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Shifting Problems

 
  #1  
Old 06-28-2004, 01:41 PM
Dave Tag
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Shifting Problems

I have a 99 F350, Power Stroke, 4X4, with automatic transmission that was manufactured in February of 1999. I have a shifting problem and serious lose of power when the outside temperature rises above 90F. This only occurs when it's hot outside. I can drive the truck across Texas in March and never have a problem, but I can't drive it across town in August. The truck has 195,000 miles on it now, but this has been a problem since it hit 40,000. When the outside temperature is above 90F, the engine will run to a much higher RPM before shifting, with a huge lose of power. The shifting is very similar to the way the truck shifts first thing in the morning (if you don't let it warm up correctly)....This occurs most commonly when it shifts from 1<SUP>st</SUP> to 2<SUP>nd</SUP>, but as the outside temperature rises it will also happen when shifting into higher gears. It gets even worse when I'm pulling a load. I have had the truck in various Ford dealers and reputable repairs shops, and no one can seem to figure out what the problem is....They've had it hooked up to the computer while it was acting up, and got no error messages. I've had the truck from day one, the transmission has been flushed multiple times, the torque converter and transmission cooler have been changed....Has anyone heard of any Superduty acting like this. Any advice is appreciated...
 
  #2  
Old 06-28-2004, 06:19 PM
U_B_LO
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I think I've read where diesels have vacuum accumulator containers for working the shifting apparatus, kind of like the way the manifold vacuum on gasoline engines would control the modulator valve to allow shifting. It alsmost sounds like this type of problem. What the correlation with temperature is ???? Someone on the forum should be able to help.
 
  #3  
Old 06-28-2004, 07:04 PM
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Just had to put a tranny in my 97 with similar symptoms. Had to rev up way too high to get into second. It would actually shift to second better if I ran it up in first, then backed off the throttle, then eased back into it. My problem however came on strong when it did start to happen. No way I could have made it another 1,000 miles, much less 150K like yours.
I would think about inspecting / replacing the valve body. Could be anything from a crack to a foreign object.
As with most things, it's probably something simple, but it's a matter of finding it. Good luck.
 
  #4  
Old 06-29-2004, 02:04 AM
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One of the guys at work had the same problem... apparently there is a tube that runs off the exhaust manifold up to a sensor on the front of the motor right next to the heater hose. what this sensor does is it reads the amout of load or back pressure from the exhaust and helps you tranny decide when to shift... the metal tube cloggs /cokes up right at the sensor... the dealer replaced both the tube and the sensor (under warranty) ... he says his tranny shifts great, he has better throttle response, and is getting 3 more mpg's.

I pulled my sensor off and it was coked up too... I shot a little wd40 down the tube and picked the crud out of the sensor. with the sensor off I started my truck, had one of the guys rev it up while I watched. It blew crap everywhere.
I put the sensor back on and it seems to shift smoother and there doesnt seem to be that little lag between gears. I dunno if its just my imagination or not, but you can try it for yourself...

tommy
 
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Old 06-29-2004, 09:07 AM
Dave Tag
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Thanks for the info guys.....Tommy, I'm going to give your theory a try today. It just blows my mind that it only acts up when the outside temperature is above 90F. I'll let you know what happens.

Thanks,
Tag
 
  #6  
Old 06-30-2004, 03:42 PM
Dave Tag
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Angry

Well, there is nothing wrong with the tranny....They think it's a Fuel Delivery problem, or something wrong with the computer....But again, I've never been able to get an error code.
 
 


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