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Transmissions issues.

2007 Views 24 Replies 4 Participants Last post by  DarrenGregory
Hey guys I have a "new to me" 95 3500 dually automatic 12v w/ 90hp injectors and an airdog fuel system, the guy before me had gotten it from a kid that put a lockup switch on it, when driven you gotta flip a toggle switch after you hit 30mph to lock the torque converter in, then it shifts to third and then overdrive, it also has a light dimmer switch to adjust when it shifts into overdrive, what's the easiest way to remove the lock up switch and make it back to stock?, also my tranny temp light comes on and off when I flip the switch and when I'm runnin slower than 60 in o/d, is it possible that it's actually hot or is the switch messing with the trucks sensors? The tranny cooler has some bent fins if I put a new tranny cooler on could that possibly solve the problem?

This is my first cummins, I also have a Duramax

Thanks for the help!

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If you want to put it back to stock then you probably won't have od lockup anymore. That toggle switch is there because it quit going into lockup and that's way cheaper and easier than fixing the real issue. :hehe:
Is that actually a common issue with the transmission on these dodges? I heard that but then I've also been told that the lockup switch is just to put the tranny in o/d faster to blow a lotta smoke?

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It's an issue. Most of the time the switch is to control the tc lock off and on. In your case though it sounds like its controlling the tcc off and on. Will your truck shift into od without the switch on?
The gear line up is 1-2-flip switch-3- o/d, the switch has to be on to go into 3rd and overdrive, and if I leave the switch on when coming to a stop it will shake like a just like leaving a manual tranny in gear and hitting the brake at a stop light until it stalls out

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You've definitely got an electrical issue that won't lock in the tc. Without that switch you won't have lockup. I'd say keep it unless you really want to do without it then start looking at your TPS. That's usually where the problems start.
What's tpc? And if I got my tranny rebuilt would that eliminate pretty much all my issues?

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The truck has 283000 miles on it idk if it's the original tranny or rebuilt but it still works with the exception of the switch

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Throttle position sensor. Make sure it's reading properly. Follow these steps

TPS testing and adjustment

If that all checks out then I'd replace the pressure sensor and transducer inside the pan. The pressure sensor has a fluid temp sensor that can prevent upshifts or downshifts if it sees the fluid is to hot or cold.
I'll take a look into it and see what if it works, will this eliminate my switch Or fix the temp light issues?
Should fix both.
Alright I replaced the tranny cooler to see if it that was the reason for the temp light coming on, apparently it has 2 tranny cooler a skinny one on the driver side next to the ac cooler, and then it has one mounted on the ac cooler, the fluid flows out of the tranny into 1 cooler then through a line into a second cooler, then back into the tranny, I replaced the one mounted to the ac cooler and just completely removed the ac cooler due to the ac not working anyway, so I mounted the new tranny cooler to the turbo intercooler, all the lines are hooked up and goin good no leaks or anything, I am going to add tranny fluid ATF +4 then see if the temp light comes on, if it does, could it be one of the sensors in the pan shorting out or just quit working? And if so would that cause the light to come on and off when I push the gas and let off? And if it's a sensor is it critical to replace it or can I just drive it with an "idiot" light on so to speak?, I really don't have to money to do a whole lot so I need the cheapest solution possible! Thanks

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Alright I took it for a test run and she drove smooth at 58mph+ but if I drive at 55 it comes on, the only way I can describe this like in a normal automatic and say you're traveling at a set speed and you go up a slight grade and you're tranny downshifts to handle going up the hill, well when I'm driving at 55 it seems like it can't haul it's own and needs to downshift but I'm driving on flat land, and my tranny can't downshift due to the lock up switch and that's when my light comes on at 55 or so, this thing is soo confusing but I feel like I'm making a little bit of progress, I'm starting to consider on selling this truck or trading it for something I can understand especially when I don't know anything about mechanical diesels!

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You definitely making a progress by considering selling the thing :hehe:
Seriously, your mechanical diesel has no issues, its your computer controlled automatic transmission has a problem. It will be cheaper to find local guru to fix it before you sell it vs. sell it as a "mechanics special".
The pressure sender in the pan has a temp sensor in it. If it doesn't know what kind of line pressure it has in the trans, it can't regulate that pressure so it might slip or go into limp mode. (Second gear starts) this is probably the source of your problem or part of it at least.
I have first gear though, it's really short but I do have first gear…

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Alright so I've been looking and researching does my 95 have a pressure solenoid and pressure sensor in the tranny pan on the outside of the valve body? I'm not sure what tranny I have 47re? Or 47rh? What's the difference? And on eBay I only find the pressure solenoid and sensor for 96 and newer with the 47re tranny nothing bout a 95 so I'm question that I have one, but what #cummins said that sensor could be the problem, it "thinks" the fluid is "hot" and is putting the truck in a stage of limp mode where I won't have overdrive but I'll have 1st 2nd and 3rd, this make sense to you guys? I can be driving and the tranny temp light will be on and it won't go to over drive but soon as the light goes off it will shift to od, so od does work, it's gotta be a sensor issue right? The physical gears in the tranny feel Sturdy I mean if I can be on a dry road and build my boost to 20 and smoke my dually tires and have no tranny light and no slippage I'd say it's a dang electrical issue, what y'all think

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1994-1995 47RH
1996-2002 47RE

You have a 1995 with a 47RH.

The biggest difference between the 2 transmissions is the governor. The 46RE is more electronically controlled. The 47RH is a different length compared to a 47RE.

The transmission temp sensor should in in the metal transmission line itself. There is a bung the sensor sits in. You can replace it with a 1,000 ohm resistor from radio shack for around $1 to rule it out.

Resistor needs to be 1k ohm (1000 ohm)
A bad brake light switch will also cause no lockup.
Switch has three sets of contacts, brake lights can work fine but no lockup.
Sometimes you can overcome a bad switch by lifting the brake pedal with your foot while at lockup time. New switch is $11 at Napa.
also check TPS testing and adjustment
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