1991 Ford Explorer Transmission Woes

[andy_brooks]

I've got a 1991 Ford Explorer with an automatic transmission that can't seem to stay in overdrive on the freeway. I bought the truck used w/ 40k miles, replaced the transmission at ~50k miles, and am now at 120k miles.

Here's what happens:

When driving on level road at 60-65mph and rpms at ~2600, the engine sometimes kicks down to third gear, bumping the rmps to 3100+. The check engine light flashes when this occurs. If I let off the gas a bit when it downshifts, wait a few seconds and then accelerate again, it goes back to overdrive.

Any ideas? I do live in the hills, but never drive the hills at high speed, nor have I ever towed anything. The truck's currently in the shop, so your help and guidance is greatly appreciated.

Andy

abrooks@eccompany.com

 

[tac0meat]

andy, when im cruisin at high speed say 90+ (2400rpm)on level ground if i barely move the throttle down a little further it will downshift. i was seeing a thing for chevy p/u that keeps the tranny from downshifting at half throttle for high speed cruising. the point is is at that rpm just a slight nudge on the gas might make the tranny think you are wanting to pass/accelerate and it downshifts to go faster.

 

[Josh Adams]

Hey, I had a similar problem and I had gotten prices of trannies and how much trouble it would be to change it out, and then I went and took it to a mechanic and he did a dyagnostic check and told me that it didn't show up on the computer. He also said the only thing he could not check was the MAS, and told me that it was more than likely the problem. I changed it and tranny slipping in and out was gone. It is a far fetched idea but it beats spending $700 for a new tranny. I also read that the voltage regulator on the alternator could be bad, so I changed it as well. This may or may not work. My MAS went out at 104,000 miles, so it would probably be a good idea to change it out anyways.
Good luck!

 

[Goober]

tacOmeat, what gears are you running? 90mph a@ 2400rpm is a little hard for me to imagine, but I am curious.

 

[Hoppy]

Try checking your Throttle position sensor, this happened to me until the transmission would not stay in overdrive. then the check engine light came on, and gave me the code on the TPS. I changed it, and perfect, no problems since.

 

[scott]

T.V. cable...

on a '91 the T.V. cable dictates shifting charateristics. Re-adjust it and check it out then.

 

[tac0meat]

goober, i run either a 3.07 or 3.08 i cant remeber which yeah i have no acceleration or raw power but i like the fact that i get my best gas mileage at 75+ but i cant afford a regear(im two wheel drive so its not that big of a deal to me). did you get regeared? cause 2600rpm at 60-65 seems really high(thats what i run if im in third).

 

[Goober]

Wow, a 3.08, no wonder you are running that low. I bet stop & go traffic kills you( mileage). Andy_brooks is the guy who posted those rpm/mph, but mine are close to that. At 65mph mine is dead on 2500rpm with 3.73 gears. As soon as I can I plan on getting 4.10's and that will get me down where it was before the lift, tires,etc. I think I was running 2000 rpm's at 65mph then, something around there, can't remember.

 

[ltschoop]

I am writing for a similar problem, perhaps the same thing. I have a 91 XLT. When crusing down the interstate around 70 if I go up a hill or stay level nothing unusual happens. If I climb a hill after I get over a crest and start down either it down shifts or the lock-up torque converter disengages. I go from about 2500 RPM to 2800 RPM. It seems to me to act more like the lock-up is disengaging, when I made it downshift it went to around 3100 RPM. Around 10 seconds later it kicks back in and I drop back to 2500 RPM again. It is weird to get this going down hill. I got it to do this with and without cruse control on. I have not done any major troubleshooting, but will try to get codes tomorrow. Josh and Hoppy, I do not know why the Mass Air Sensor or Throttle Position Sensor would have an affect on this, how close was this to your problems? Anyone else seen anything like this?
Schoop

[Edited by ltschoop on 09-22-2000 at 07:46 PM]

 

[Hoppy]

My experience with the TPS going out was there were bad spots in the sensor. What happened was I was driving down the highway at about 110 kmph (70 Mph) in cruise control and for no reason the tranny unlocked the torque convertor, shifted into third and then automatically went back into lockup and overdrive. After doing this about 3 or 4 times the check engine light came on and then would not shift into overdrive or lock up. I ran the codes and the TPS was sending a bad signal. I replaced it and the problem was gone.

I just wonder if it is because you are accidentally tapping the brakes or letting off the gas too much to coast down the hill. These two things will make the truck unlock the convertor and downshift into third as well.

Hoppy