Joined: Nov 2009
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From: starship enterprise
I mean, all depending on several aspects. Not necessarily. That is a control pressure check, once the vacuum drops under acceleration and the governor signal starts to come in that pressure changes. If your drops even more, or overcomes a leaky seal and can't stay engaged under load then it may not move. Have you checked all your adjustments? maybe the band is not fully releasing (adjustable) and trying to engage 2 gears, did you replace the steels on any of these repair attempts? or just clutches? Warped steels can cause a lot of problems. Did you check that?
Mountain Pass
Joined: Nov 2022
Posts: 226
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From: South East Kansas
Did you pressure check the clutch packs when you rebuilt the trans? Each of these packs and be air tested with the valve body out of the transmission.
If the clutches hold pressure, then there is an issue with the valve body.
If the clutches hold pressure, then there is an issue with the valve body.
Cargo Master
Joined: Nov 2009
Posts: 2,364
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From: starship enterprise
atleast you changed the steels. For the 4 or 5 time, its a good idea to air pressure each circuit and listen for a solid thump engage and a good thump disengage. If you choose to not do this, then next is did you measure the clutch packs with a feeler gauge? do you own a feeler gauge? What were the feeler gauge results from each clutch pack? Was it "in range?" tight? Loose? I have had a few c6 drums that had soooo much tolerance I actually had to add an extra friction disc in the bottom and double stack the first or it was .200" freeplay and that is toooooo much. steels are made cheaper nowa days I guess and frictions are a little thinner too, add a couple thou on each layer and a originally thin reaction plate and a slightly worn snap ring groove and a happenstance thin snapring, you now have lost .100" respectively and the tolerance is never going to be able to allow positive engagement; I dont care how much pressure you give it. Again, how is the band adjustment?
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Trailering
Joined: Jan 2022
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The forward clutch was at .040
and the high reverse clutch was at .048 if I remember correctly.
I don't know what the other set of clutches was at.
On the second gear band I tightened it to 10 ft/lb and then loosened it 1 1/2 turns.
I don't mind taking it apart and air testing it I will do that when I get a chance to work on it again.
and the high reverse clutch was at .048 if I remember correctly.
I don't know what the other set of clutches was at.
On the second gear band I tightened it to 10 ft/lb and then loosened it 1 1/2 turns.
I don't mind taking it apart and air testing it I will do that when I get a chance to work on it again.
5th Wheeling
Joined: Jan 2010
Posts: 32
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My experience with a C6 in my 72 Torino with a 429. I rebuilt it. Took of shifting manually, 1st no issue, 2nd no issue 3rd it locked up. Pulled back to 1st no issue, same for 2nd and again 3rd locked up. Had reverse but no drive.
Come to find out the one way sprag inside and the last thing that comes out had all the rollers on one side. Just something to think about if you haven't already.
Come to find out the one way sprag inside and the last thing that comes out had all the rollers on one side. Just something to think about if you haven't already.