I think the pressure switch and/or transducer in my W250's 46RH is acting up. Does anyone have the mopar part number for these parts? I'd like to call the dealer to order them but want to ensure we get the correct parts.

Thanks for looking!

Od is electronic control on those. Ecm uses tps and vss readings for control.

Speedo work OK? Engine run OK?

It is a 5.9L CTD. It runs and drives excellent. I was under the impression it did not have an ECM.

It still has a computer to control OD. Also the computer controls charging, cruise and some other bits.

Tps problems are common.

93 with a 46 RH??? Should be a A518....basically a 727 with OD. The TPS is a common failure, and also the speed sensor on the transfer case. A little drive with a scanner should show if there's any gap-outs in either. Speed sensor is fairly cheap, but the TPS will set you back some coin!!

I am going to go along with that and agree that it must be a 518. I'll order both parts and swap them out.

Would it be a good idea to do the TCC/OD control solenoid as well?

A518 only has the OD solenoid on the valve body. There is no lock-up convertor. Personally I have only ever replaced 1 solenoid....they rarely give problems unlike the Governor ones in the RE transmissions . Has your speedo by chance been quitting intermittently??

The speedometer has been rock solid. Here are a few scenarios that describe what is happening:

1) Coming down a hill at 75mph and let off the gas abruptly (someone cuts you off) and it will shift out of OD.

2) Sometimes you have to let off of the gas to get it to shift into OD. The shift seems fine; it seems to be more of a user input problem. The TPS seems like it might be related to something like this.

Thank you for the insight on my issue. I love this truck and use it often so getting our problem resolved is a high priority.

Thank you John, I'll follow the TSB and report back.

It's the TPS, always is. If you want a genuine Cummins part the cheapest I've found is at Geno's Garage. About $190.

When new, my 92 ctd had the same problem. Random shifting, then no overdrive at all.

Went through numerous tps sensors, the problem always kept coming back. It got so bad I would just pull up the the mechanic's bay & pop the hood. We would go to the counter, by the time the paperwork was done, he had the truck fixed.

The last fix was tps sensor, speed sensor and the dealer put a short speedometer cable (10" long) between the speed sensor & transmission to isolate it from vibration.

Never had a problem since.

Ed

Thank you for the suggestions. I ordered a TPS, speed sensor and OD solenoid. We will see what remedies my ailment in a few days.

The speed sensor is basically only for the speedometer and cruise control. If the crank sensor is bad your a/c won't work either. The solenoids rarely if ever go bad. The TPS on the other hand is for the O/D only.

I had made a bracket to use a regular gas engine TPS off a Caravan 3.0L V6. It worked ok, not quite right though. It ate those sensors about every 6-8 months so I just bit the bullet and bought the correct Cummins unit.

Do yourself a favor and save some money, put the TPS on first then after it's fixed you can send the other parts back.

Ecm needs vss readings for control of OD.

No vss=no OD

Diagnosing a problem is mostly a matter of elimination, comparing what other systems use the same inputs and are working correctly can eliminate that component or sensor.

VSS is used by the speedometer and cruise control. If the VSS was bad the speedometer would be inop or erratic as well. The PCM only needs to know that the vehicle travelling at least 32 MPH for it to allow O/D. It could be reading 40 to 60 MPH regardless of actual speed and the O/D would still work.

Thus, everything else working fine leaves only the TPS.

That's not what you said before.

Which time? The one where I said it's always the TPS or that the VSS is basically for the speedometer and cruise control?

I probably should have said that by the description of the condition and information provided by the OP that it's always the TPS but I hate typing on this tablet so answers can be short and concise, sorry.

As for the second statement I stand by that. The PCM does not constantly monitor the VSS signal for O/D. It only cares that it's above 32 MPH to allow it and it turns it off at 30. The speedometer and the cruise control are very reliant on the VSS though and it's exact reading at all times.

The PCM also needs to know that the coolant temperature is above 60 degrees but it doesn't constantly monitor that either and no one mentioned that or the transmission temperature switch. All of the OP's described conditions involved throttle input, so I refer back to my first explanation. I hope this helps clear things up.

And BTW, '93 was around the year when the designations changed so the OP's original description of a 46RH is indeed correct.

Since I am clarifying things and I can't sleep I'll also say that the 518/46RH in the diesel application was non lockup. There were gas versions in both lockup and non lockup. The lockup for the diesel didn't happen until 94 with the 47RH. The VSS was additionally used in these applications for lockup control independent of O/D.

It is also possible to convert the non lockup 518 to a lockup. I did it to my 92 and it totally changed the characteristics of the truck. Less RPM, less heat, quieter cabin, better fuel mileage and excellent highway passing power. It's the best modification that I've made to this truck. The only thing I need to work out is an independent control of the lockup. I just tied it to the O/D so they work together but with a switch so I can turn off the lockup if needed.

My point was that the vss isn't just for the speedo and cruise. OD does need a reading from it. An erratic reading can ause the od to drop out of engagement. Which is why I also asked if the speedo and cruise worked correctly.

I asked about engine running since the op didn't specify a diesel, gassers with a flaky tps will run oddly.

I agree with the rest of your information, and yes even the 518 can be converted to lockup. But that's a compete rebuild option, not a minor repair.

And one last input, besides the cold eninge switch, there is a trans temp switch that will kick the od off if the temp gets too high. IIRC the switch kicks off at like 250 (way hot)

Still, as with you I bet the tps is funny, a sweep test will confirm it.