Just as the title says, my 2000 F150 only slip when hot outside. During the winter the truck shifts perfectly but when summer comes it starts slipping and has a hard time keeping up with traffic. This has been going on for 3 years now. I don't have a check engine light on or any codes to be read. I replaced the solenoid pack, transmission fluid and filter and installed a transmission cooler with electric fan and it still slips..

I've been told the transmission lines are to close to the exhaust pipes which of course would overheat the fluid so as a test I'm thinking about running the transmission lines with a valve inside the cab into an ice chest filled with ice. The valve will be used to bypass the ice chest so in theory when the transmission is slipping I can turn the valve and flow the fluid through the ice chest cooling the fluid and if the transmission stops slipping then my fluid is obviously getting to hot.

I've heard short track bracket race cars have similar set ups. Has anyone heard of this or maybe tried it themselves? Pulling out what hair I have left on my head at this point.

 

Sounds like it's time for a rebuild.

 

But after 3 year I think it would be getting worse. The funny thing is if it survives this Phoenix summer I bet it will start shifting normally as the weather cools off.

 

1st thing I would suggest is a TRANSMISSION temp gauge.....what is hot?

btw add sender to TEST PORT in transmission (recommended) then a couple tranny guru's here can probably give you some useful info.

 

That's a new one on me but an excellent idea. I will look into a temp gauge tomorrow. Now where is the TEST PORT on a 4r100?

 

There's already an internal temperature sensor built into the transmission. Use your scan tool or OBDII adapter/app to read it.

 

Have you tested anything on the transmission? Pressures? Flow rate?

 

Have you considered a larger transmission oil cooler?

 

[QUOTE=Nun Ya;5252368]Have you tested anything on the transmission? Pressures? Flow rate?

I have not tested any thing due to me working so much.The transmission slips so bad that I'm almost half throttle leaving stop lights just to keep up with traffic. The truck has over 200k miles on it so it's probably more cost effective in the long term to just buy another truck. I don't have the time, tools, space or knowledge to rebuild the transmission so I think it's about time to give up.