Not Shifting into Overdrive (occasionally)

[yonkerse]

First of all, this may get a little lengthy, but I'm going to try and be detailed and explain what I experienced over the weekend...

A typical week of driving is this:
Monday-Friday: Short 3-5 mile trips, all city driving with MPH right around 35. The car may shift into overdrive half a dozen times. Totaling about 50 miles. I rarely see the trans get warmer than 75-80 degrees.
Weekends: Head home, mostly rural/country driving, half high way, half two lane country roads totaling about 150 miles. (longest trips of an hour equaling 45-50 miles)

Last night, I drove home to work (1 hr drive) and everything was normal. The night was the coldest night we have had and temps got down to 28 degrees according to my car. Car has been sitting for about 7 hours, used my remote start and let it warm up. I let it run for about 5 mins (coolant temp is usually up to about 100 degrees in this time.) I get into the car and leave work. I pull out onto a 55 MPH road and head about 4 miles into a small town. While driving, after a mile or so, I notice my car hasn't shifted into overdrive yet and I'm cruising along at 2000 RPM while running 55 MPH. The tranny temp is right around 60 degrees..and I figure its not warm enough to allow it to shift in OD yet (I think I have read it needs to be 70 degrees?) I continue on, and by the time I get into town, the trans temp is right around 82 degrees, and the car never shifted into overdrive. I get through town, head out on another rural road, get to 45 MPH and the car shifts right into overdrive like it always has. Only had one chance to get through gears as I turn into driveway.

This morning was about 32 degrees when I was heading to town. Start my car for the 5 minutes, get in and head to town. Trans again right at about 60 degrees and my car wont shift into OD. Stop at the store, go inside for about 15 mins, come out and head home and the car shifts right into OD like normal (trans temp was right around 65 degrees). Car sits most of the day, head back to school and the trans works flawlessly.

Now I kept a close eye on trans temps as I am running an external trans cooler and I think this may be causing my issue. These are the coldest weathers we have seen yet, and I do plan on blocking it when I have time to fab up something. However, I know for a fact that my car wouldn't shift into OD last night when the trans was at 82 degrees.

On the other hand, today when heading back to school, (and outdoor temps around 35 degrees) the trans temp leveled out right around 125 degrees....which seemed reasonable and like the cooler wasn't keeping the trans temps too cold...

Should I be concerned with this? Is there a little leeway to when the computer thinks its warm to shift the car into OD? Open to any comments or suggestions!

Thanks!

[SSEiMan01]

Trans temp does have something to do with it going into O/D as far as I know. I would block the cooler to be sure, otherwise. 105k of babying seems kinda early for a rebuild to me, But I've seen stranger things happen...
Anyone else have any input?

[crash93ssei]

Are you sure it isnt the TCC? In our 03 the TCC doesnt lock sometimes for up to 10 miles of driving when cold. I haven't been paying much attention to the trans temp to see when it locks though.

I know it will be slightly different SSEi vs SLE but without the TCC locked up the 03 rides right about 2,200 RPM or so at 60 MPH.

[Jrs3800]

Does the TCC apply in 3rd gear?

as well for the 4T65E there is a threshold for trans temp... What that number is I am not certain of.. But you will want to cover that cooler... as well are you running a 180 T-Stat? and if so what are the engine temps( not the gauge, actual )...

The good thing about the 4T60E is that the PCM was not really looking for Trans temp, it was more concerned with engine temps... Had to hit a certain threshold for TCC lock..

[yonkerse]

It seems to me that the TCC is locking correctly. It does lock in third gear when I have been investigating it over the last day. Not sure if it was locking correctly when the car wouldn't shift into overdrive this past weekend.

I am running a 180 degree thermostat and the engine temps are right at 170-172 when warmed up and driving around.

Haven't had much opportunity to investigate the issue anymore. In the middle of finals week and have bigger things to worry about at this point! haha

Thanks for the input!

[crash93ssei]

Just to be sure it is the TCC locking, give it a little gas and see what the RPMs do. If the TCC is locked in then the RPMs shouldn't move much at all, maybe 50 - 100 RPM. If the TCC is not locked then the RPM would jump 400 - 500 RPM.

[Bing]

I've got mine (tranny cooler) completely covered up now. With your short trips you definitely need to cover up that cooler.
Another thing to remember is that it used to run at 190-195. So even if it gets up around 170-180 its still not as bad as what it used to be.

[viper8907]

I'd put money on it that the TCC hasn't locked up. In 3rd gear RPMs would be more like 2500 at 55mph. Like someone else said, the TCC won't engage until 70 degrees trans temp. I know that my car runs around 2000 at 55 (in 4th with no lockup). You can also test to see what gear it's in by moving the shifter to third. If it's truely not in OD, nothing will happen. If it's the TCC, it will downshift.