I have a 2002 Ford F350 Super-Duty crewcab with a 7.3 Powerstroke. This truck has been very well maintained and not abused in any way. It only has 116,000 miles on it. I programmed it with the superchip and it runs great it also changed the shift pattern in the transmission also, i have ran it with the program in it on performance mode for about 50,000 miles with no issues and most of those miles were highway miles if that makes a difference. here lately the transmission has started shifting hard into the last gear anywhere between 40-45mph range. if i am steady picking up speed it shifts hard and almost makes gringing sound. but, its not grinding its more of a Grrrr... sound. kinda sounds like the torque converter is flexing or something, almost as if something is not in line. if i easily allow it to shift in the last gear it goes in preatty smoothly but it still does it. once it shifts into the last gear i dont have any problems with it, I can hit the gas a little bit to pass someone on the highway and it does everything that it is suppose to do perfectly.It downshifts fine and runs through all the other gears just fine, only the last gear is being a problem. I have only pulled a trailer a couple of times with it and the load that was on the trailer both times was only about 4,000lbs. but, that was over a year ago and it just started doing this about 2 weeks ago. I was told to put some Lucas transmission lubricant in it so i did, that has not seemed to help anything. I took the program out back to stock and it still does it but not as bad. I guess maybe the program finally ruined something in there, i dont know!! any help would be great and I would really appreciate it. Thanks for reading and taking the time to answer.

 

the throttle positioning sensor known as tps. if it gets hot your trans will not go into od. I've had a similiar problem except i have a 93 chevy c3500 6.5td with a 4l80e . I had my transmission rebuilt. well cutting to the chase. your pcm or tcm has to see a signal voltage
in order to allow the transmission to switch to od. most transmission from 93 on up regardless of make of vehicle have electronic solinoids. your tps produces that signal voltage. I found a fix on the internet applied to a dodge diesel tps. in your situation the voltage may be different. but at least it will buy you some time before replacing the tps. for my truck it's about 160 dollars your truck may be more. I don't know how to post pictures on this site,but if you drop me an email at cool78259@yahoo.com i will send you the diaghram. all the circuit requires is a 3 dollar potentiameter and wire you can get at any electronics store.

 

i had a similar problem the shaft in the transfer case that runs from the input to the output came loose i had to replace my trans case it was shifting hard then all of the sudden i stopped moving and nothing i did helped me so i checked some things out and it was the trans case.

 

If its not shifting to od its simply the tps at fault

as for the sound : its prob metal on metal
-im assuming u've check ur tranny fluid...

 

If it's not shifting smoothly, then there's more at fault than the TPS. But it sounds to me like the trans is dying. Most likely from the poor trans tuning in the Superchips...

 

any codes? ant metal flakes in tranny fluid? or does the fluid smell burnt or dark? if so simply changing the tps will no longer be the only repair. check these things out, if you have a code let me know