Irradic shifting problem
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Junior User
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Irradic shifting problem
Have 93 F250, 7.5 auto. The trans wants to shift a lot at highway speeds, running 3k rpm then up shifting briefly before downshifting back up to 3k. This is unloaded, flat roads. Probable cause is the p/o removed the column shifter an put a homemade floor shifter, so there is no overdrive cancel button. this doesn't happen all the time, about 40% of the time. Also, where would I plug into to install an O/D switch on the dash so I can procrastinate on buying all the linkage and shifter parts?
Lead Driver
Joined: Mar 2006
Posts: 6,259
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From: IL
Running flat highway, @ 3K RPM is what?? 60mph?, I wouldn't think it would be shifting back into passing gear unless you were feeding it the gas pedal. Or are you saying that it's in drive the n shifts to OD then back to drive? Either way, IMO if it's shifting back and forth like that and you're running flat and empty, Id' say you have a problem with the shift solenoid for the OD, but I'm not that familiar with the auto tranny's. I had 1 an E4OD on my 94 F350 7.3IDI and it cost a crap load of money to fix the (mechanic called them coil packs) in the trans).
Lead Driver
Joined: Aug 2006
Posts: 5,670
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From: Sand Lake, MI
Yea its not getting into final drive or its failing to lock the TCC, is running in Drive locking/unlocking TCC never going into OD.
Needs the button to complete the circuit for OD to be possible, it's not having the button if the wires to it where not tied together, red-yellow and tan-wht, when it was removed = no OD.
Find those wires under the dash, tie them together if you find they are not already.
That coupled with running like crap/weak just not creating any power at all and or sucking air like its going out of style? 3K is near double what it should be highway speed.
Run the self test see what it tells ya too.
Needs the button to complete the circuit for OD to be possible, it's not having the button if the wires to it where not tied together, red-yellow and tan-wht, when it was removed = no OD.
Find those wires under the dash, tie them together if you find they are not already.
That coupled with running like crap/weak just not creating any power at all and or sucking air like its going out of style? 3K is near double what it should be highway speed.
Run the self test see what it tells ya too.
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Ill look for those wires. It has lots of power, except for the radiator leaking, the only other real prob is the trans. weather it is O/D or just 3rd, when it acts up it is constantly shifting like im passing, and for the most part when it is acting up, it mostly stays in the lower gear most of the time.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
Ill look for those wires. It has lots of power, except for the radiator leaking, the only other real prob is the trans. weather it is O/D or just 3rd, when it acts up it is constantly shifting like im passing, and for the most part when it is acting up, it mostly stays in the lower gear most of the time.
Could be related to throttle position sensor and or perceived ground speed, failing/faulty POSM or dirty VSS or any combination of.
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Thanks. I am not up to speed on all these sensor abbreviations, what is the POSM or dirty VSS, and what is the correct way to test them? I haven't been on the highway since then, but today I did notice that the makeshift shifter had the gear select between where D and 2 are and it was acting a little funny then and when I readjusted the shifter it was running fine. Hopefully it its something easy and stupid as that. I do have to check for those wires because I don't think its going into O/D. Is this transmission a 3sp+O/D+lockup, or is the lock up the 4th gear O/D?
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