Odd 48RE transmission shift

[Philc56]

Hi All, I am new to this forum and appreciate the help,


Coming back from the cool north to Florida my 05 Dodge diesel started running a bit warm. It was not overheating just a little hotter than normal. My temp. gauge usually sits just in the center line or even a bit to the left. I usually do my towing in the cooler months so running in 95 degree weather may have something to do with it. I checked all the obvious things radiator and hoses. I always run in Tow/Haul mode when pulling. I kept an eye on the gauge and it rose to just above the normal center line.

Coming off the interstate for a fuel stop the truck down shifted out of O/D way before it should. I mean at like 60 mph. I thought that odd and after fueling and back on the road the truck repeated the odd downshift several times when going down very shallow slopes. So I thought maybe it was the 48RE transmission.
I took the truck out of Tow/Haul and the temp went down close to normal in the 95 degree weather. The shifting was normal and the truck ran fine. On the last day from Georgia to Fl. I ran in Tow/Haul and everything was fine.

Since being back in Fl. and not towing the truck runs fine. My guess is there is something in the Tow/Haul that was causing the odd shifting and warming of the engine temp. If anyone has had this happen or any ideas I would be interested in knowing what was the cause and the cure.

On the RV.NET site a couple of people said it could be my fan clutch. I don't think it is this because the RPM jump up when the truck did the odd shift.

One more thing, there is a flash for my transmission that some have said should be done. It allows the lock out of O/D when in T/H and you take it out of T/H when running at high way speed. It seems to me that would cancel out what the T/H is made to do. The longer shift points and that would put more stress on the transmission.

Thanks,
Phil

 

[cerberusiam]

In 95-100 degree weather towing mine always runs a little over 200, the rest of the time a little under 200 degrees. There is nothng in the TH that will casue the engine temp to go up, on the contrary it should lower it because the lockup algorithm is more aggressive.

It is possible it is the fan clutch going bad and throwing weird signals back into the ECU. When that happens th eengine may shutoff or the windshield wipers ranomly activate or blinkers come on for no reason. Check the codes and see if there is anything stored as first step.

It is also possible you have a trans tmep sender that is on its way out feeding invalid to the ECU. A more aggressive and frequent downshift to drive is the ECU's reaction to what it sees as excessive trans temps. It could also be a problem in the trans harness on the VB going bad and causing the the transducer to read wrong.

Unless you are going 45-55 mph there is no reason to lockout OD. As long as you can keep the rpms in the 1900-2100 range towing that is where these engines like to run. The flash makes the TH button an OD lockout only but you loose the good parts of the TH. It is a hack not a real solution.

You did not indicate what your GCVW was so it is hard to tell if the problem is with the truck or the load.

 

[Philc56]

cerberusiam

I checked the codes and the three key engine code said DONE and the one key trip showed 00 00 I am not a mechanic and don't know the lingo. (ECU-VB) Any other suggestions?The truck 3500 dually and my 5er is about 14k I am thinking I will take it to a transmission shop or should I be looking at the fan clutch.

It sounds like you are not a fan of the flash to lock out the O/D, Any other ideas on that.

Thanks,
Phil

 

[cerberusiam]

No code sis good, means thta nothing is showing as wrong. The ECU is the power train computer, it runs the engine and all the transmission function and a lot of the body stuff also. When it gets a glitch for whatever reason weird things can happen.

The VB is the valve body, that is the brain of the transmission. A very limited and reactive brain not a smart one. It basically does what you tell it with the shift lever and how to perform by what the ECU tells it via a few electronic parts that influence its operation. The TH button is one that influences how it shifts and lockups up. The governor pressure and tmep system is a feed back system that influences how the trans will function. ANY problems in those circuits will impact what you feel form the trans. If the temp sensor reads high it will try to downshift to drive at the first chnace attempt to rectify a hot reading on the fluid even though it may not be really hot. Just on example of flase readings impacting performance.

Intermittent stuff is always abugger to track. However, the control harness on the VB and the connector where it comes thru the trans case are the root of a lot of problems. If the thru case connector gets a small crack it will leak trans fluid into the connections and randmly send flase data to the ECU, make the temp light come on, refuse to go into ans stay in OD, make the TC lcokup function totally unreliable.

Not a fan of the TH flash at all. The TH function on an 05 is huge plus especially whne towing heavy, the lack of an OD lcokout is the big negative. That can solved several ways, ATS and BD Power make and add on controller that allows the OD lockout function when needed and still retain the aggressive lockup and shift features. A simple manual switch can do the same thing. There are better solutions that a step backwards in trans control.

 

[Philc56]

cerberusiam,

What would you suggest from here? The transmission shop or engine place for the fan clutch? Is the control harness something I could do? Is it plug and play? Any idea of the repair cost for this situation? What did you mean by "There are better solutions that a step backwards in trans control."

I appreciate your help. I will be pulling the RV from Florida to Wyoming next spring and I want everything right.

Thanks,
Phil

 

[Philc56]

sorry about the double post

 

[cerberusiam]

How many miles on the truck? When was the last transmission service?

The harness is really plug and play but it reguires partial disassembly of the trans while still in the truck. You have to drop the VB to change the harness.

The solutions that I feel are better are an OD lockout controller form BD Power or ATS, and a simple lockut switch. Both require cutting and splicing wires in the harness.

 

[Philc56]

The truck has 137K all stock. I got it with 87K I full time RV. I have towed all over the U.S. east to west North to south with alot of time in Wy, Ut, and Az. mountains. I believe I have done about 10-12K towing mainly the interstates the rest just daily driving. I had the transmission serviced about 5-6K ago at a Dodge dealer in Cottonwood Az. They tightened 1 band and said everything else looked good. There is no leakage underneath that I can tell other than minor road crime and a bit of grease.

 

[Philc56]

cerberrusiam

One more thing that may or may not have something to do with this. I had forgotten until now. My A/C was not blowing cold. I stopped and charged it. It fixed the A/C. I think I was running out of T/H after that for a day about 3-400 miles. Like I said above the last day in T/H and everything was good except a minor raise in engine temp in 95 degrees.

 

[cerberusiam]

Maybe hit a bug swarm and partially plugged the radiator? Possibly the thermostat is sticking? I have had both problems intermit then get worse.

 

[Philc56]

Took the truck to the transmission shop today. There were no codes and everything looked ok. The said it shifted fine. The fan clutch is working too. They said if the A/C was not cooling right that could cause signals to the ECU that could cause my issues. I had to charge the A/C when all this occurred. I don't remember if that was before the last day when things seemed to operate OK. I am going to keep an eye on things and see what happens.

Thanks for the help

 

[cerberusiam]

Make sure the rad is clean and drive it. Intermittent problems are a pain to find an absolute source.