Not sure of type of tranny this is but its in a F150 4wd, automatic with overdrive and about 120k miles, unsure of the maintenance history. Anyways, we have been using it to haul a 23' trailer that last couple summers, not long trips but somewhat mountainous. Occassionly when driving unload on level ground at various speeds, the tranny will shift down a gear then back up. Fluid level is good, smells non-burnt and is a nice red color. It doesn't happen much and really doesn't bother me much but thought I'd ask someone if this is something to be concerned about?

 

How is your speedometer working? (steady or bouncy)
ABS light? (on some times)

 

is it idleing high as in higher then usual

 

speedo is working normal, occassionaly the abs light has come on in the past but mainly in the cold winter days.

And Idle is normal.

 

well that ruled out the tps sensor then

 

I have the same problem in my 94 with the inline six , it has the E40D 4-speed , almost 159,000 miles. Only mine slips in and out of overdrive , & sometimes it just shifts REALLY hard ( KA-BOOM!! lol ) Sometimes through out all gears , sometimes it won't do it at all. Anyways , I'm interested if you find out anything about this stuff , I'm looking for another tranny before winter.... just in case.

 

It sounds to me like it's acting normal. Regardless of whether the trailer is empty, the engine is under more load than normal, and as such has to work harder to maintain speed even on level ground. Even if you're holding a steady foot on the gas pedal the trailer is working the engine and slowing it down, so it has to downshift to maintain speed occasionally. And do you have an overdrive override switch? If so make sure it's on so you're not pulling in overdrive. But if you're really concerned, see the top post on this board about how to pull codes and see what you come up with- that's the first step in making a diagnosis as the tranny shifts based on what the computer is telling it to do. Pull codes and let us know what you find.

Sounds like a sensor problem to me [unless this is a manual tranny you're talking about]. Once my MAP sensor went bad and my truck shifted really hard from 1st to 2nd and from 2nd to 3rd. Once I replaced it the shifting smoothed out. Basically, the MAP was sending bad info to the computer, so the comp was trying to compensate for conditions that didn't exist. Like straightsixer, I recommend you pull the codes [see the top post on this board if you don't know how] and see what you come up with, then report back to us.

 

If it's not a sensor check real good for vacuum leaks.

 

If it's not one of your sensors, check real good for vacuum leaks.

 

Thanks guys , I have an extra MAP sensor on another truck that had the 300 in it , so I'll try swapping that one in and see what happens. I think maybe my shift cable to the tranny may be out of adjustment also. When it's put in drive the needle stops on the far right of the drive/overdrive letter instead of being in the center of it & I think there is a sensor on that linkage too on the tranny. I guess I'll just have to try one thing at a time.

 

Occassionly when driving unload on level ground at various speeds, the tranny will shift down a gear then back up.

Happens going over say 45mph? Dropping out of TCC lock up then back in again, would feel like a down shift but its not a shift.

Low or drop in engine vacuum, faulty TPS or VSS.

 

I replaced the MAP sensor with one from the parts truck & the dropping out of overdrive problem is gone now. Still shifts hard sometimes from 1st - 3rd , but glides into overdrive and stays there. I haven't tried adjusting the linkage yet or the sensor on the linkage. Just happy it's staying in overdrive!! Thanks for all the helpful suggestions fellas!!