C6 tranny problems ?
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C6 tranny problems ?
I seem to have a bind up or something going on with my C6, this happens in forward only, and from a stop. When this happens my engine seem to torque up and when the " bind up " releases the engine slams back on the motor mounts. I thought it was broken motor mounts at first ( I did find one )but they were replaced when I dropped in the new engine. I do plan on rebuilding the tranny when I get the truck out this spring, I was just wondering if anyone else has had this happen to them.
Laughing Gas
Joined: Jun 1999
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From: Banning CA
C6 tranny problems ?
Need a little more info, though it sounds like it is loosing hydraulic presure, either because it is low on fluid or something inside. Could you explain a little more as to what it is doing.
Dave
http://a2ztowing.homestead.com/a2ztowing.html
Dave
http://a2ztowing.homestead.com/a2ztowing.html
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C6 tranny problems ?
Dave, I don't how else to explain the problem, I have really racked my brain on this one. When taking off from a stop, as you pick up speed, and before the tranny shifts to second, you will feel the gas pedel sort of drop at the same time as you hear a "clunk", all I can come up with in my mind is something binding, like maybe a clutch pack, and than when it releases the engine drops back on its perch which explains the gas pedel movement. One more thing, when ever I drain the fluid, about 9 quarts comes out, I don't ever remember this happening on any other transmission I changed the fluid on, usually only 4-5 qt. were required. As I said before I plan on pulling the trans. in a couple of weeks, I need to fix a rear main oil leak anyway on the engine, but if you have any idea what it might be I would love to hear it, it would give me something to look for on the tear down.
Charley Emmons
1967 F100 SB
390 C6 auto
Charley Emmons
1967 F100 SB
390 C6 auto
Laughing Gas
Joined: Jun 1999
Posts: 903
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From: Banning CA
C6 tranny problems ?
This sounds like a motor mount or trans mount broken, allowing the engine and or trans to lift and then drop. It does not need anything to cause it to lift other than just trying to take off, since the engine and trans are tying to turn the drive shaft to move the truck, it will tend to tourque up. Check all the mounts.
Dave
http://a2ztowing.homestead.com/a2ztowing.html
Dave
http://a2ztowing.homestead.com/a2ztowing.html
Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
C6 tranny problems ?
I had the same binding problem on takeoff with my 91 F-150. The motor didn't lean over but those 300's seem to almost be a solid mount. It turned out to be worn clutch packs. Had the tranny rebuilt and everything was great. I feel my 390 tip over and the gas pedal drop when it shifts into second (shifts hard), but the motor mounts look good, but will still be replaced in a few weeks when the motor gets rebuilt. Open your hood, put your truck in drive and hold the brake and stomp the gas. If your motor leans way over change all three mounts (tranny). It would suck to completely break one.
Lead Driver
Joined: Nov 2000
Posts: 6,623
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From: Albuquerque
C6 tranny problems ?
Another possibility is the tranny tailshaft bushing. If it is badly worn the dirve shaft slip joint can bind as the rear end dips or rises and then suddenly release causing a "jerk". The slip joint spines could also be dry or worn.
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
1977 Ford F-100
400m/c6
280,000 miles
Stock on the outside
modified/rebuilt everything
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New User
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C6 tranny problems ?
Thanks for all the responses, I replaced both engine mounts and the trans mount, and it didn't make any difference. There is one thing I forgot( trucks been in storage too long) when I first start the truck, I feel the transmission wanting to creep, I even disconnected the shift linkage and manually put it park, and it still did it, this only happens after it has set for a while, like overnight. I never thought of the tailshaft bushing, I'll look into that as well, thanks
Charley Emmons
1967 F100 SB
390 C6 auto
Charley Emmons
1967 F100 SB
390 C6 auto
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Post Fiend
Joined: Feb 2000
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From: Brea CA
C6 tranny problems ?
Does the transmission creep while in neutral too? It sounds like the forward clutch is hanging up. I’d take it to a reputable tranny shop and have them check it out (not AAMCO).
Barry
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From: USA
C6 tranny problems ?
[font size="3" color="#191979"]
No, as the Forward clutch is used for all 3 forward gears. The only time it is not applied is in Neutral and in Reverse. The rearmost clutch is used for first and reverse, and the front clutch is used for high gear and reverse.
Does it "bind" up when you put the selector in first? How about second - does it start out in second gear like it is supposed to?
Art
No, as the Forward clutch is used for all 3 forward gears. The only time it is not applied is in Neutral and in Reverse. The rearmost clutch is used for first and reverse, and the front clutch is used for high gear and reverse.
Does it "bind" up when you put the selector in first? How about second - does it start out in second gear like it is supposed to?
Art
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Joined: Jul 1999
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C6 tranny problems ?
Charley, Does the driveshaft spline have enough free movement forward to handle the movement from the rear axel? Maybe your drive shaft is a bit too long. I saw this where a feller shortened a long wheel base frame to accomodate a short box but did not shorten the drive shaft enough. He fixed it right away, but if he had not, the constant pushing on the output shaft could have caused damage to the tranny.
Laughing Gas
Joined: Jun 1999
Posts: 903
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From: Banning CA
C6 tranny problems ?
OK forgetting to tell us that it starts in second and that it had been in storage for that long is a big factor. What you may have is several different problems. First I would add a trans stop slip, like Lucas or something simular, this will help free up any sticky valves inside the valve body, You may also have a sticky govenor or a bad trans modulator. The sticky govenor could be helped by the additive, the modulator you should replace.
Dave
http://a2ztowing.homestead.com/a2ztowing.html
Dave
http://a2ztowing.homestead.com/a2ztowing.html
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