Scott:
As it was explained to me, The bypass valve is there mostly for the benefit of the tranny. The rear of the tranny is lubricated by the oil that returns from the coolers. Therefore, if the coolers plug, the rear would be starved of lubricant, Therefore, the bypass valve would sense the increased oil pressure because the coolers are plugged, and the valve would pop open to provide lubrication. Thats the long way of saying yes, install a new bypass.

The cycling of the fan which indicates a bad serpentine belt and tensioner is a few seconds or so frequency, whereas the normal fan clutch cycle is much longer. You can tell the difference. This is best taken to Ford, not elsewhere.

I was thinking that while Ford checks and fixes the belt you could also cover the tranny history. I doubt they will find any mechanical failure, but you will be taking out insurance. You may also determine whether they or someone else should be your new tranny shop.

I once took my truck to a local tranny shop to drain it and install synthetic fluid. They said that the torque converter didn't drain, so a third of the old oil would be still in there and it would take 2 or three changes to get it mostly the new synthetic. There is a procedure which, if carefully followed, displaces the old oil out of the torque converter in one pass. I abandoned that tranny shop, printed out the procedure and took it to my Ford dealer along with the synthetic. They just charged me the time it took. Your new T/C may have a drain plug in it, making it easy to switch.

Finally, if all the fixes don't result in your tranny temperature staying below 200 all the time, you might want to switch to synthetic, which resists higher temperatures without breaking down. Be sure to get Mercon compatible, not Mercon V compatible or a combination fluid said to be compatible with both. Ford says their new Mercon V is now compatible with the older trannys like ours, but who knows when a shop runs out of the old Mercon V and switchs, and who knows if the independent oil suppliers really change their Mercon V compatible stuff or just say so. Mobil 1 has been ok in the past; I found it this winter in parts houses in Tucson.

Warren

 

Warren,

My trans guy is planning to pull the pan to check for any sign of clutch wear or damage. If he finds any, he said that he will be glad to tear it apart and rebuild it. Is this reasonable? Will he see what he needs to?

Scott

 

Welll; 1: New fluid. 2: Fix belt and tensioner. 3: New bypass. 4: check clutchs and SEALS. Rebuild. 5: Be very sure the coolers are not plugged. That should do it if done right. But this is the guy that failed to check the bypass. Try it and see.
Warren

 

I think that is reasonable, you might see if you can get him to extend the mileage warranty some. We all make mistakes at some point in time, if he is willing to make good on it, I'd go for it.

Also, don't remember if you have any extra coolers on your truck or not. If you don't, then 200 sounds pretty normal for that load. I strongly recommend getting an AUX cooler like the 6.0 tranny cooler or a big TruCool. Both will do wonders on the temperatures that you are seeing.