kaboom10

The temperature guage I have is digital that starts reading at 72 degrees. Below that temp it blinks 'LO'. I have been getting fluctuations in temp reading as if there may be a thermostatic temp bypass in the cooling system for the trans or I have a sending unit that is goofy. I had the trans flushed and filter changed then had the trans temp guage installed. The trans is starting to heat up faster now at these temps than it ever has since I had the guage installed. I get up to about 125 and suddenly it's reading below 70 then it climbs back up to 125 and stays there for the most. Any ideas?

chad085

your tranny fluid runs through the radiator as well as an external cooler in its journey to stay cool. The opening and closing of the cooling thermostat affects your coolant temp, and with the tranny fluid using part of the radiator, those temp fluctuations are relayed to the trans fluid as well.

kaboom10

I noticed that but I thought it was always open. I've always owned an automatic for the most part and this is the first time I've heard of thermostatically controlled but of course this makes a lot of sense to warm the trans to get it to lockup the torque convertor clutch. What concerned me is the fluctuations.

dale7637

Not sure about the ford transmissions but some of the cat powershifts go into a cooler bypass. The fluid circulates inside the transmission case but not to the cooler circuit. If this is going on it can cause the temp to rise quickly, and then fall quickly as soon as the cooler circuit re-opens. I am sure that someone will correct me if i am wrong.