I have a 2000 SD F250 7.3 PSD SWB CC 78,000 miles. My Trans temps are starting to soar. Today it was 75 Degrees and without towing anything just out romping around the temps got to about 215. I have an aux perma cool trans cooler in replacement of the factory unit. This model truck did not have the Raidiator cooling section. The fluid has been changed recently and looks and smells good. I also have installed the TC manual lock mod and it dosent feel like the tranny is slipping. Anyone had this problem? What are your trans Temps?

 

Once, after I had just gotten back from having transmission work done. The line out of the bottom of the cooler to the tranny had gotten kinked. Temps like that you've got to have some kind of obstruction. If you're lucky it's easy to fix like what I had. If not, I think you're in for a little investigative work.
If you know where the bypass line is you could pop that off the tranny and run the truck for just a sec. If fluid comes out of the line you'd at least confirm that you've got an obstruction.
I'll rely on others to give more. I'm not trying to be incomplete but I don't know anywhere near as much on this as I wish I did.

 

You need to run a cooler flow test. Remove the cooler line where it attaches to the rear of the trans. Have two buckets handy. Put the line you removed into one bucket. Have someone start the engine. Once the flow is steady move the line to the second bucket for exactly 15 seconds, then put it back in the first bucket and shut the engine off.

If fluid comes out of the trans when you are running this test, it fails. If there is not at least 1 quart in the second bucket, it fails.

If it fails, there are three possibilities. It could be a plugged (or partially plugged) cooler, a bad bypass, or a worn out pump. The pump is by far the least likely cause, but it is possible.

And where is your temp sender located?

 

I will do the test, But the cooler is brand new! I also installed the perma cool aux trans filter could this be the problem? I have confirmed the flow direction is correct. The Trans Temp Sender is located on the driver side port of the trans.

 

did you have the gauge before you did the cooler? if so what did it run at then? do you have a alloy trans pan with a senser port? thats were you will get a true oil temp.

 

Cooler flow test Complete! 15 seconds +- 1-2 almost two quarts. no fluid coming out of the tranny either. Took it for another drive about 15 miles with a stop inbetween and temps were at close to 170. This was from bone cold. the temp here in Texas today is about 72. So what do think Cluthches? TC? Both? I am liking the looks of this.

 

On this run your temps are about 100°F above ambient. That's normal. Depending on where your temp sensor is located, it might even be on the cool side of normal.

 

The problem with that theroy is that this seems to be dominoing. The last trip I hauled anything on I had a GTVW of of 16,000 and the temps never exceeded 200 and that was on a 250 mile trip. It didnt even get to 170 until the end of the trip. and the weather was hotter. Now with no load it gets hot in 15 miles. According to the ambient temps it should be cooler especially with no load.

 

I think I agree based on you upgraded the cooler and you're hotter than you used to be. Ford says you can be 200 and fine. Personally, I think thats plenty warm, but on a stock tranny and a stock cooler, it was also typical. But I shelled out 2 stock trannys before I hit 80K for miles. So my preference, at least, is to be cooler. Way cooler. I can't say that temps contributed to my woes, but they didnt help.
I'm coming at it from a very different perspective now though. The BTS tranny and the 6.0 cooler, my typical road weight with trailer is at or slightly above 21000, and at 70 degrees ambient I might hit 130 for trans temp.
Don I already said I'm not a tranny expert. I'm the guy drinking his soda going well heres an guess based on imcomplete information. But I think I'd keep nosing around until you either find something or just the sheer volume of evidence tells you that there really isn't anything amiss.

 

When your trannys went south, what kind of evidence did you find? flakes in the tranny fluid? discolered fluid? High tranny temps? I think I am on the road to a BTS, But I would like to dodge the 4,000 Dollar bill if I can.

 

Well the first one was obvious as all get out. It stopped moving. After making a strange sound. It got towed, one of the gears had gone to heck. The whole thing was tore up decent I guess and I got a new one. The second I was just losing power enough that I could tell. I didnt know what was going on but one of those things where your gut says you're buying a transmission again. And I took it in and said ok, temps are going up, power going down, I dont feel like I'm putting power on the ground.
They came back and said well its still running. But your TC is slipping way too much, you've got a lot of garbage in the cooler, your fluid is getting kind of nasty and it isnt very old, technically, you could drive out of here, but you'll be back on a tow truck in three months with what you do to the truck. And I said, I'm calling Brian. And, that was that. I dont like spending the money either but I figured if I was buying a tranny I was going to get one I wouldnt sweat about. So each stock one, right at 40K miles was its life.
In talking to Brian after, (he takes the cores back) he said on the phone he hoped I'd flushed or replaced the coolers because, in his words "you left a lot of clutch back up there with you". So I took that to mean the TC plates were shot.

 

"The second I was just losing power enough that I could tell. I didnt know what was going on but one of those things where your gut says you're buying a transmission again. And I took it in and said ok, temps are going up, power going down, I dont feel like I'm putting power on the ground."

This is exactly what is happeing to mine!