I own a high mileage (300k) 4WD 5.4L 1999 F150, 4R70W. I'm in Wisconsin, and during the horrible cold snap last week I noticed switching gears was sluggish. Take 15 seconds or so to engage into Drive for example. Since it was -20F outside figured might be due to that. Unfortunately I eventually completely lost the ability to go in reverse few days later (shifts to reverse, but got no movement). So drove it into heated garage and started trouble shooting once it warmed up.

I measured the line and epc pressures off the transmission. The line pressures were all at low end of specification, but in spec. The EPC line pressures were all nearly zero at idle (out of spec) and at low end of spec at wide open throttle.

Dropped the transmission pan and started inspecting. Very little experience with transmissions, so lot of youtube videos and how-to book buying. Removed accumulators, springs and snap rings fine. Transmission fluid looked ok, minimal metal shavings. Replaced all three solenoids as long as I was in there, EPC, shifter, etc. Tested shifting itself, rooster tail notches dropped in correctly with the shifting into different gears. Manual drive pin had free movement in control body.

Put the transmission cover back on and filled up tranny. Test drive started out fine, had reverse, and all gears. When I got out on the highway, noticed I could not get into high gears, 1st, 2nd worked, then after five minutes, lost 1st and 2nd as well, no forward motion. Ironically, reverse is fine now. This time backed up the truck into heated garage. Took pan off and did a quick visual inspection, nothing obvious.

Not sure where to go from here. Looking at service manual the control body is one of the possible problems, thinking about buying a rebuilt one for about $60 and popping in. Easy enough to do but not sure if cause of problem. Could be trans pump or clutch as well apparently, but that would seem to be much harder to get to and most likely better off with a used transmission put in. Looks like I could get a used 130k trany near me for about $400 but really dont want to do that job unless really necessary. Any suggestions really welcome, thank you for reading. Odd, that its not consistent, loosing reverse than getting reverse back and now no drive.


First photo before I did any work.

Current photo.

 

The problem is with the forward clutch.

It was failing when you had the delay in drive, you lost reverse because the forward clutch eventually welded down and couldn't release for reverse ending up in a bind up, lost overdrive because the forward clutch has to release for 4th gear. The clutches broke free after the fluid change and are damaged to a point they cant hold at all and you ended up with no forward and reverse magically returns.

Don't buy any more parts for this one unless you decide to rebuild it yourself.

I rebuild these all the time with less than 130k on them so be weary of a used one.

 

Thanks! Sucks its not something easy.

Few questions: Does a failing forward clutch explain the low EPC line pressure at idle (measured at the test port on the tranny)? or is that possibly the cause of the clutch going bad? Considering doing the rebuild ourselves, found some rather extensive "how-to" videos on you-tube on it. Luckily, the videos appear to show the same failure I apparently have. If I go that route, do you recommend any parts or rebuild kits I should proactively buy? Anything to watch out for?

I'm worried I fix the forward clutch but it just goes bad again because I didnt fix the route cause of the problem. In the video, there is a loose bore (causing lack of seal) in the overdrive piston that causes the issue, murdering the foward clutch. Common cause?

 

As a kid growing up,I spent a lot of junk yard time with my dad. He taught me how to wrench by taking off parts he wanted. After pulling it out at the junkyard, it was a breeze to install once we got it home. Good times. I understand why guys like to buy used auto parts. You do the work yourself, and save a little money.

It's a good theory for something like a wiper arm, maybe back jump seats in a station wagon, a seat belt buckle, sun visor, door handle......I watched my dad install 4 used radiators on the same car. They all failed eventually. I installed a new radiator into that car, and it didn't have to be replaced again. Needless to say, radiators, like transmissions, are wear items.

Trust jk080. These transmissions all fail eventually. You do not want to install a used transmission, only for it fail, and then you will be stuck with replacing that one. With these 4RXXX transmissions, the options are rebuild, or remanufactured. I'm sure that there will be people who favor rebuilding. And others will side with remanufactured You can do your own homework there. Maybe you have the knowledge, experience, and skillset to pull the transmission and rebuild it yourself. The rebuild kits are available.

 

Thanks, definitely understand what you are saying. I am considering doing the rebuild on the tranny myself rather than getting a used one. Money is an issue right now unfortunately. I'm unsure if my do-it-myself rebuild trans would be better than a used transmission of unknown quality. Kind of gambling either way really.

 

I dont do EPC pressure tests on these, I have but its been a while, from info that I have EPC pressure is normal from 0 to 93 psi. Since reverse is good that tells us that line and EPC pressures a sufficient.

Forward clutch failure is common for this transmission, the clutches can just deteriorate over time, the lip seals on the piston can fail, even the drum itself can crack. Yes this transmission suffers from a worn OD servo bore in the case that can cause forward clutch failure and the pressure regulator valve wears out the valve body, so there is a lot going on that contributes to the failure of the transmission. This transmission is known for worn bushings, broken snap rings, worn valve bodys and case, worn or broken forward and direct drums and converter issues. If you choose to rebuild it there are a lot of areas that need to be looked at to have a long lasting repair.

I dont know of any "rebuilt" valve body for this thing that is around $60, just the oversized PR valve that we do on EVERYONE of these is around $70.

 

Thanks for everyone's help with this, my first transmission experience. I ended up getting a used transmission with about 130k miles, and after many hick-ups related to full seating of the torque converter, have it up and running. Seems fine so far. My truck has nearly 280k miles on it, I'll probably need to change vehicles pretty soon, but at least it doesnt have to be right now.