tranny question?
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Elder User
Joined: Mar 2009
Posts: 862
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From: eastern shore,MD
tranny question?
yesterday i was driving trough a little town, speed limit was 25, my truck could not seem to find a gear that it wanted to be in. keep shifting back and forth. did this about 3 times then stopped. went to friends house check fluid level, it was fine. fluid was nice and red. tranny temp was around 125. left his house it did it a couple more times then stoped. been acting fine all day today. the fluid was changed about 5 months ago. do you guys have any ideas, should i worry or not. really dont want to put a tranny in right now
Senior User
Joined: Aug 2004
Posts: 327
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From: Los Angeles
Mine does that at 35mph. I think it just can't quite figure out which gear it should be in. Once it downshifts there's not enough load to keep it down, but when it upshifts it decides there's too much load and needs to downshift. I currently (but not for long) have the Hypertech tune with transmission program installed. I know that particular tuner causes it to downshift from 4th to 2nd and then back up to 3rd. I've always assumed these are its quirks. It'd be nice if mine did it at 25 instead of 35, since most residential streets around here have a 35 mph speed limit. 
Senior User
Joined: Aug 2004
Posts: 327
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From: Los Angeles
Hey Josh, is your third brake light out? Mine was out since I bought the truck. I found out that a dead bulb in the high mount stop light prevents the torque convertor from locking up before 30% throttle. Having replaced the bulb, the transmission no longer fluctuates between the two gears.
Figured I'd post this as a follow up for anybody else.
Figured I'd post this as a follow up for anybody else.
Logistics Pro
Joined: Jun 2005
Posts: 4,243
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From: AZ
???? Are you certain of that? If so, someone at Ford needs to be pistol-whipped
Hook it, I'll pull it.
Joined: May 2007
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From: Grand Lake, La.
Laughing Gas
Joined: Feb 2004
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From: Leander Texas
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Logistics Pro
Joined: Jun 2005
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From: AZ
Look at this thread, post #8 and #14. https://www.ford-trucks.com/forums/2...-me-crazy.html
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Hook it, I'll pull it.
Joined: May 2007
Posts: 15,037
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From: Grand Lake, La.
Good link Izzy.
Laughing Gas
Joined: Feb 2004
Posts: 822
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From: Leander Texas
When my old mans mechanical diode went out, I took a look at his non working 3rd light for the heck of it. You could plainly see that it had filled with water and shorted out. Obviously fixing it did nothing for his trans issues. I don't recall hearing of anyone actually having this problem, but I guess it does exist.
Logistics Pro
Joined: Jun 2005
Posts: 4,243
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From: AZ
I had my high mount stop light bulb out for several months. Replaced the bulb and saw no difference whatsoever. Then again, I didn't have any issues with the shifting either.
When my old mans mechanical diode went out, I took a look at his non working 3rd light for the heck of it. You could plainly see that it had filled with water and shorted out. Obviously fixing it did nothing for his trans issues. I don't recall hearing of anyone actually having this problem, but I guess it does exist.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,734
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From: SE Florida
There was a relationship between the brake lights and the torque converter clutch locking on the OBS trucks. By 1999 that problem was fixed.
I have no help on the shifting problems. When there is a tuner involved I don't know what's going on in the PCM.
I have no help on the shifting problems. When there is a tuner involved I don't know what's going on in the PCM.