I've got a 2004 5.4 FX4 with 230k on the transmission, within the past year I dropped the transfer case to do some seals and everything drove fine for awhile. Then I started having issues in the cold starting/staying running that ended up being the crankshaft position sensor wire being chewed up. In the process of trouble shooting that I replaced the FPDM with a generic one. After a while I started experiencing issues shifting up with light acceleration where the truck over revs thru the shift and let's out a little squeal when it finally shifts. I usually let off the gas when I realize it's happening, it will continue to rev a little more and make the shift. When I drive mildly aggressive to full throttle it makes the shifts no problem. I swapped back to a motorcraft FPDM thinking it might've been the generic unit dumping gas at the wrong time but the problem persists. Would this be a symptom of the shift solenoids going bad/is it worth trying or is the transmission just at the end of the road?

Thanks!

 

Hows the condition of the trans fluid? If its good, then disregard that but if unknown I would change it.
Which shifts is it, all of them or just the 1-2, or 2-3?
I can't comment on the solenoids wearing out, but all those little check ***** inside the valve body do wear out and it seems like I've read a few posts where people saw improvements in small symptoms by changing them out I think I would try that out.
Other ideas are some of those sonnax shift improvement items might help you where you probably have some pressure leaking by somewhere and thats why it shifts better when you are on the throttle ( there is more pressure available)

 

Hey turbo, Appreciate the response and my apologies on the delay in my response. It is both 1-2 and 2-3 shift. I was a little high on fluids, maybe a quart for 25-50k, I can't remember when I changed it mileage wise but it was a year ago. I pulled some out of the full tube with a syringe, the fluid was ok, a little brownish but didn't smell burnt. I'm going to see if that makes a difference but I kind of doubt it, how difficult are the check ***** to change/sonnax shift improvement items to install?


Thanks!

 

That video shows the *****. I can't say that they have anything to do with your particular issue, but if you are going to drop the pan anyway it might be worth putting replacing those on your list?



​​​​​​sonax has a couple different kits. "Zip kit" and "the sure cure"
I have not had to use either of them, but I think I would research them if I was in your shoes.
https://www.sonnax.com/parts/4458-zip-kit

 

Turbo thanks for the video!

For anyone else following, I ordered a remanufactured sonnax valve body, I don't have the time to rebuild one. Went to swap them this weekend and my 2-3 accumulator spring just fell out in 2 pieces when I pulled the valve body and the retainer is pretty beat up/bent. I'm waiting for those parts to come in but still plan on putting the new valve body in as well.

 

Yikes that can't be good. Thanks for the update I'm hoping this work will get you back on the road! Let us know the end result.

 

I was reading your post about the shifting problem having high rev slamming into gear with a squeal afterwards I've got the same problem and was wondering what the outcome was that I've been looking all over and this is the only one that I can relate to 100%. I don't know if it can let you email me back or post me back but here's my phone number I would really like to talk to you about this.. 704-748-9871 and my name is Adam

 

I have a 2018 that threw P0757 shift solenoid b code and my 1-2 shift is complete trash , it sounds harsh like metal clunking together but in any gear above that it’s completely fine and normal. Checkout transmissiom oil today