This post brought me here. https://www.ford-trucks.com/forums/1...s-testing.html
Using this to help diagnose this further. Thanks to @subford ! If he can chime in here that would be great.

Here is the run down:
1994 Ford F150 5.0 E4OD
Purchased at auction, 1 owner vehicle with 162,000 miles on it. Trans issue was apparent at purchase.

Current issue: Shifts slightly hard from 1st to second and a little from 2nd to 3rd. After that, mostly smooth sailing.

I've replaced the following

1. VSS - Motorcraft replacement - Figured easiest solution
2. TPS - Motorcraft replacement - Figured next easiest solution
3. U Joints - Rear Drive shaft - Spicers - Decided to do it because it shifts into gear hard when going from park to drive but that seems related to this issue as that goes away when I disconnect and reconnect the battery.
4. PSOM - found a rebuilt one on ebay - issue improved but didn't go away.
5. MLPS - Couldn't find a motorcraft replacement, Power Torque from O'reillys - again, issue improved but not gone. Has become more so intermittent I believe.

Some intersections I take off and it's fine. Others not so. Maybe 3 out of 5 intersections it shifts a little hard.

One thing I've noticed is that, when I disconnect the battery cable, then reconnect it, and drive. Of course it's good for a while and shifts like butter. To be expected. What I've also noticed is that if I stay under 40 mph, I don't believe the issue comes back. It's only when I go up to 60 and more so up hills that it comes right back, almost instantly. I wonder if I stayed on flat ground, it might actually not come back.

I believe it's one of these top 3 that could be the solution to the issue:

1. Tone ring - I just replaced the rear diff with 75-140w and sealed it back up. During that, I checked all the teeth and put a rag thru each tooth to clean it up. Thinking maybe some debris got on it or some surface rust that I can't see. No damaged teeth or surface rust found. No metal shavings in diff. I wiped down the tone ring and sealed it all back up. Installed fluid. That was 2 weekends ago.
2. Spacing of VSS from tone ring - I just installed it when I got it but from what I read from the previous post, I should've checked spacing when I had the diff open. I didn't know at the time to check.
3. Axle bearings? I haven't checked them and I don't believe they are showing any signs but I intend to inspect them soon.

I know the other options could be:

1. Vacuum line - I doubt because every electronic item I've replaced, it seems like it's gotten better. It's less of a hard shift.
2. ECC - Hopefully not but maybe
3. One of the connections to the ECC - Have yet to disconnect those and clean them with electrical cleaner.

I plan on doing the following to further diagnose.

1. Pull codes again and see if they've changed since the last few times.
2. Inspecting rear axle bearings, see if they make any odd nosies or the tire shimmies at all.
3. Lift rear end and run truck up to 30 MPH, while hooked to multi meter to the connection next to the EEC plug under the hook. Monitor the AC voltage
4. Lift rear end and run truck, check rabs module HZ on pin 10 and pin 3
5. Also might disconnect rabs module and drive it. See if issue goes away or not.

I'll post again soon with the codes. I forget the last few times I checked, what the codes were. All I know is they were the same codes. Maybe with the MLPS changed, things are different.

 

I pulled codes and sure enough, got a new code. Old ones gone. I looked through my notes and found the previous codes:

When I first got the truck I had:
157, 452, 658
Then after some updates:
452
And now I have:
628 - torque converter slipping

I really don't believe the torque converter is slipping. Seems to be fine when the reset everything.

 

I believe the torque converter is slipping.

If you remove the inspection cover from the front bottom of the trans you can see the torque converter. If the converter is slipping when it should be locked the front face will get blued, similar to the bluing on a gun. It only takes 50 RPM of slip to set the code. Can you detect that? I can't. The computer can.

 

if that ends up being the case like Mark says, yeah PCM might be picking up some slippage, either you can tear down and rebuild (I would recommend that). cheaper/braindead option that I tried was Lucas stop-slip, can't remember the exact product name off the top of my head. comes in quart bottles, adds some "grip" to the fluid to compensate for worn clutch material. I was slipping bad in third gear and fourth couple years back and my PCM threw 628... less mechanically inclined me back then was like f$#k it let's try some of it, I had the fluid/filter changed by a shop I trusted, in place of two quarts of mercon V they put two bottles of the lucas in. haven't had a problem since, no slipping, torque converter stays locked, it's been years and over 30k + miles since.. no I don't recommend doing this because there is no such thing as a fix in a bottle, but I tried it, and so far has bought me time and mileage to help me save for a proper rebuild.

 

Thanks @Mark Kovalsky and @Da_Lariat_Chariot.

I'll double check the things listed above but from all the posts I've read, many Mark posted on, does seem like a converter is in the mix. Seems odd since it drives fine till the code is thrown but transmissions aren't my area of expertise. Makes me think it's more of a sensor issue or electrical.

In any event, I'll try the things I mentioned, I'll check the converter per Mark's suggestion, and see what results I get. At this point I'm assuming I'm replacing a torque converter.

That being said, any advice on replacing the torque converter? I've never done it but read up and it seems straight forward.

Anything beyond the converter I should replace? Some mention putting a shift kit in.

I have a new trans filter and gasket so I'll wait to install till this is done.

 

I tested at the voltage at two pin connection, ran the truck to 30 mph got 2.8 possibly 3.0 volts but nothing higher than that.

Didn’t get a chance to dig much further.

Was going to do a RABS HZ test but the multimeter I have at home doesn’t have HZ testing ability. I got two at work that do so I’ll grab those this week

Only thing I can add is that when I drive beyond about 50, there is a little play in the speedo. Not a ton. But it’s not steady. Maybe 1-2 mph sway. Not sure that’s a concern or not.

Still leaning toward torque converter?

 

Been pretty busy, haven't had time to work on the truck.

So all electrical checked out.

One of two last things I didn't try:
1. Inspect torque converter for bluing
2. Check fluid further.

I went with fluid tonight. I checked it once before and I thought it was good enough. I read up more on how to properly check the fluid and I found the fluid to be a little low. On my dip stick I have two holes and then the hash mark is above those. The dipstick says do not add if within the hash marks. When I first checked, it was close to the top hole but not in the hash at all. I added what I'm estimating about 300ML to it and got it to the hash marks, about mid way.

Drove the truck after and hard to say it's fixed but it does shift better. I wouldn't think 300ML would make a difference but maybe it does? Anyone can chime in on that, that would be great!

Going to drive it some more and check again, see where it's at and also if the code pops again. If this solves it I'm going to drain the tranny and install a new filter and gasket and new fluid. Seems odd it would be low when I don't have any leaks from the tranny at all.

I'll look at the converter between now and this weekend.

 

Is your rear end a limited slip?
I have a new truck, thought it had a shift kit in it, it shifts really hard.
Now that I have owned it for a while, depending with how I drive it, it shifts normal some times and hard sometimes.

My problem turned out to be the clutches in the rear end of the limited slip.
New clutch packs, drive line is tight again.

 

You might want to check if a shift kit was installed in the transmission. That would make the shifts harder, if the kit is aggressive or sporty it will be very noticeable.

 

I decided I'm replacing the torque converter to see if that fixes it. Based on everything I've found its shot. Didn't see the bluing but it shudders and the system keeps popping the same code. From what I've read many have had good luck with just replacing that. I know the proper thing to do would be to replace the trans as well. I'm hoping to get some more miles out of this one if I can. Also, there isn't a shift kit installed.

That all said, need some advice...

1. Should I flush the transmission first?
2. OR Should I empty the fluid in the trans first?
3. OR install new TC and then flush the system?

@Mark Kovalsky can you chime in on this?

I do have a new TC and trans filter with gasket. I also have 24 quarts of Mercon V, enough to flush the system and fill.

Any other advice is appreciated. Especially when pulling the trans and re installing. I have read up on how to do the TC removal and install.

 

Dupliucate. Ignore.

 

No.Empty the pan. Do it when dropping the trans.Since you've replaced the torque converter and emptied the pan there is nothing to gain by flushing the trans.If the new gasket is cork, throw it away. The stock rubber gasket is reusable many, many times.
Change the torque converter hub seal and bushing. There is an aftermarket seal available that is made from a material called Viton. It is FAR superior to the stock seal.
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I haven't replaced the TC yet. I have the replacement TC and I haven't torn the truck apart yet. Plan is to do that this weekend.

Alright, I'll dump the fluid when I pull the trans.

New gasket is a Hastings one and it's rubber.

I will make sure to replace the hub seal and bushing. Was weary of doing that as I've never done that before but I'll figure it out and find it from that manufacture.

Thank you @Mark Kovalsky for all the advice!

 

Didn't have much time in the last month but started pulling the truck apart last week. It's also about -6 out and maybe 20 degrees in the shop so things aren't moving the fastest. And I've never pulled a transmission. After I did it, I think I had 8-10 hours into it. Had trouble with one of the cooling lines and after I got everything unbolted, I couldn't find one last bell housing bolt. It was the one beside the frame rail on the passenger side. Got the transmission out and feel really good about how it game out.

I'm ready to start putting it back together. I know how to put the pump seal in but my issue is lubrication for installing the torque converter.

So I'll fill the TC with 1 quart of Mercon V. Then my plan was to put a light coat of Mercon on the inside and outside of the TC neck, as well as the pump seal.

Some say to grease these, some say to use transmission assembly lube. Unsure which. To me, it would make more sense to use ATF/Mercon.

And then the nose (not sue what you call it, the front of the TC that meets the flexplate), some say to put a light coat of white lithium grease on it? Should I do that?

I'm looking for clarification and if I need to lube anything else. I assume the neck of the TC inside and out, the front pump seal on the input shaft, should be enough. Do I need to grease anything? If so what and what kind of grease?

 

That won't hurt anything, but it doesn't help anything, either, And when you put the converter on the trans you will probably spill some of it. That is, if you have the trans standing up, which is the way I recommend installing the converter.

MERCON V, right?

MERCON V.

Yes.

Before installing the converter you want to put a good amount of assembly lube (NOT MERCON V!) on the seals on the input shaft, then push the seals down in their grooves. The lube will hold the seals down for a while so that you can slide the converter over the seals without cutting them.