Transmission Slipping periodically at highway speeds only?

[markcs]

Hello,

I have a 1996 Explorer XLT 4.0L with 140,000 miles. Over the past couple of months, I have noticed situations where my transmission seems to slip for a second and re-egage quickly, mainly while driving at highway speeds (55MPH or faster). I first noticed this only when it was in overdrive. However, now if I run w/o overrive, I started to notice it slip as well while driving in third, again only at highway speeds and the issue is starting to become more prevalent. If I drive around town at 45mph or slower the problem does not occur.

I should add that the check engine light is constantly on and I noticed the transmission fluid does need to be changed as it appears reddish brown.

I have seen threads where some transmission problems could also be caused by electrical problems. Since this issue only appears to occur at highway speed, could this be a possibility or does the fact that the fluid seems to be burnt that it may be time for the tranny to be rebuilt.

Any advice would be appreciated.

Thanks,

Mark

 

[markcs]

Just an update. I stopped by my local Auto-Zone store today and the store manager pulled the codes from the computer. The codes were P0141, P0171,and P0172. I have had the O2 sensors replaced previously about 90,000 miles and one other again at 130,000. He must of reset the computer because the check engine light is no longer on.

As far as the slipping issue while driving on the highway, the issue still exists. I decided to hook up a DVM to the battery to verify if the voltage regulator could be a problem. During the test, the reading remained beween 14.1V and 14.4V even when the slippage occured. Also noticed that there is no fluctuation in the tachometer either when it occurred.

I also should point out two other scenarios which have occurred previously on a less frequent basis.
At times when driving at highway speeds and I come to a stop light, when I pull out afterwards the transmission seems to start out in third gear. I normally have to manually shift it into second to get going through the intersection. I would estimate that this scenario occurs about once a month. Also I have noticed previously that while driving on a incline the transmission may shudder when it downshifts. Again these last two scenarios do not happen frequently but may provide some other indications as to the state of the transmission. Also another comment which I know I will catch #$%! about is the fact that the transmission fluid has not been changed in the last 70,000 miles.

Thanks in advance for any advice.

- Mark

 

[96eb96]

Just an update. I stopped by my local Auto-Zone store today and the store manager pulled the codes from the computer. The codes were P0141, P0171,and P0172. I have had the O2 sensors replaced previously about 90,000 miles and one other again at 130,000. He must of reset the computer because the check engine light is no longer on.

As far as the slipping issue while driving on the highway, the issue still exists. I decided to hook up a DVM to the battery to verify if the voltage regulator could be a problem. During the test, the reading remained beween 14.1V and 14.4V even when the slippage occured. Also noticed that there is no fluctuation in the tachometer either when it occurred.

I also should point out two other scenarios which have occurred previously on a less frequent basis.
At times when driving at highway speeds and I come to a stop light, when I pull out afterwards the transmission seems to start out in third gear. I normally have to manually shift it into second to get going through the intersection. I would estimate that this scenario occurs about once a month. Also I have noticed previously that while driving on a incline the transmission may shudder when it downshifts. Again these last two scenarios do not happen frequently but may provide some other indications as to the state of the transmission. Also another comment which I know I will catch #$%! about is the fact that the transmission fluid has not been changed in the last 70,000 miles.

Thanks in advance for any advice.

- Mark

Those codes point to a bad passenger side (bank 1) o2 sensor. The other issue with those 3 codes could be a bad/pinched wiring harness, so you can look under the truck for that.

Not changing 4R55E trans fluid in 70K miles is probably the worst thing you can do to your trans, especially the original Mercon stuff that is in the 96. That exceeds two normal service change intervals! Lousy fluid could explain all the erratic behavior you are having, and your filter could be loose or clogged. Not good. You could also have internal damage (worn bands or leaking valve body seals.)

First thing is DO NOT FLUSH. I think you have two options at this point. Leave it alone, you may have 200 miles or 20K miles left(unlikely). Second is to risk a fluid and filter service, which will replace 4 quarts of the fluid. This may clear up all problems or make it worse. Also, when you drop the pan you will see if there are any broken pieces or excess wear. Good luck.

 

[markcs]

Hello 96eb96,

Thanks for the reply and advice. I have spent some time examining the harness to this sensor but have not noticed any physical damage. I do know that the sensor in question was one of the original sensors that was replaced at 90K.

I also appreciate the advice not to flush and understand, from reading the other threads, about the consequences that could occur if this is performed on a transmission that has not been serviced propery in the past. However, given that I am unable to drive this vehicle at highway speeds in it's current state, I think I will take a chance and at least perform a fluid and filter service to see if it makes any difference. I have never worked on transmissions before so I am not sure if I will be able to notice any damage unless there are some tell tale signs laying in the bottom of the pan but I am willing to give this a try.

Again thanks for your help!

- Mark

 

[Pensa]

I would try changing the filter and see if that improves things. If it's been 70,000 miles since a fluid change I would assume it's been at least that long since the filter has been changed.

It would be nice if there was a drain plug on the tranny, but there isn't and it can be a messy job, but not all that difficult. Make sure to put the rubber O rings on the filter when you replace it and have about 5 quarts of tranny fluid when you do the change.

 

[markcs]

Followup:

First of all, this board has been a great source of info. Thanks to all, especially 96EB96 and Pensa for your advice on this issue.

I changed the fluid and filter today. Aside from the fluid being really dirty, I found no broken pieces or metal particles in the bottom of the pan. No visible build up. I cleaned the pan, added new filter with O rings, and 4 qts of Mercon fluid. Took it out for a test run but unfortuanately no change. Still only slips or hesitates periodically whenever at 55 MPH or faster only. Although there seemed to be a period for awhile where it did not slip, but it returned again near the end of my run (about 10mi). Since the fluid in the torque converter was not changed will it take some time for the new fluid to circulate through it? I am anticipating that since only half the fluid was changed I will eventually have to do this procedure again. Should I risk a flush at this point.? I am also wondering if the issue is with the torque converter itself.


Regarding the other issue. The check engine light came back on this week and only the 0141 code showed up this time. I am planning to replace the O2 Heater sensor tommorow ( behind the catalytic converter on the passenger side). I hear it is a real pain to get to the connector and I do not have the "luxury" of pulling a center console to gain quick access.

 

[96eb96]

Followup:

First of all, this board has been a great source of info. Thanks to all, especially 96EB96 and Pensa for your advice on this issue.

I changed the fluid and filter today. Aside from the fluid being really dirty, I found no broken pieces or metal particles in the bottom of the pan. No visible build up. I cleaned the pan, added new filter with O rings, and 4 qts of Mercon fluid. Took it out for a test run but unfortuanately no change. Still only slips or hesitates periodically whenever at 55 MPH or faster only. Although there seemed to be a period for awhile where it did not slip, but it returned again near the end of my run (about 10mi). Since the fluid in the torque converter was not changed will it take some time for the new fluid to circulate through it? I am anticipating that since only half the fluid was changed I will eventually have to do this procedure again. Should I risk a flush at this point.? I am also wondering if the issue is with the torque converter itself.


Regarding the other issue. The check engine light came back on this week and only the 0141 code showed up this time. I am planning to replace the O2 Heater sensor tommorow ( behind the catalytic converter on the passenger side). I hear it is a real pain to get to the connector and I do not have the "luxury" of pulling a center console to gain quick access.

Here are some more options:

1)Try the button on your shifter stick. It will lock out overdrive and you can certainly drive this way with no issues. If it solves your problem you narrowed it down to an overdrive issue. Look at the forum stickies on transmission band adjustments. It must be done very precisely, and be sure to set your parking brake/chock wheels if you remove any linkages! Essentially your overdrive band (think brake) may be out of spec and not holding the drum, and letting it slip.

2) I don't suggest a machine flush unless you have a brand new trans. Even then the chemicals can damage your trans and valve body. A local honest trans guy here got rid of his machine and only does pan drops or what I'm going to suggest. If you ask him for a flush he will give you his card, suggest another shop, and and offer a free tow when it fails so he can do a rebuild.

First check your fluid level hot, make sure it is right.

Do a DIY flush with Mercon V(it is specific). That is a ford approved compatible fluid for your trans with synthetic properties and mandatory for 97+. That is all they use at the dealer BTW, for almost any auto trans made in the last 25 yrs. I'm wondering if your trans worked right at first but then the fluid mixed with the old stuff. This procedure would also prevent all the fluid spilling out of a full pan if you had to do another change.

Locate the top of your radiator, remove the plumbing like fitting attached to a steel line with two backup wrenches. Do not remove the fitting from the cooler, turn the small nut on the tube only, hold the large fitting stationary.

Slip a tube of appropriate size over the line. Let it run into a vessel (3L empty clean poland spring bottle is nice). A bit of fluid may dribble out the other fitting, you can plug with a rag.

Try to get an identical clean container.

Start the engine, allow 1.5-2 quarts (no more) to empty into the container. If the fluid ever stops (unlikely with this amount) stop the engine. Your pan is now nearly empty, and makes a pan drop easier.

Pour the identical amount of Mercon V back in the dipstick, fill the container to match the waste container.

You want to exchange about 6-10 quarts, I would try 6 at first and see if it is making a difference when you drive in your case. Normally you would exchange until your fluid turns red.

Check your fluid level hot.

Also, Band adjustments are service items that your dealer would check at 50K service intervals, just like brakes or oil changes. Old fluid may assist in their demise.

If the band adjustment and the fluid exchange fails, there could be a valve body issue or internal damage. A valve body can be tackled by a very experienced DIYer. Anything else requires dropping the trans.

 

[markcs]

Hi 96eb96,

Thanks for the additional advice. I rechecked the fluid when hot and it is at the correct level. One question, since I would not be changing the entire fluid in the system at once, is it still ok to mix Mercon with Mercon V? I am not sure when the oil change place performed the fluid and filter change the last time if they used Mercon or Mercon V? I did notice that they snapped off one of the bolts on the pan and quite a few of the bolts were loose.

If this does not work then I would probably will have to take the vehicle in to have the ban adjustment performed. This is not an procedure that I feel comfortable performing myself.

Thanks again for all your help.

Mark

Also, the issue also occurs with O/D off, while in third gear. Again once I reach 55MPH or faster.

 

[96eb96]

Hi 96eb96,

Thanks for the additional advice. I rechecked the fluid when hot and it is at the correct level. One question, since I would not be changing the entire fluid in the system at once, is it still ok to mix Mercon with Mercon V? I am not sure when the oil change place performed the fluid and filter change the last time if they used Mercon or Mercon V? I did notice that they snapped off one of the bolts on the pan and quite a few of the bolts were loose.

If this does not work then I would probably will have to take the vehicle in to have the ban adjustment performed. This is not an procedure that I feel comfortable performing myself.

Thanks again for all your help.

Mark

Also, the issue also occurs with O/D off, while in third gear. Again once I reach 55MPH or faster.

Sorry, I didn't read the the first post again.

Mercon and Mercon V are completely compatible according to Ford.
Here is the TSB:
http://www.modularfords.com/forums/showthread.php?t=94070

I was just thinking from a cost point of view cause the 12 quarts needed to do a complete change could be close to $50, and there is no assurance it will solve the problem. If you went to a dealer you would get V, since there is no more motorcraft Mercon. I have a mixture in my 96 and its fine, I gradually replace the fluid every few oil changes.

There is also an additive that I've used and is highly suggested by trans experts - Lube guard Red (get the red bottle, there are other colors).

http://www.lubegard.com/automotive/trans_atf.html

At this point, I would exchange a few quarts with V and add lubegard after. This will maximize the fricition properties of your fluid and unstick any valves.

The band adjustment may or may not help...so that is up to you if you want to do it (can't hurt). I think bands mostly affect 2nd gear and overdrive.

Now I'm thinking torque converter lockup issues, since it locks around 45-55 mph. Its all a guess, many places will just say rebuild the trans at 140K miles. You can shop around for an honest mechanic who will take the time to diagnose the problem (with scan tools and line pressure gauges), but then again at that mileage and the 70K fluid there could be other issues that will soon rear their ugly head....

I would call the trans places and ask specifically if they will seriously diagnose the problem and explain it to you rather than just suggest a rebuild.