We need to replace the trans in my son's 2006 FX4. I'm hoping to find either a good low-mileage used (and take a chance on it) or a rebuild. We'll do the R&R ourselves so I want to make sure I get a drop-in match with all the controls in the right place etc. Other than making sure we have the 55E or 55w (depending on which it has) is there anything else to watch out for?

Thank you in advance for any guidance or suggestions.

 

If transmission has a dipstick to check fluid level its a 55E
No Dipstick is a 55W, it has a nut/bolt setup in center bottom of trans pan to check level and fill, unless there is a skid plate I wouldn't like that setup in 4x4, lol

Wiring is the same on both, 2001-2011, plug and play, so you could use either

Besides the dipstick thing the 55W has wider ratio, so higher ratio 1st , 3rd and reverse, 4th and OD are the same
Neither has 2nd "gear", OD is turned on when in 1st to get a faux "2nd gear" ratio, works just fine, and you get a 5-speed from a 4-speed by turning on a solenoid
This was first done by off-roaders using the A4LD, to make their 4 speed a 6 speed, its where Ford got the idea

 

Great info - thank you. I found the Federal code on the door and tracked it down to being the 55E. Also learned it has LSD 8.8 rear with 4.10 gears. I'll bet after 248,000 miles there is not much "limited" about the slip of the rear diff, though. :-)

Now to track down a reputable shop for a rebuilt unit...

The issue we're having is that it shifts just fine until it gets to highway speed. Then if you slow down and it down-shifts, it won't upshift again without a late shift and a "bang". If I shut off the engine and restart it, it seems to "reset" and works fine until I repeat the process. makes me think its an issue with a solenoid or something controlled by the computer...

 

It should have some transmission codes in memory
Need an OBD2 code reader that can "see" transmission codes, P0701 to P0802, most readers can't see them
I got a BlueDriver OBD2 reader, its a bluetooth model, a few years ago, no complaints so far, used it on many different vehicles not just Fords

Partial OBD2 code list seen here: https://www.therangerstation.com/tec...trouble_codes/