I tried a search on this, but after about 45 minutes I still hadn't found anything.

In any event, a friend of mine who works for Ford heard that I was getting an Edge programmer, and asked what all it could do. When I mentioned that I could set the rev limit and transmission shift points, he said that with the 3v 5.4L motors the best WOT shift point is towards 6kRPM. I asked him why the factory set it at approximately 5kRPM, and he said that it had something to do with a valvetrain limitation. When I then asked him for details, he said that he didn't know specifically, but had been told that swapping 3v Mustang heads would resolve the issue.

Does anyone know where this limitation is? Is it in the valve springs, or rockers, or...??

Thanks for any input.

 

I thought the problem was the torque converter balloons above 5k.

 

Hmmm. That might be it, too. THAT would be inconvenient.

 

Some new information from my Ford engineering buddy:

Your torque converter is used in several other applications that rev higher. For example, crown vic and towncar non-police models shift at 5300 with that converter. The PN96 (old-style) F150 with the 5.4L-2v or 4.6L-2v shifted at 5250 rpm.

I've been told by several other ford engineers that the current f150 rev limit is set by valvetrain, but nobody has been able to provide more details. The trans calibrator that has responsibility for setting the shift speed for that truck doesn't even know the reason. This makes me highly suspicious. Keep in mind that a large chunk of engineers that work on trucks have the mindset "it's a truck, why would you want to shift it at high rpm?". This strongly discourages any projects that would attempt to raise the rpm capability of the powertrain. I'm going to ask around a little more at work... but I won't promise anything.

 

Double Post

 

Ford states the F150 5.4L 3V Redline is 5400 rpm.

I believe the Mustang 4.6L 3V uses the same valvetrain and redlines at 6250 rpm.

After some research it seems the limit of the stock Torque Converter is 5400 rpm. The 4R75W and 4R75E converters supposedly have brazed fins and a bearing and stand up to revs a little better than the 4R70E converter.

If exposed repeatedly to 5400 rpm+ they will loosen up enough to hit the converter housing and come apart.

 

Gene- thanks for the response... it's good to see that the issue seems to have been found.

 

There are aftermarket converters available for the 4R75E that are capable of 6000 rpm+.