Engine/Transmission (1994 - 1998) 47 RH: Whats Wrong?

[BGarofalo]

Not trying to beat a dead horse here but i have a problem with a new truck i just picked up. Its a 95 Dodge 2500 with an auto and 4:10 gears, 218,000 miles. The problem is i have no OD or lockup when driving normally. Its does not even try to go in, so I hit 61 mph at red line. But here is the kicker, when i go down a long grade with no throttle or very light throttle it kicked into OD but then quickly left. I swapped a known good TPS and no change, i tried the resistor trick in the temp sensor, no change, I tried to clean grounds and cleaned up the terminals on the ECM, no change. I also swapped a OD button, no change. What else am I missing? The guy I bought this truck from said it was rebuilt not too long ago but is out of warrenty on the rebuild.



Ive read about every forum i could find and tried most all of the solutions to see if i could fix this issue. I'm not an automatic guy so I thought i'd give it one last try before taking it to a shop. ANY INPUT PLEASE

 

[BigPapa]

I'd put money on the TPS or the brake pedal switch.



I put in a NEW TPS once that didn't fix the problem. I took it to the dealer and they hooked their little electronic thingy to it and said they had to "reset" it. After that it worked like a dream. So swapping the "known good TPS" may not be enough.



The brake pedal switch could be bad. I also had them mess up the OD function. It's a simple replacement, after you've done it a time or two. Just be careful with it because it is a self adjusting switch. The first time the plunger is pushed in it "self adjusts". So make sure you don't push it in while you're messing around with it.



Scott

 

[JPittinger]

Maybe check/clean the wiring and plugs on the transmission itself. I'm sure there is a way to monitor the signal to the solenoids at the plugs with a multimeter, I just don't know enough to tell you how. The 47RH's aren't as complicated as the RE's.

 

[Howard Durand]

The three wire cable between the PCM and the transmission provides voltage to the OD and TC solenoids through the center wire.

It also provides a ground return through the outside wires.

The 12 volt center wire is light green with a black tracer.

The TC solenoid ground wire is orange with black tracer and connects to pin 54 on the PCM.

The OD solenoid ground wire is brown and connects to pin 55.



If you have a voltmeter, with the ignition switch on, check the pins on the OD/TC control cable at the transmission. The center pin should have 12 volts on it. The other two are the ground wires back to the PCM from the solenoids. The PCM does the switching.



If you have an ohm meter you can check to see if the solenoids are good or not. With the cable unplugged, connect one probe of the ohm meter to the center pin of the transmission receptacle and the other to each of the two outside pins one at a time. They should each have about 30 ohms of resistance. This should prove that they are good.

Next connect the ohm meter between the center pin and ground. There should be no reading on the meter.

 

[BGarofalo]

I had already tried the brake switch and cleaning the plugs on the transmission. Of course no change. Ill try the ohm test tonight and see what happens.

 

[HughO]

Howard's post is dead on. Also, my lockups were intermittent and sloppy until I replaced the two solenoids and the differential sensor and now the shift to lockup is a reassuring solid clunk and mpg went from 16 to 20. 1994 2500 4X4 200K

 

[Joe G.]

Another thing you can do in addition to what Howards suggests is to rig a couple of 12 volt LEDs (get them at Radio Shack) to the three wire connector on the trans. Then mount the LEDs somewhere in the cab. That way you can see if the OD and lockup are being applied while you are driving. If they are being applied and OD and lockup are not happening then check the solenoids. If they are not being applied then look at the electrical stuff. TPS, PCM, wireing, etc.



Also try lifting your foot at speed and see if that affects what happens.

 

[BGarofalo]

Sorry for the delay Ive been busy. After trying the selonoids and other items and found them to be good I went back to the TPS. I put a resistor in line to knock the vollts down and reconnected it and it was successful. My OD and Lockup kick in at around 41 mph. So i will soon put a rheostat in line to make it a done deal. Its wierd that the other TPS worked in my friends truck but when I put it in mine it made no differance. Strange. Thanks so much for your help TDR has proved to be invaluable once again.

 

[Ridesamule]

Wire that Rheostat directly to the ECM and mount it in your dash. You will never regret it (MHO) especially if you use your truck to tow.



I ran the later years of my original stock 47re this way from 185-235K and never had an issue due to the rheostat.

 

[CLamb]

Kind of on subject



A friend of mine has a 95 that won't shift at WOT, any pointers? Shifts fine under normal driving but will never shift WOT

 

[Howard Durand]

Will it shift if he lifts his foot momentarily?

 

[BGarofalo]

Try adjusting the cable on the throttle linkage to give it some more slack. You simply have to squeeze the tab and slide the cable out. Or just unhook it for a test run.