Automatic Transmission will not Downshift
 

I have a 1998 Ranger 4WD 4.0L 5 spd. automatic 110,000 miles --the transmission has started not downshifting properly -- noticed it when starting to go uphill in mountains -- intermittently (at least 75% of the time) if below 2400 RPM and under load it does not downshift -- it attempts to downshift and there is sort of a clunk/lurch/hesitation but does not complete the downshift -- can be downshifted manually or by briefly letting up on the accelerator and then depressing it -- will also downshift under load by taking it out of overdrive (if OD is already off it behaves the same way as with OD on) -- fluid appears a normal color to me and the OD light has never flashed -- have taken it to a Ford dealer and they cannot find the problem -- does not show up with their computer diagnostics -- would certainly appreciate any ideas on how to fix this short of replacing the transmission

A few things to check for loose, broken wires or inop components:
1. Transmission Range Sensor
2. Transmission Control
3. Vehicle Speed Sensor
4. Kickdown cable adjustment
My first thought is the kickdown cable. It is located between the transmission on a ball stud, and on the accelerator cable. Have you installed carpets or pads that could be interfering with the throttle? Maybe the cable itself is broken or sticking. Good luck, and don't replace the transmission yet. When was the last time the fluid and filter (all the fluid) was replaced? If it's been a while, a good investment for your truck is to change them. Keep us posted.

I appreciate the support and comments -- have been out underneath my truck and do not think I have a kickdown cable -- think it may have been replaced by a PCM command (transmission is 5R55E) -- I now have a Ford Workshop Manual and am trying to figure out how this thing works -- I believe the function not working is called "Torque demand downshift" -- appears to me the PCM must command a gear change and a torque converter command (and probably more) -- notice there is a "4-3 downshift valve" that is controlled by one of the solenoids -- wonder if this guy could be the culprit??? -- wondering if a flush job might fix this ???-- would it be a good idea to add one of the "fix-it" solutions prior to changing the fluid -- if so what is the best one to use ??