Hello all,

This is my first post.

I have read a bit in the forums here about the code 628. Tell me if I have this correct. I have a 95 F250 HD, 460, 95k miles total and only 40k on rebuilt trans, and have no idea which transmission - I have gotten the Continuous Memory Code 628 about 3 times now, appx 1 to 2 weeks between each occurance. I have read about "limp home" mode and I have been to fordfuelinjection and understand how to read and clear codes. If I understand correctly, this code is either a sensor error of some kind or my converter clutch is really slipping when it should be locked. Here is my problem, from what I understand about the locking converter - it should only lock in OD when the ratio is near 1:1 (like if I am cruising on the freeway). I seem to get the code when the converter should not be locked - a couple of times just putting around on local side streets, and once while driving with OD off (towing). I also pulled the pan on the trans and everything looked very clean.

First of all - is there any danger in towing at this point - can I destroy my transmission if I continue to drive the truck? Second, how do I pin-point the problem rather than just throw money at it (like a new converter or tranny rebuild), do I start with sensors? BTW, the first transmission shop I went to tried to push me into a full rebuild and he estimated 3 grand - that is how I ended up at this fantastic website.

Brad

 

well first things first. WELCOME TO FTE!!!!!!

If you have a three speed with overdrive then your trans would be an E4OD
if it is a three speed then you have a C6

as for the trouble, i would check out your MLP/TR sensor at the transmission shift lever. disconnect the electrical connector and see if there is moisture in it. If so I would start with replacing it as it can cause many transmission problems with and without codes. when you replace it, install dielectric grease in the connection to seal out moisture. this grease can be found at most parts stores. I lean towards this because you have only 40k on the rebuild and most alternate transmission shops fail to replace the sensor much less update it.

let us know what you find. Where are you from?

 

The torque converter can be locked in any gear. All the computer has to do is ground TCC. The computer does this as a function of transmission temperature, engine load, engine RPM, engine temperature, and vehicle speed. The computer does lock the converter in at least 3rd and O/D. It might do it in second. It probably does not lock the converter in first. The lockup function is NOT blocked out when you select the O/D off switch.

If it takes 1 to 2 weeks to set the code, and you aren't rolling down the road with the light blinking angrily, and you can't sense any obvious shudder in the cab, then I wouldn't lose a lot of sleep over it. Feel free to tow away.

If the code sets in 3rd gear, there is a good chance the problem is due to the RABS sensor or the PSOM module, and is not due to actual slippage of the torque converter clutch. The lower gear provides less resistance to the torque converter, making it less likely to slip, at least under modest load/throttle pressure.

 

Thanks for the replies guys.

ponyracer: I live in LA and we have a lot of rain recently so a water problem makes some sense. I checked the cable and connector just over where the shift cable connects to the transmission (drivers side). I did not notice any water in the connector, should I disassemble anything to look further?

fefarms: Interesting, your comment about the light blinking angrily - I assume you mean the OD Off light which should blink when a code is captured - this has never happened. My only indication has been the hard shifts, then I run the self test and get the 628 code. The OD light never blinks - just on or off as usual. Does this mean anything in regards to the troubleshooting?

Brad

 

The lack of CEL or O/D lights suggest the problem is intermittant and doesn't happen very often.

Try collecting the codes once a day, hard shifts or not. See if the code 628 is being set even though the shifts are normal. It would be helpful to find out if the 628 is strongly correlated with the computer putting the trans into performance mode, or if the two symptoms are unrelated (hard shifts due to the MLPS or the phase of the moon or whatever and no related code is being set for some reason.)

The hard shifts are irritating to you, but don't hurt the trans. I would have thought the computer would exit performance mode when you shut the key off, but maybe it "remembers" the past history with code 628 and waits some number of drive cycles to go back to normal.

Does the shifting go back to normal if you pull the STI jumper during the 628 flashout? Or do you have to disconnect the battery?

 

no I would just reppace the MLP/TR sensor and add dielectric grease to the connection, that shoudl fix you trouble

 

Ponyracer,

The Ford TSB applies to 1998-1994 Vehicles, I have a 95.

LIGHT TRUCK:
1989-94 BRONCO, ECONOLINE, F-150-350 SERIES, F-47, F-53, F-59

Does this make a difference? I see there is a "TR service kit" available for this problem.

Brad

 

I dont remember that TSB. but If you go into a Ford dealer they will sell you the updated part with the new style connector. Then go to a parts store and get some dielectric grease to put inside the connector.

 

Make sure you pay close attention to the wiring diagram for the old to new connector, just transfer one wire at a time and double check each wire placement.

 

1994 Ford F250 XLT RWD 7.5

this is what mine is doing as well.

if i unplug my battery, and clear the memory…it shifts fine for a few days. Then starts to shift janky between 1st and 2nd

also get the 628 code

Start with a fluid flush and go from there?