Ok, as the title suggests, no reverse and it will go forward. I'm assuming the trans needs a rebuild. But, just to be sure it's not something I've overlooked....
5.4L, 4R100
2 or 3 years ago, I replaced my manifolds - the 'ol broken stud issue. Replaced with a set of shorty headers (wasn't easy, but I got it done) because I found a set for less than I could find the cast iron. (shouldn't have cheaped out!!). So, fast forward a bit... the driver's side pipe on the header broke and I didn't have the time/money to replace the headers again so I parked it. It also had a leak from "somewhere" - wasn't sure if trans or PS, and it was tiny.

I just started on fixing it since I have all this time on my hands due to current events. The starter was shot (we get bad winters and snow drifted and sat under it is my guess), battery and the previous issues. So, I changed the starter and put in a new battery, realized the AC was seized so I bought a shorter belt and a ribbed pulley and bypassed it. I do like my AC, but I really want the thing driving (So I can get it to a shop!!), and I'm willing to "suffer". Also discovered the fuel pump was dead (Confirmed by testing after changed). Anyway, she fired right up without so much as a snort of starting fluid, so I figure I'm in the home stretch.

I backed it out of the driveway and went up and down the street a couple of time (Open header and all - My neighbors love me!!) and figured I was ready to throw on new breaks and rotors and figure out a patch for the header (It's only a clean break, just trying to fix until I have more cash for good parts). That's when I re-realized the leak and climbed under and saw the trans lines leaking - well, spraying against the driver's side tire)

So I bought new lines and spent 2 days cursing them out as I tried to get the REALLY LONG top radiator to trans line installed. Went to back it off the ramps after putting in enough fluid to see it on the dipstick and it drove forward! I tried running it through 1st 2nd etc a few times, let it warm up for a while, kept checking the fluid level, no dice.

Only code I got (aside from obvious O2 codes) was a speed sensor code that I can't remember right now and the OD on the shift lever flashing.

Am I correct that it needs a rebuild, or is it something I may have overlooked?

 

If the shift linkage is connected and actually moving the manual valve in the valve body, then the only other possible cause of moving forward in reverse is a welded forward clutch. This happens when something causes the forward clutch to slip and the heat from slipping welds the clutch together. Low trans fluid from a bad leak could do this.

 

Thanks Mark, I figured it was scrapped and you've confirmed it. When I get the trans out I'll begin the autopsy. I'm running "vision impaired" on this - Found a YouTube Series called "Ford E4OD / 4R100 Class from a channel called Transmission Bench. It's well made and explains alot, so I'll be following his lessons whilst making a big mess in the garage. I realize that he is promoting a product (They sell rebuild kits) so I'm not planning to do the whole gigantic rebuild that he did (added shift kits and mods to it), but I am curious if there are certain parts (aside from frictions) that you would recommend for EVERY rebuild, and what parts - if in good condition - can be safely reused.

Thanks for the help!

 

I don't have any specific recommendations.