possible auto transmission issue

[03ranger4x4]

Okay, this is something I keep forgetting to say anything about when I log on until now....finally remembered to bring it up while I'm here.

Ok here goes, sometimes on the colder days when I drove to work my ranger would act funny as far as the transmission. By colder days, I mean like 30~34 degrees, maybe sometimes a bit lower. (I live in northern Florida)

Now I never let my truck really warm up before I take off, it runs maybe 5-10 seconds TOPS before I put it in reverse and am on my way, which as far as I know its normal to do. I know letting your EFI engined car or truck warm up is not necessary like it maybe was for carbed vehicles.

At any rate, the road I leave my development on is a 2 lane highway pretty much. I get up to 60 mph before the temp needle even moves off the C. Now here is what is weird. The transmission shifts all the way up to fifth gear normally. And it is not slipping. (I even floored it one day and the trans holds, so it definitely is NOT slipping) but until the temp needle gets about just off the C, or at least starts moving up the transmission will NOT lock up the converter. I just sits in 5th with the converter open. It is very distinct when the converter does lock up, so i am not thinking the lock up clutch is bad...also If that were the case it would slip all the time not just when cold. Basically it acts as if the computer is not allowing the converter to lock up until the engine is somewhat warm. However, like I said its only on colder days... if its 50 or above on in the morning it doesn't do this at all. Goes up to 5th and locks up like it should.


I do not know if this is a normal function. Perhaps the ECU is programmed to do this to allow the trans to warm up quicker maybe? Anyone know for sure? Also if this IS something that should not be happening how serious do you think this is? And how can I possible start to correct it (Where to start)

Tran fluid (and filter) was changed at 80,000 miles currently has 98,000 on it. Trans fluid is clear red and doesn't smell or look bad.

 

[adsm08]

Well, there is a cold-start shift schedule that affects torque converter clutch operation. I don't remember the specifics of it, but fluid shear in the converter is one of the primary sources of heat for the transmission, so disabling the converter clutch until it gets up to a certain temp would make sense.

 

[exbass94]

It's not supposed to lock up when cold. It helps the transmission get up to normal operating tempp faster.

 

[03ranger4x4]

OK, thanks that answers my question perfectly. I honestly figured there would be such a feature on an electronically controlled transmission, but just needed to be sure. Didn't want to keep driving it like that if it had been a problem that if solved would have prevented more damage. Glad its just normal operation!