Trans Free Wheeling
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Trans Free Wheeling
I have a 99 F-250 SD with a 4R100 transmission. When going about 35mph and in 3rd gear, if I take my foot off the gas, the rpms drop to about 800. Then when I step on the gas, the rpms increase they match the speed of the truck. Thus the transmission is free wheeling in third. This does not happen in overdrive or in 2nd. What could be causing this????? Don............
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It just does it in 3rd. In addition, when going about 55 and in overdrive, if I push the overdrive lockout button on the shift, the transmission shifts to 3rd. But if I take my foot off the gas, the rpms drop to 800. There is also a strange thing that happens when going about 55 and in overdrive. If I tap or push on the break pedel, the transmission shifts to 3rd and then right back to overdrive. I have taken it to two transmissions shops and they could not find out what is wrong. They said that there were no codes showing on the computer. Something is not right......
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If you didn't get the truck new, is there a chance someone put a brake controller on it? I see no reason why the brake pedal should make the tranny downshift, unless there is a brake controller in it and it's trying to slow down the truck.
Also, if someone DID put something of that sort in the truck, they may also have a TC lockup full-on/full-off switch somewhere. Meaning, they can lockup the TC when they want, or unlock it when they want. Depending on how they wired it in, the connections may be failing and the tranny is loosing control of the TC.
Also, if someone DID put something of that sort in the truck, they may also have a TC lockup full-on/full-off switch somewhere. Meaning, they can lockup the TC when they want, or unlock it when they want. Depending on how they wired it in, the connections may be failing and the tranny is loosing control of the TC.
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Are you sure that the brake pedal makes it shift to 3rd? Pressing the brake pedal is supposed to unlock the torque converter.
As for going to idle speed, your coast clutch isn't working. It could be a wiring problem to the coast clutch solenoid, or a bad solenoid, or the coast clutch itself has failed. I'd check them in the order I listed them.
As for going to idle speed, your coast clutch isn't working. It could be a wiring problem to the coast clutch solenoid, or a bad solenoid, or the coast clutch itself has failed. I'd check them in the order I listed them.
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Originally Posted by donks
I have a 99 F-250 SD with a 4R100 transmission. When going about 35mph and in 3rd gear, if I take my foot off the gas, the rpms drop to about 800. Then when I step on the gas, the rpms increase they match the speed of the truck. Thus the transmission is free wheeling in third. This does not happen in overdrive or in 2nd. What could be causing this????? Don............
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Yes it is a diesel. But I have two friends that have F-250 diesels with the 4R100 transmission. Neither of the friends trucks do the free wheeling trick. You may be refering to the fact that diesels do not have as much compression to hold them back as compared to gas engines. Don.............
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My 99 350 Crew PSD is in the shop getting a new TC and Tranny. A result of the symptoms above. I had it in the shop a couple times and nobody could figure out what was wrong. In the end it was the TC failing and it tore up the tranny.
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Originally Posted by donks
You may be refering to the fact that diesels do not have as much compression to hold them back as compared to gas engines. Don.............
Diesels are very HIGH compression. The problem is they do not have a throttle plate like a gas engine, so the intake is wide open at all times. Engine braking is from the vacuum in the intake... on diesels, they have to put a butterfly in the exhaust to get engine braking.
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Casey, You were right. Took the truck to AAMCO and they pulled and inspected the transmission. Sure enough it was a bad coast clutch. Thanks for the help. Don............
QUOTE=Casey]Are you sure that the brake pedal makes it shift to 3rd? Pressing the brake pedal is supposed to unlock the torque converter.
As for going to idle speed, your coast clutch isn't working. It could be a wiring problem to the coast clutch solenoid, or a bad solenoid, or the coast clutch itself has failed. I'd check them in the order I listed them.[/QUOTE]
QUOTE=Casey]Are you sure that the brake pedal makes it shift to 3rd? Pressing the brake pedal is supposed to unlock the torque converter.
As for going to idle speed, your coast clutch isn't working. It could be a wiring problem to the coast clutch solenoid, or a bad solenoid, or the coast clutch itself has failed. I'd check them in the order I listed them.[/QUOTE]