i have a 97 mountaineer v8 aod,for the last 2 winters transmission slips when cold out on the highway,only when temp outside gets 30 or colder,pull over let it run 5-10 min runs great at 65 for about 8-10 miles then same thing,i put new filters twice and new fluid,i have put over 40,000 miles on it since it started doing,this,it doesn't do this in the summer,im lost,any help.

 

Do you have access to a scan tool that can datastream the transmission sensors, specifically the Transmission Fluid Temperature (TFT) sensor values? It would be interesting to see if, on a cold start in the winter, the TFT sensor is showing a fluid temperature quite a bit higher than the ambient temperature.

-Rod

 

no I don't have any scan tool,but since you said about sensor ,think maybe even when its cold its letting the fluid still go to the trany cooler???,might be letting the fluid get to cold and thickening up???

 

My thought was if the PCM thinks the fluid is warmer than it really is, it might be delaying the clutch pressures and causing the slip. Normally when the fluid is cold the PCM will be more aggressive with the shifts to reduce the amount of slipping in the transmission. Once the fluid warms, the PCM reduces the shift harshness by allowing more slip during gear shifts.

-Rod

 

o.k maybe I need to get it checked out,is there anything I can try,

 

Unfortunately the TFT sensor is part of the main control valve body so quickly accessing to see how the resistance changes over temperature is not a simple thing to do. If you're willing to try, I can attempt to find service manual information on wiring access points external to the transmission as well as the resistance chart so you could check it cold to see if it is reading realistically. Finding that detail in the service manual can sometimes be a challenge though.

Also, I trust that you've recently checked the transmission fluid level to make sure it's where it should be.

About the only other thing I can think of to try would be the check pressures which I think can be done externally but I'm not sure what all is required for that. It doesn't sound like a trivial exercise.

-Rod

 

thanks for all your info,i know quite a lot of engines tranys ect,never had I have one act like this,i am old school,lol,i did change fluid and filter twice,with nothing in the filter screen,no metal,but I did notice there is maybe sensors in the valve body,i took the pan off and thought it was odd to have wiring in there,the inside thermometer that shows outside temp when it shows 30-32 degree outside like clock work the trany will start to slip,whats strange is its in all gears and reverse that slip,when it gets cold again if I cant figure this out I was going to try and cover up some of the coolor just to try it,

 

My 450 is doing it, at 10,000 miles. Didn't start until I had it parked for a couple weeks without moving it. But has only done it a few times, and shifts very well.