Engine/Transmission (1994 - 1998) NO Overdrive when cold

[starring]

I go to school at Michigan Tech wich in Houghton, MI for those of you who don't know where this is you just need to know that it is very cold. Does any one have any tips for getting the transmissoin to shift into overdrive other letting the truck warm up for 1/2 an hour or stalling out the torque convertor.

 

[Joe G.]

You don't say what year your truck is, but I think this applies to all of them. There is a temp sensor that prevents the shift to OD until the ATF is warm. According to my '95 manual the ATF must be at least 60 degrees before the PCM will let it shift.

 

[starring]

Sorry it is a 95 with an ATS transmiossion

 

[JohnE]

Set the park brake and the transmission in drive. The added load will warm the engine and trany much faster.



Me, I run the Espar and then start and fast idle the engine to make sure the batteries get a full charge before shutdown.

 

[TPotter]

While warming your engine, shift the trans into the nuetral position I believe its something to do with the lip seal needing to be warmed.

 

[AWray]

I also have a 95 with an ATS trans and torque converter. I dealt with Will at ATS and asked him about the trans not shifting into overdrive when cold. He thought an electronically savvy person could chage some wiring to fool the computer into shifting. Does anyone know how to bypass the cold reading from the temp sender. I know first hand how bad it sucks trying to run 55 with 4. 10 gears. I feel like I'm killing my poor truck.

 

[Joe G.]

I not sure if this will work, but it should. Disconnect the connector to the transmission temp sensor. Then put a resister with about 5K ohms resistance between the terminals in the connector end on the wiring harness. That should make the PCM see that the transmission has a temp of about 100 degrees. It should shift to OD and TCC lockup should work too.

 

[98rammer]

is this just on the 47RH's?? mine will go into OD once i get on the road after 1-2 minutes of idling in neutral... in 0* weather.



Tom

 

[Cooker]

Originally posted by Joe G.

I not sure if this will work, but it should. Disconnect the connector to the transmission temp sensor. Then put a resister with about 5K ohms resistance between the terminals in the connector end on the wiring harness. That should make the PCM see that the transmission has a temp of about 100 degrees. It should shift to OD and TCC lockup should work too.

This is correct.

 

[Cooker]

Originally posted by AWray

I dealt with Will at ATS and asked him about the trans not shifting into overdrive when cold. He thought an electronically savvy person could chage some wiring to fool the computer into shifting.

I can't believe ATS was not aware of how to do this

 

[jimk]

sensor

Originally posted by Joe G.

I not sure if this will work, but it should. Disconnect the connector to the transmission temp sensor. Then put a resister with about 5K ohms resistance between the terminals in the connector end on the wiring harness. That should make the PCM see that the transmission has a temp of about 100 degrees. It should shift to OD and TCC lockup should work too.

I did as Joe suggests here, I dont think the resistor was exactly 5k but it was close. I was told that doing so may not be a good idea but to let the transmission warm up. The sensor was leaking anyway and I dont like leaks so I pull it out and soldered in the resistor. Works great. One less leak, I have 95 k miles on the auto, so big deal. Take it easy on the auto when it is cold. Go to neutral when you first start up. Good luck Jim

 

[AWray]

Where did you find the resistor? Radio Shack or some place like that? After placing the resistor in the terminals of the sensor plug, do you hook the plug back up or leave it unhooked?



Does anyone know why the 47RH's have this minimum temp for overdrive engagement when the 47RE's do not?

 

[jimk]

resistors

Originally posted by AWray

Where did you find the resistor? Radio Shack or some place like that? After placing the resistor in the terminals of the sensor plug, do you hook the plug back up or leave it unhooked?



Does anyone know why the 47RH's have this minimum temp for overdrive engagement when the 47RE's do not?

I would not hook up the plug to the sensor, that would not have the same value as you need to do what you need. I cut my plug out and soldered in the resistor. But the sensor also I think takes the overdrive out if it gets to hot. Not sure, but I think. I only assume the cold oil does not lubricate good back in the overdrive unit, could be some other reason. I would go to neutral when I first start up and let it set while the truck warms up. Emergency brake set to be sure. Then I would ease into the gears while it is cold and not go to overdrive for a few miles to make sure the units is warmed up a some. Just an idea Jim

 

[Cooker]

Originally posted by AWray

Does anyone know why the 47RH's have this minimum temp for overdrive engagement when the 47RE's do not?

The RE's function the same way. The sensor is just in a different place.

 

[Loren]

What Joe said early in this thread is correct regarding the temperature sensor. After the transmission warms up, it will shift into OD. With my 1995 truck, this takes only about 1-3 miles with air temperatures of 20 degrees or so.



Regarding shifting into neutral rather than park: The transmission pump doesn't run with the transmission in park. This is why you must shift into neutral to check the fluid level. Obviously, the fluid will heat up faster with the pump running, so shifting into neutral will help.



If you really, really trust your parking brake, shifting into drive will slip the torque converter and warm the fluid even faster, as suggested by JohnE.



My opinion is not to override the temperature sensor. I don't know why Dodge wants that fluid warm before it allows the shift into OD, but I suspect they did not install that sensor (at some expense) for no reason at all. Until I know why, I'd leave it alone.



Loren

 

[AWray]

With my ATS trans & torque converter, I have to drive something like 10 miles before the trans will shift into overdrive on its own. If I drive for a few, maybe 3-5 miles, and then stop, the trans will shift to overdrive and then lockup. I still experience all of this after letting the truck warmup for 10-15 minutes. I don't know what it was stock since the trans blew after 300 miles in my possession.



I as told that because the trans is more efficient, (good under normal towing and driving, sucks when its cold) it takes longer to build enough heat to shift into overdrive.



What about a pan heater? I think I have seen them in Jeg's as an oil pan heater. I want to eliminate stopping five minutes into a trip especially when it's on the interstate and revving the motor so high.