lumpy_63

I have a question for someone that is electrically knowledgeable. It seems that when people have problems with their 47re transmissions "hunting for gears", there are different solutions that work for different trucks. The solutions often involve noise filters. Some people talk about using capacitors, and one person (lwowen) used an inductor (RF choke). I was reading in my old physics book that capacitance dominates at low frequency, while inductance dominates at high frequency. If the problem is noise from the APPS/TPS, wouldn't it be a low frequency problem, and therefore need a capacitor as a filter? If the problem is noise from the alternator, wouldn't that be a higher frequency problem, and therefore need an inductive filter? If that is the case, is there a way to use both capacitance and inductance to filter the noise, to be most effective? I am not very electrically inclined at all, but the posts I was reading just made me wonder about this.

I asked this question at the end of a different thread, but it seemed like it would be a different discussion... Sorry for the length of the post.

SMOKNISB

Most of the problems I have heard of consist of the convertor locking and unlocking. This can be solved simply by shielding the wires to the tranny. There are harnesses on the market to fix this. Some have even gotten by wrapping the exsisting wires in aluminum foil.

lumpy_63

Thanks SMOKNISB. So far I have:

* Taken it to a reputable transmission shop, who couldn't find any codes but replaced the APPS, which had no effect (still hunted for gears)
* Took it to another reputable shop who removed 1.5 quarts of fluid, which had no effect. They could not find any codes and said (after removing fluid had no effect) that they believed it was an electrical problem. Their "hotline" said the next thing to do was have the dealer re-flash the computer. I am leery of dealers and of re-flashing the computer, but I have an appointment this coming Friday to get it done
* Sanded to bare metal under the grounds (from the batteries and the PCM) and cleaned up the battery posts / terminals
* Ran a new ground wire from the PCM to the ground that the neg. cable from the passenger battery connects to (some say to ground this wire to the negative battery terminal itself, I think).
* Replaced the transmission relay
* Wrapped the black wire with tan stripe that runs over the alternator in aluminum duct tape, winding in a ground wire and grounding it to the ground on the body by the passenger battery. I also zip tied the wire as far away from the alternator as I could.

Result? I still have the problem. That is what led me to ask the electrical question that I did. I am now investigating the alternator ground (supposedly it connects to the block by the thermostat, but I don't see it on my '02) capacitors / DTT noise filters / inductors / / wiring harnesses / ??? / trading the truck in. I would appreciate any further input.

SMOKNISB

Is the tranny hunting for gears, or is it just the torque convertor locking and unlocking while driving a constant speed.

lumpy_63

I am pretty sure it is hunting for gears. The rpm will go up once, then go up again, when on the highway (then it just hunts around). It has also happened at speeds as low as 20 - 30 mph so it doesn't seem to be exclusively a 4th gear lockup / unlock issue.

lumpy_63

After trying almost everything else (see earlier post in this thread) to stop my 47re from "hunting for gears", I bought a snap on rf choke from Radio Shack a week ago. The tranny was hunting for gears most days. I snapped on the choke around the ground wire (black with tan tracer) that runs over the alternator, near the battery. I thought what the heck, I will put it there for now and move it next to the APPS when I get home. Well, guess what. It didn't have a problem as I traveled home, so I left it there. It has now been a week and the tranny has not hunted for gears once. Is it possible that the alternator puts out so much noise that it "contaminates" the other ground wires? I am not very electrically inclined so I may be way off base. By the way I got the idea to try an rf choke from lwowen, who posted about it fixing the same problem for him back in 2004 (although he put it around the APPS wire going to the PCM as I recall). I am getting some chokes with a smaller ID to put around the APPS wire going to the PCM too. The chokes are ferrite cylinders that are cut in half; you just "clamshell" them around the wire you are interested in filtering. I guess they are used to reduce noise in computer cables. I had thought about changing the alternator brushes but I have the Bosch alternator and I haven't located brushes yet (haven't tried that hard to be honest, since the choke worked).

triumph74tr6

I went to radio shack tonight and bought the snap on RF choke. I installed it and drove home to test. It made my hunting problem much WORSE! I took it off, and the transmission went back to its normal hunting.

daddy mopar

while trying to hold a speed at about 30 mph +/-, OD disengaged, mine will hunt non stop.

It does the same at 45+/-.

It just jogs back and forth between gears.

Does this sound lie what your trans was doing.

What would you recommend from your experience I do first?


PS my trans is 2 months old, new converter, tranny - dodge reman.

olddodgetrucks

did the ats rewire,no more hunting,1 year ago.

dozer12216

There is "NO one cure fixes all" for this issue.
To see if alt is causing problem disconnect the two wire connector or the small wires attached with small bolts. This will disable the alternator and allow testing for alternator noise as cause. A fault code will be generated but go away when hooked back up. I used a old ignition condenser from alt + terminal to case to cure mine. I also shielded the small wires to alternator by wraping with small wire for 12 inches and grounding the shield. Have you cleaned all the heavy power conncetors including one behind starter?
A bad brake switch, a bad RPM sensor on side of OD housing, a APPS signal are some additional problems.
This issue can be resolved if you get personal enough with it. There was also a bulletin for upgraded solenoids in tranny. The only ones I trust are from dealership. Don't know quality of aftermarket source.
There are several supposed trans fixes by tranny rebuilders. Sometimes they work and some don't.

glenn-k

I tried several things with mine. Finally installed a mystery switch and just lock the TC when it acts up.

Jeff5886

What he said

oudive

Try this as it will only cost you some wire, a couple of connectors and a little time. Click here and check it out. I did this and have not had the problem return so far for the last 4,000 miles

jrs_dodge_diesel

Understand that the overdrive lockup clutch is controlled electrically by the PCM.

The effect that is occuring is known as a "ground loop". Ground loop cause unwanted electrical "noise" on electrical and signal lines. The lockup clutch is controlled electrically and a noisy control line will make it "hunt". An alternator putting out dirty power can cause the same effect but that is not very common.

http://en.wikipedia.org/wiki/Ground_loop_(electricity)

Dirty connections, corrosion, and loose connections all contribute to ground loop. Fixing it is easy though. Generally involves cleaning ALL ground connections affecting the transmission and controlling it. Batteries, frame connections and the PCM on the firewall all need to be cleaned.

IMO tin foil shielding and power filters are simply band-aids that mask the underlying problem if left unchecked. And like I said before a simple cleaning with a wire brush and a piece of sandpaper will normally fix the problem with the lockup clutch.

Here is one of my posts from another thread involving the same issue.

I had the lockup issue and it immediatly was solved after cleaning the grounds. Best of all, this fix is free!

Kybel

Installed a DTT Noise Filter on mine for the lock / unlock problem with the tc and have never had a problem since. Simple install also.