I recently purchased a 2000 Dodge Ram 1500 Laramie from a private party. It test drove fine and it was from OK. so no rust and we bought it. NOW, I drove it 140 miles to get a trailer and all worked just fine. Coming home we had no overdrive. Changed fluid and filter. No bad smell and very few shavings. Took it to the dealer(not normal) and they wanted to tear it apart. NO. Pulled a trailer 30 from home OD works fine. Coming home no OD. Tranny shop said it runs and shifts too good to be major and indicated it was not getting signal to upshift into OD. I have changed the output speed sensor and plug along with the tranny control plug on top as they had bare wires. Still no OD. It has a 5.2 with I believe a 46rh-re Trans. 185000 miles Runs and shifts good. OH YES, it does not pull a tranny code either. Where do I go from here?

THANKS

 

it's a 46RE.

Its either the PCM not commanding O/D, O/D solenoid, Transmission temp sensor giving false reading, or the O/D piston seals are going bad. When my O/D piston seals where going bad id have O/D sometimes and others not.

I would start with the easiest, test the PCM to see if its commanding O/D. To do this probe B21 (white plug) with a muti-meter. You should have 12+ volts while its in gear 1-3 and when the O/D off button is pressed.. once it commands 4th (O/D) the volts should drop to 0. If it does that then your PCM is good.

You can also test the transmission temp sensor by probing pin 1 of the same white connector. This one you wanna measure the ohms and a 70F you should see close to 1000 ohms

 

Don't pull a trailer in O/D either.

Welcome to DF!

 

Old school: I will start with the measurements. The tranny guy did say the red wire on the tranny control plug should have 12v and it does not.
Good place to start.

Hey You: Trailer was very light. & My fifth wheel doesn't see overdrive.

Thanks guys,
Time for some work in the morning.

 

I *think* the trans control relay operates the same way as the ASD relay, in that: if the engine isn't running, you will only see power for about 3 seconds.... then the PCM will turn it off..... until it sees the engine turning.

 

That's what mine did when i tested it.

 

Thanks. Got waylaid yesterday so today is the day to get started.

 

Okay, I have 15.5 volts in 1-3.
I have 15.5 with button out when it should be in OD
I have at 73*F 1280ohms
Another post suggested to ground out pin 30 to pull in the relay but no go.
Any more suggestions?
Thanks Bill

 

I have also jumped the relay to give it signal. No luck

 

Relay only supplies power. According to theory, PCM won't request O/D until trans is up to 108*, or so.....

Does the sensor think the fluid gets warmer if you drive it for a while?