I have spent hours reading the previous posts about the dreaded P1728 code. But my situation is unique in the fact of how it started. With some background information, I hope the good people of this forum can help me make an educated decision.

My wife’s truck is a 1997 F250 HD with the 7.3 diesel. It currently has 356,000 miles on it. Not sure if the tranny has that many because we bought the truck used. She was driving it daily with zero issues. She backed out of the driveway last week and shifted to drive and nothing. No forward or reverse gears. Just like it was in neutral. I hooked it to my tractor and towed to my work shop. I found she had a cooler line that rubbed a hole in it on the exhaust and lost most of the tranny fluid. I replaced the cooler line and refilled the tranny with Farm and Fleet brand Mercron ATF. I did notice quite a bit of fuzzy metal on the magnet in the pan. All seemed good for a couple days. Shifted fine, no noticeable issues until the blinking OD off light started. She drove it home and I put my scanner on it. Had a intermittent CPS code and the notorious P1728 slip code. I replaced the CPS and reset the codes. Two days later the blinking light came back but this time only the P1728 code. I reset it one more time and it again came back two days later. So obviously there’s an issue. Although the tranny feels fine after the code is reset. So here’s my questions. Could it be the cheap fluid causing this? Should I try a good quality synthetic fluid? Or does it make since to just replace the torque converter and see if I get lucky? Or am I wasting time and money and should I just get a new tranny and torque converter.

I'm not opposed to putting a Monster Transmission in it but don’t like spending money that isn’t necessary. Hopefully the experienced gurus on here can help me make a sound decision.

Thanks in advance.

 

Take off the bellhousing cover and look at the front of the torque converter. Has it been discolored from heat? It will have a bluing effect if it overheated. If it has that, the converter is done. If not, the problem is probably not the converter.

 

Thank you for the response. I’ll check the converter tonight.

 

OK. I just pulled the inspection cover off and did not see anything that looked discolored from heat. The flywheel was blocking most of my view of course but nothing looked like it got unusually hot. I manually turned it 360 degrees and did notice I do not have a drain plug in the torque converter. From what I’ve read on forums is that these trucks did come with a drain plug on the converter from the factory. If that’s true, then my suspicions are correct that this is not the factory converter and possibly the tranny has been rebuilt/replaced at some point in its life.

if the converter is good, can the fluid be the culprit?

 

It is possible, but not really likely.

That converter did have a drain plug from the factory, so this is a replacement. I suspect there is an internal leak somewhere, robbing the converter of enough pressure to maintain lockup. A teardown is the only way I know to find it.

 

I assumed if there was a problem in the tranny it would have been caused by running it low on fluid from the leak. But it sounds like you are thinking it has lack of pressure to fully engage the torque converter. So the only thing that happened from the time it was low on fluid is me dropping the pan, cleaning it, changing the filter, and refilling the fluid. I also fixed the leak of course. Im trying to think if anything I did could have created the lack of pressure. I used a WIX filter. And admittedly cheap fluid. Is it worth getting a better filter and fluid and doing it over? Or are you saying I just need to bight the bullet and get a new/rebuilt tranny?

 

The wrong filter can cause this. There are different filters for 4x4 and 4x2. So could a problem with the o-ring on the end of the filter. I've never seen cheap fluid do something like this. If it said it was for MERCON use it is probably OK. But MERCON V would have been better for long life.

The only way I can see the fluid causing this is if it doesn't meet MERCON specs and is "slipperier" than MERCON is supposed to be. SInce Ford hasn't licensed ANY production of MERCON since 2006 you don't know what you're getting if you buy a fluid that says it is for use where MERCON was specified. There is no spec that defines that, it is whatever the fluid manufacturer wants to produce and sell. Conversely, a fluid that has a MERCON V rating has to meet the Ford MERCON V spec and be licensed by Ford to produce the fluid. There are controls as to the properties of those fluids. Anything goes for a MERCON fluid.

You could have damaged something running without fluid. The pump could be damaged and not be able to produce enough flow, so pressure is low. That is a bigger probability than the wrong fluid causing this.

 

Another consideration in this case is that P1728 does not necessarily mean that the torque converter itself is at fault. The earlier E4OD-equipped trucks had computer control systems and transmissions that were unable to discern between torque converter slip and a slippage elsewhere in the transmission. They did not have turbine speed sensors (found in the 4R100) that would allow the computer to determine what element was slipping.

The set criteria for p1728 requires that torque converter clutch to be applied (or at least commanded to be applied) and then uses the engine RPM and vehicle speed sensor inputs to determine if there is a calculated speed mismatch between one end of the transmission and the other. This does not mean that the problem HAS to be in the torque converter.

 

I’m pretty sure the filter was correct. It was identical fit form and finish to the one that came out. I made sure the old o ring seal was out and felt the new filter Snuggly slide into place. So I doubt I’d get lucky and replacing that again fixing it.

Your right about the fluid but I was just being hopeful.

With that said, I’m down to replacing the tranny and torque converter. I was thinking of going with the Monster Transmission called Black Beast. Mainly because they’ve got good marketing and it worked on me. But is there any recommendations of other companies to look at? Or do you think this is a good option for me? I’ll be doing the installation myself to save a little money. All my trucks work on the ranch. They pull hay trailers and the occasional tractor. So I want something that can work hard with longevity. Truck does already have an aftermarket trans cooler as well.

Thanks

 

Thanks for the info Cleatus 12r. With that said, is it still safe to assume it’s something wrong with the trans or torque converter? Considering how this all started with running extremely low on fluid. Plus I’m currently not getting any other codes. Now admittedly that code came from an Actron 9910 Pro. It can read KOEO codes on this truck but not KOER codes. However the Delivery man just brought my new AE scanner yesterday. I haven’t even opened it yet. Is there some other things that scanner will show me that I can confirm the tranny or torque converter are at fault?

 

If you didn't have the problem before it was run out of fluid, then it's safe to assume some friction material somewhere was damaged and it doesn't take very long to do so when run low on fluid.


You will not be able to tell where the P1728 is coming from but I think (hard on the "think" part) that there is a datastream value for transmission ratio (or worded similarly) that will show the calculated ratio in the transmission based on the PCM calculation of engine RPM and the Vehicle Speed Sensor. You will have to be in 3rd or 4th with the torque converter clutch applied and keep an eye on the value. It SHOULD NOT change under steady-state driving going into hard acceleration. This test won't confirm exactly where the problem lies however, just that there is a failed component somewhere. The applied elements in the transmission aren't different between 3rd and 4th other than the application of the overdrive clutch so if it's slipping in both 3rd and 4th it's going to either be the torque converter or one, two, or three other clutches.

If your scanner says "P1728" then that's what you have. No other scanner will tell you different but as you've found, bi-directional controls or diagnostic features may or may not function.

 

I had P1728 slip code in my 96 F250 PSD E4OD but it wasn't any clutch or TC.

It was the L/R sprag failing but finally showed itself when I had no forward or reverse a couple of times before I OH'ed the trans.

Symptom was that truck would come to stop at a light, push on go pedal 2-3 times before it would move again.

 

Alright. I’ll play with the scanner a little. But with yours and Marks help, it sounds like we all are pretty confident something was damaged in the tranny or torque converter. Based on how the trouble started. Because yes, there were zero tranny concerns prior to running out of fluid and even now, when not in limp mode, there are no noticeable issues. It shifts perfectly fine. But I did find a significant amount of metal particulate on the magnet.

With this information, and the expert help I’ve received on this forum, I’m confident that a new or rebuilt tranny and torque converter is what I’m facing.

Is there a preferred or recommended transmission option? I’m pretty sure purchasing one and installing it myself will be my cheapest option. But I also don’t mind spending the money in the right areas. Like getting a built tranny and a better than factory torque converter.

 

All i can add is if you do go with a rebuilt transmission, DO NOT get a Monster transmission.

There’s all kinds of negative reviews about that place and possibly a class action lawsuit being formed

 

I am familiar with the Dieselsite transmission. They build a good unit.