Engine/Transmission (1994 - 1998) transmission shifting problems

[snake]

95 truck having automatic transmission problems coming out of overdrive, going over 50 mph. If I pull off the road and stop for a minute then take off again, it solves the problem for a while.

Things I have tried to correct the problem are:

Cleaning up the throttle position sensor, that didn't work.

Took it to a transmission shop and they changed the fluid, filter, and switch inside

the transmission That didn't work.

The problem doesn't happen every day, sometimes it goes for a week, sometimes it goes for a day or too.



Thanks,

David

 

[Joe G.]

You might try to adjust the TV cable and see if that affects anything. Mine has done that since it was new. I don't stop. I just punch the OD lockout button and keep going. Mine might do it once a year or it might to it within the next mile. Mine usually does it when I have the cruise on. My exhaust brake in on all the time with the TCC locked, so when the OD and cruise drops out and the brake closes it really attracts my attention. I don't think it has anything to do with the transmission hardware. Problem something in the PCM.

 

[GHansen]

Had the same problem and tried all the fixes. Finally pulled the connector at the OEM temp sensor, cleaned it with contact cleaner, scuffed up the contacts a bit and stuffed the cavity with dielectric silicone compound... worked in my case - lasts as long as 6 mo before I have to do it again (usually after a drive in the rain - weird ???)

 

[Joe G.]

Now that you mention it, I don't think my "ghost" downshift has happened since I replaced my temp sensor with a 700 ohm resister. I use the port in the cooler line for my trans temp gauge sensor now. Who knows? Maybe that is fixed now.

 

[snake]

I Cleaned Up The Oem Temp Sensor, And The Other Two Sensor. It Ran Good For A Day Same Problem Again, A Day Later ??

 

[Joe G.]

Pull the temp sensor connector off the sensor in the cooler line. Put a resister between the two pins in the connector. See if the problem goes away for good.

 

[Reb.B]

I have a hunch that this is not an electronic problem. The way to find out is put a simple grounded switch to the wire that goes to the overdrive. If you flip the switch on and still no O/D, then its clutches or the lip seal. If the oil was burnt when you changed the fluid before and they was friction material, then its probably clutches, in either case put between 1 to 2 pints of brake fluid in the atf and get the transmission warm. If this solves the problem then it was a lip seal and you just bought yourself about 20-40k miles. The brake fluid soften your lip seals, this lets them seal again.

 

[snake]

automatic transmission problems

I cleaned up the throttle position sensor, do you thing the sensor could be bad? A new one about $150. 00?

 

[Reb.B]

I haven't found one under $220. If there are some cheaper ones aftermarket i would sure love to know about it.

 

[snake]

WELL YOU HAVE IT RIGHT I CLEANED UP THE OEM TEMP SENSOR, IT RAN GOOD FOR SIX DAYS, UNTIL IT RAIN THAT DAY. SAME PROBLEM AGAIN FICKING OUT OF OVER DRIVE. I WILL TRY THE dielectric silicone compound. ?

 

[snake]

Well the problem is back, it ran good for nine day after I used dielectric silicone compound on the OEM and the Other Two Sensor on the transmission. In the cab I cleaned up the OD switch.

 

[Joe G.]

Snake,



Try this. Remove the connector to the temp sensor. Put a 1K resister in the connector. Put some silicone around the resister to water proof it. See if the problem goes away for good. If it does then use the port in the cooler line for a trans temp gauge.

 

[snake]

Well, Joe that worked Put a K1 resister in the connector. I also put a toggle switch in the

toque converter clutch and overdrive solenoid electrical connector {brown wire}. Transmissions

shop said I need a powertrain control module {PCM} about $500. 00. see if that works. I called DTT in Washington State said I sould used a K7 resister? I'll see if that works. What a dam nightmare. All it is a DAM GROUND problem right?

 

[Joe G.]

Snake,



The resister tells the PCM that the transmission is warm enough for OD. That's all it does. Any resister value that does that will work so changing resister values will have no affect. The resister either works or does not work. Period. The temp sensor is a resister that changes value in response to temp.



I think the PCM that is used with the 47RH transmission has some sort of programming error. Changing it might or might not affect the problem. Probably not. The switch is overkill I think.



You should get some experience running it with just a resister in place of the temp sensor and see if that takes care of the problem without doing anything else. If the problem still comes and goes then you may have to have the PCM reflashed. You may need some patience to solve this if the resister does not do it. If there are no other odd things going on it is probably not a ground problem.



Transmission shops don't understand this problem because it only affects '94 and '95 Dodge Rams with the 47RH transmission. It might affect the 42RH and 46RH transmissions which were used in the gasser versions of those trucks, but I don't know that for sure. These transmissions are the last ones to have a mechanical governor in Chrysler products.

 

[Howard Durand]

I think this problem is definetely an electronics problem. Most likely in the PCM.

Mine has done it a few times since it was new but not enough to make me try to correct it.

I did remove the temperature sensor cable and install a resistor trying to get the OD to be more predictable in it's shifting. I'm not sure if it is helping or not. Haven't had enough time to drive it lately.

I started with a 5K ohm resistor and it seems to shift later so I put in a 1K and am waiting to see how that works.

I didn't use any silicone to seal it though. I found a 3/8" ID rubber vacuum cap at Schucks that fits nicely over the resistor and cable end.

 

[snake]

Snake,



The resister tells the PCM that the transmission is warm enough for OD. That's all it does. Any resister value that does that will work so changing resister values will have no affect. The resister either works or does not work. Period. The temp sensor is a resister that changes value in response to temp.



I think the PCM that is used with the 47RH transmission has some sort of programming error. Changing it might or might not affect the problem. Probably not. The switch is overkill I think.



You should get some experience running it with just a resister in place of the temp sensor and see if that takes care of the problem without doing anything else. If the problem still comes and goes then you may have to have the PCM reflashed. You may need some patience to solve this if the resister does not do it. If there are no other odd things going on it is probably not a ground problem.



Transmission shops don't understand this problem because it only affects '94 and '95 Dodge Rams with the 47RH transmission. It might affect the 42RH and 46RH transmissions which were used in the gasser versions of those trucks, but I don't know that for sure. These transmissions are the last ones to have a mechanical governor in Chrysler products.

===============================



Well it's been 12 days now with the K5 resister, no proberms. I will keep the brown wire toggle

Switch for a back up ?

Thank, David

 

[snake]

I think this problem is definetely an electronics problem. Most likely in the PCM.

Mine has done it a few times since it was new but not enough to make me try to correct it.

I did remove the temperature sensor cable and install a resistor trying to get the OD to be more predictable in it's shifting. I'm not sure if it is helping or not. Haven't had enough time to drive it lately.

I started with a 5K ohm resistor and it seems to shift later so I put in a 1K and am waiting to see how that works.

I didn't use any silicone to seal it though. I found a 3/8" ID rubber vacuum cap at Schucks that fits nicely over the resistor and cable end.

I started with a K1 and when to a K5, I don't see any different in the shift. In your signatures you have A Modified Mystery Switch, what is that?

 

[Howard Durand]

My "mystery swlitch modification" includes the ability to manually unlock the TC as well as lock it.

A little different circuitry is used to accomplish that.

I used a relay and a three pole switch to control the TC circuit then added another control that makes sure it is unlocked when OD is shifting in or out.



I think I agree with Joe that the value of the resistor doesn't make much difference to the transmission but am not sure what the PCM thinks of the temperature apparently remaining constant.

 

[jtwcummins]

During a recent trip from San Jose to Carson City there was rain and snow flurries all the way. Combined with I80 thru the mountains being very rough I started getting weird electrical problems. The volt meter dropped like the grid heaters came on and shifting got erratic. I started to look at the problem when I returned home. I found the problem to be grounds. There are 2 grounds in particular, one one the left side of the radiator support and the other on the right between rad support and batt. The sheet metal screws were rusted. I cleaned the connectors and the sheet metal and replaced the sheet metal screws with one size larger stainless. Problem gone. The electronics on new vehicles is very sensitive to electrical noise and bad grounds cause major intermittent issues noise problems if marginal. If I am working on a vehicle I clean connectors, starting with the batt terminals and unplug and clean all the connectors under the hood. Then I redo grounds with new hardware. Use dielectric grease on the connectors to aid in moisture proofing. With very few exceptions this fixes intermittent electrical problems.

If you look at that fine looking grill on these Rams you notice they are also a huge water scoop when driveing in the rain.

 

[Joe G.]

I think I agree with Joe that the value of the resistor doesn't make much difference to the transmission but am not sure what the PCM thinks of the temperature apparently remaining constant.

So far all indications are that the temp sensor and PCM consider it as a go/no go situation. It is either ok for OD or not. I have observed no indication that shows that the "constant temp" is a problem. I suspect that it just trips a flip/flop latch in the PCM that the PCM uses to determine if the trans is warm or not. I really doubt that the PCM used in our trucks (especially the 47RH models) is fancy enough to even notice that the temp never changes.