joebishop23

Hello everybody,
my truck has started down shifting in over drive. at 60 mph cruising it will just softly down shift and then shift right back up. the rpms will go from about 1600 to 1800 and then back to 1600. it might do this 10 times and then it might do it twice. never can tell when it will do it. then sometimes i will get mad and punch it it will accelerate normal in over drive and then drop a little harder like i described before. i have put some additive in it like one shop told me to, it fixed it for a month or two and now its back and getting more frequent. i have 90,000 miles on it, i am getting ready to change the fluid at 100,000. anything i might try? thanks for the help.
Joe

Wolfeman

This is an electrical noise problem. Many posts on this, search on TC locking and unlocking. Easy first step, clean the battery terminals.

joebishop23

How can i tell what kind of auto tranny i have? EX: 47re, 48re.

RLee2500

You have a 47re, the 48re did not come about until the 3rd gen trucks. Clean your battery terminals, and wrap the brown wire that comes from the alternator with aluminum foil. I was having a few small issues with my tranny, and did this and it has been fine ever since. Do a search as already mentioned, and you will find a lot of info about the 47re and noise interferance issues.

patdaly

And if that doesn't fix it ( always do cheap first! ) change your TPS. Thats what it took to get mine squared away.

bama

before i changed my tps,,,,i would contact dtt about a noise filter..ive seen these fix these problems repeatedly.ive personally never had the foil trick help at all...........bama

glenn-k

Reset the APPS also -- it causes searching for the right gear - mine was doing it around 40 mph though.

https://www.dieseltruckresource.com/...n&onlynewfaq=1

joebishop23

Ok so i wrapped the alternator wire with aluminum tape. and did the apps reset ( unplugged the battery cable and push the gas pedal, etc.). it seems to be working alot better and i did se an improvement in throttle response. my question is do i need to do the apps recalibrate where you adjust the voltage? and the other fix that calls for a jumper wire to the ground of your battery and another one from the apps to the pcm? or should i leave it like it is since it is working alot better? i only drove it about 50 miles since i did it and i will know more about it once i hook a trailer to it this afternoon, it seemed to do it worse with a load on it. this site is amazing i cant believe how much good information i have gotten from all of you. thanks for all the help and the money i have saved!
Joe

glenn-k

If it's working I wouldn't fix it.

It could do it again - mine did in about 6 months -- cleaned all cables and grounds - reset the APPS again -- it is fine again.

Bushface

added that dtt noise filter and works like a charm, took me 20 min to install. My truck the tranny was locking and unlocking at about 48 mph and driving me crazy. Seams to work better at all speeds.

AlpineRAM

Sometimes the electrical noise part is a bear to find- if you get this more often with a trailer it can well be the higher electrical demand from the trailer- this would point to the alternator brushes or the PCM ground.
PCM ground is easy to do yourself- just make a wire to connect the PCM case to the negative post of your passenger side battery.

Alternator brushes can be had at www.fostertruck.com . If they are worn you get a lot of issues, but the first sign is the TC lock-unlock in a lot of cases.

HTH

AlpineRAM