Transmission won't shift into overdrive when really cold

[Yeret]

Well, this is a problem that started up on me last winter and seems to have just surfaced. Basically, when the temperature is really cold (like, negative wind chills with heavy wind) the transmission randomly will not shift into overdrive. It shifts through all the other gears just fine but won't go into overdrive resulting in me having to drive 55 MPH at 2,500 RPMs. I checked the fluid when I got home from work yesterday (engine warm, in neutral, on the flat) and the fluid was full and red.

This particularly concerns me because this tranny was a $2,000 rebuild from a reputable shop with only 15,000 miles on it. Any ideas what's up? Or could this be considered "normal?"

Iowa winters suck...

 

[Merc225hp]

They will not shift into OD until they reach the right opt temp. You might have a faulty thermistor.

From the 2001 FSM, page 1897

Transmission fluid temperature readings are supplied to the transmission control module by the thermistor

The temperature readings are used to control engagement of the fourth gear overdrive clutch, the converter clutch, and governor pressure.

Normal resistance value for the thermistor at room temperature is approximately 1000 ohms.

The thermistor is part of the governor pressure sensor assembly and is immersed in transmission fluid at all times.

OPERATION

The PCM prevents engagement of the converter clutch and overdrive clutch, when fluid temperature is below approximately 10°C (50°F).

If fluid temperature exceeds 126°C (260°F), the PCM causes a 4-3 downshift and engage the converter clutch. Engagement is according to the third gear converter clutch engagement schedule.

The overdrive OFF lamp in the instrument panel illuminates when the shift back to third occurs. The transmission will not allow fourth gear operation until fluid temperature decreases to approximately 110°C (230°F).

 

[Relayer]

Tranny will not shift into overdrive until engine coolant reaches proper temperature. Check your temperature sensor.

 

[crazy_luck]

I've had 4 Gen 2 Ram 1500's since 2001 (2001 QC Sport, '00 Reg Cab Sport, '99 QC Laramie and a 2001 QC Sport w/ off-road package, in that order). Not a single one of them would shift into OD when temps were sub-zero, even when the first '01 I had was brand new. The only way to get it to shift into OD in sub-zero temps was to drive until it was fully warmed up, come to a stop, put it into neutral, shut the engine off and restart it - OD would work fine until it downshifted again going uphill or passing slower traffic. No garages or dealers around here had an answer as to why and coworkers that had same/similar trucks had the same experience.

 

[Rambling]

I've noticed my '03 Ram 1500 4.7 does this on the initial run after a cold start up. The last time I used it I drove 12 kilometres before it finally went into O/D. I thought I was having an issue myself before I read other threads on this forum stating it was normal until the transmission got to operating temp.

 

[dapepper9]

We recently had a child spell in the -teens and I had the same prob, had to drive 30 miles to work at 75mph and approx 28-2900rpm. That morning was -14°F and my dad's 05 duramax with the 5spd Allison did the same thing the same morning