Transmission hunt between 3rd and 4th

[naturlm]

My 95 Explorer XLT transmisson is hunting up and down between 3rd and 4th when in overdrive and when traveling at steady speeds on flat highways between 50 and 70 mph. The up and down shift occurs every few seconds and rpm bounces up and down approx 400 - 500 rpm at each up and down shift. If I take it out of overdrive, it stays in 3rd and the hunting discontinues. Vehicle shifts fine under acceleration in all gears and there is no hunting up and down between 1st / 2nd and 2nd / 3rd.

Check of transmission fluid shows it clean with no bad odor.

Could this be caused by a bad voltage regulator with the spikes in voltage effecting signals between pcm and transmission ? But why would it only effect overdrive ? What are voltage specs on regulator and can it be checked out easily some way with my digital vom ?

Any other thoughts / ideas as to cause or how to diagnose the problem ?

[BlitzKeg]

sounds like you need some transmission work=(

I'll get into depth later I'm at school and don't have time........
will post later srry

[wiesejt]

I had a similar problem with my '99 Explorer Sport a few months ago. The problem was with the solenoid attached to the tranny. I replaced it and now it runs great.

[naturlm]

Originally Posted by wiesejt

I had a similar problem with my '99 Explorer Sport a few months ago. The problem was with the solenoid attached to the tranny. I replaced it and now it runs great.

wiesejt,

Thanks for the tip. I have stared to do some reading to better understand how auto trannys work. Makes some logical sense to me, if the solenoid is sticking or not fully opening or closing when it gets the signal for computer to do so it might cause the up and down shifts in sequence at constant load. I have a few follow up questions...

Did your onboard computer diagnostic system engine error code light come on when your transmission was hunting up and down ? Just wondering, as mine does not come on during the hunting, and I think it should ?

If your onboard computer diagnostic system did have and register an error code is that how you identified the solenoid as the problem ?

I assume the solenoid you replaced was the one which activates the tranny torque converter lockup clutch ?

Is this something you yourself were able to replace or did you have Ford dealer or a non dealer tranny specalist repair type shop do it for you ? I am thinking to do it myself I have to drop the tranny pan, locate the solenoid, remove and replace it, replace pan, add new fluid, etc. I am also wondering yet..... if the problem could be in some other part of the electronic system controls ? maybe in one of the sensors feeding into the computer that helps computer make the decision whether lock or unlock the converter clutch ?

Appreciate any more info you can give,]

thks

naturlm

[wiesejt]

Well, I will try to answer you questions as best I can. You see, I am a computer guru. My Dad is the mechanic in the family and as he lives in the northeast and I live in Texas, it is not fesible for me to get him to do my car work. Forutnatelym my Mom has a great mechanic that is extremely fair and straight-forward.

In regards to the indicators, no I did not ever get any indication or code as to what the problem was. Personally, I was leaning towards a tranny gear with some damaged teeth. I took it into my Mom's mechanic and he concluded after 3 days of diagnostics and test drives that the problem had to be the solenoid. In fact, he said the tranny itself still looked factory new - no shavings or anything in the fluid.

I could not begin to answer the question of doing it myself since I had no idea that was the problem to start. I am certain it is possible to do yourself with the aid of a Chilton's or similar manual. Sorry I could not answer your question much better than that.

If you want to rule out the electrical system, the only way on these newer vehicles is by taking your truck in for a diagnostic, as I am sure you are aware.