I have a 1998 F150 4WD XLT Extended Cab with a 4.6l engine. I have 105k on the truck. I purchased it used with 70k and the tranny fluid was a bright red and didn't smell. I drained the torque convertor and pan and changed the filter around 95k. I tow a 6000lb R.V. with the overdrive off requarly and have had no trouble. I have the the tow package with the aux tranny cooler.

If I drive normally I notice no problems. What happens is when I lift the accelerator and then accelerate again I notice the tranny will jump to out of overdrive and then right back in to overdrive and the rpms climb about 500 more. If I am at lowers speeds I notice 2nd-third will do the same thing. 1st-2nd seem O.K. Is she going or is there something I can do or have done.

I have rebuilt a couple of chevy 350's before so I have a little background and I bumped into this web site (listed below) and they make it seem easy enough. But looks are decieving. I am not a know-it-all but I am pretty handy with a wrench. If a rebuild is necessary I will probably let the experts do it but if there is something I can replace to fix the issue like springs/valves etc then I will probably give it a whirl.

Help is apreciated. I like my truck. Thanks in advance.

http://www.mn12performance.com/mn12-...rans-tech.html

 

 

No overdrive when I tow. I am concerned enough now that I won't tow untill I have the issue taken care of.

 

You say you tow with overdrive off, yet say it jumps out of overdrive....

What's really happening is that the torque converter clutch will unlock when you lift the throttle. There is a delay to relock after you press the go pedal again, and that is when you see the jump in RPM before the torque converter clutch relocks.

It's normal. The only way to change it is to have someone write some custom software.

 

What casey says is technically correct. It happens to a greater or lesser degree in each truck. A tach and speedo combination is the only way you see this.
Few ever notice it.
The reason it works that way is when you have to slow in a sudden manner, the lock up has to disengage so the motor dosen't add to the braking effort in all gears where lockup is present. This is sensed by the PCM/EEC and controls the function with some timing action added in to be sure of what is happening. The TPS and VSS and brakes are also involved in the scheme of operation.
All the electric lock ups work the same way even in the 80s Rangers and Bronco IIs with the A4LDs.
In the AOD trans the lock up stays on above the min speed because there is no outside control until it drops out below about 40 mph +/-.
The 4R70 types that have no lock up at low speeds is one reason these trucks wear brakes faster besides being heavier.
Ever notice how much more these trucks seem to keep rolling without much power applied, and the braking needed on a more routine basis?

 

The explanations you give me help to understand overdrive operation beter. I guess I wasn't as clear as I needed to be. I explained I towed but that was to explain the amount of abuse I put on the beast. I tow with over drive off. I don't notice the in/out because over drive is off. I only notice it during normal driving when I don't tow. I also notice the same thing while towing or not towing with the 3rd shift. I let up she will drop out of third, I give her the gas and she will rev a bit (300-500 rpms) and shift back to third just like overdrive does during normal driving while not towing. It just recently started doing this. When in gear she holds steady with no shutter even with a heavy load like towing.

 

I hear what your saying now. You have a problem then. If there are no codes set or lamp flashing, a shop needs to be consulted.
Good luck.

 

Go have it checked out. If you find an honest shop they will tell you that they can't find anything wrong because it is working as designed.

 

Thanks Guys for your input. The overdrive in/out I understand now. The third gear in/out makes me concerned since both just became noticable. I just hope something like an acumulator spring or something in the valve body or some part that is changeable without droping this beast is the culpret. I know I am probably dreaming. I know how my luck is. Casey I see where you are coming from but the problem just started recently. I don't want to get stuck 250 miles from home with 6000lbs behind me and parts all over the blacktop. Finding a shop that will be honest may be a concern. This situation makes me more frustrated than a pervert with palsey trying to draw ***** with an etcha-sketch; Or so Larry the cable guy said.
Again thanks for you input it is apreciated.