C^ Transmission
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C^ Transmission
I have a 1986 F250 w/351W 4x4 w/c6 xmission.
Recently on a cold morning I started the truck and let it run to warm up. When I drove off in drive the transmission would not shift from low gear. I can shift into second manually and then back to drive; it will then be in second.
After shutting down the engine and re-starting it runs extremely rough, after driving for awhile the rough idle goes away, but then it idles very fast, app 1500/1800 rpm.
Question?; Does any one know what causes this to happen.
Could it possibly be a vacuum line.
Recently on a cold morning I started the truck and let it run to warm up. When I drove off in drive the transmission would not shift from low gear. I can shift into second manually and then back to drive; it will then be in second.
After shutting down the engine and re-starting it runs extremely rough, after driving for awhile the rough idle goes away, but then it idles very fast, app 1500/1800 rpm.
Question?; Does any one know what causes this to happen.
Could it possibly be a vacuum line.
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C^ Transmission
If it is a c-6 tranny, check to see that the modulator line is not disconnected at the engine and modulator. If it is still on and no leaks then pull the line off at the modulator and see if it has fluid in the line. If so, replace the modulator.
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C^ Transmission
Thanks for the info. Yes it is a C6. I checked several vacuum line at the engine and carb. I don't know what the modulator looks like or where it is located.
Can you provide some additional information.
Thank You
Can you provide some additional information.
Thank You
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C^ Transmission
The modulator is located at the rear of the trans just to the right of the tail housing right above the pan. It is about 2 inches in diameter at the widest point and then tapers to about 1 inch or so. The vacuum line attaches directly to the rear of it.
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C^ Transmission
You were right on the money! A vacuum line was disconnected. Not where you would expect. Disconnected at the intake manifold. This point was a source for the heater controls and the transmission. After installing the line the transmission slips from 1st to 2nd and from 2nd to 3rd.When I removed the original valve it did have oil in the line and valve. Since the problem was a disconnected line can this part be cleaned.
Still a little bit of a story; turns out there are three types of modulator, one with a purple mark $23.00, black mark $34.00 and no mark $158.00 (dealership price). That's right, I have the one with no mark. It's a high altitude version. I tried one of the others and it would'nt work.
Still a little bit of a story; turns out there are three types of modulator, one with a purple mark $23.00, black mark $34.00 and no mark $158.00 (dealership price). That's right, I have the one with no mark. It's a high altitude version. I tried one of the others and it would'nt work.
Post Fiend
Joined: Jan 2001
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From: Springfield, VA
C^ Transmission
I have an '85 F-250 2wd with the 460 and auto tranny (not sure which). The truck has been sitting for a while due to gas tank problems. Well, I got that fixed, now the truck won't move. The engine runs, and it seems to shift into all of the gears easy, but it just won't move. It's almost like it's stuck in neutral or park. I have talked to several people and they told me that that the tranny has "bands" that are stuck and that I should pour some kerosene into it, and work it through by running the engine and shifting through the gears. Does that really work as far as getting the bands un-stuck? This truck was given to me, and I really don't want to pour a ton of money to get it going, so I'm looking for a cheap, but good fix.
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C^ Transmission
A C-6 only has one band that engages for 2nd gear. How long has the truck been sitting? Was the trans working when parked? Probably wouldn't hurt to drop the pan and change the fluid and filter and see what shape the fluid is in.
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Post Fiend
Joined: Jan 2001
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From: Springfield, VA
C^ Transmission
It was sitting for about 6 years. It was a daily driver when parked. When I towed it out of its spot, I put it in neutral and it rolled easily. I put it in park and tried to move it to see if it was stuck (after I couldn't get it to drive), and the rear wheels were locked, like they should have been. I haven't had a chance to drop the pan and change the fliud and filter. That was going to be my next step, I just wanted to see if anyone has heard of the kerosene trick before I changed the fluid, as I really don't want to change the fluid several times if I don't have to.
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C^ Transmission
[font size="1" color="#FF0000"]LAST EDITED ON 30-Jan-01 AT 12:47 PM (EST)[/font][p]I wouldn't put kerosene in it. I have not heard of this being done. It could loosen the adhesive on your clutch discs. You might try starting it and going back and forth from drive to reverse without revving the engine. Just let it idle and see if it works itself out.
Post Fiend
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From: Springfield, VA
C^ Transmission
Ok, I did some checking on this thing. With the truck running, I have to pretty much floor it to make it move either forward or backwards. I didn't try this before, because I didn't think of it. Realizing that it is a c-6, I haven't gotten under the truck to check the vacuum line or see of the modulator is bad (read my Haynes manual last night!!). Could the modulator possibly the reason it doesn't move that much? Also the Haynes book says that if the band is not adjust properly, it could possibly make it do that. I really don't have that much experience with auto trannys, so any help or insight would be helpful.
thanks,
Karl Jett
thanks,
Karl Jett
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C^ Transmission
The band only is used to shift to 2nd gear. If you take the band clear out it will still have forward and reverse. My guess is you have a valve sticking based on what you have told so far. Did you check the fluid level with the engine running? Is it full?
Post Fiend
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From: Springfield, VA
C^ Transmission
It is full, really dirty but full. A valve sticking? Other than changing the fluid and filter, I really don't have that much experience with auto trannys. I will try to check the modulator and vaccum line this weekend and change the fluid and filter. If you think it is more than that, I guess I'll be pulling it and sending it off to be repaired. I will keep you posted as to the solution. Thanks for the help.
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C^ Transmission
sounds like your front pump it fills your torq converter and control all the clutches how much pressure they get so on and so forth sounds like you might have a relief or bypass stuck
DO NOT use solvents they can soften seals and ruin them much like putting motor oil in place of brake fluid bad news unless you have played with auto trannys or have lots of time patience and a good shop manual send her off
P.S. if you get it going write back would love to be wrong and know what you did
DO NOT use solvents they can soften seals and ruin them much like putting motor oil in place of brake fluid bad news unless you have played with auto trannys or have lots of time patience and a good shop manual send her off
P.S. if you get it going write back would love to be wrong and know what you did
