Hi Everyone -

My disclaimer in advance is that there is zero mechanical skill behind this poster - but am always the thinker and love this forum, which has helped solve many a mystery with my old truck, which I adore. Have dodged many expensive bullets just by reading all of the advice you offer.

I am hoping a mystery I have had for a long time with my 1993 F250 XLT (7.5L and e4od transmission) may have finally been given a new clue with what happened two days ago.

Have been having a "shudder" for quite some time around 50mph, have had hard shifts for 30K miles that, for 30K miles, have always gone in and out...not consistent. Won't go into the "whys" here...too long a story...regarding looking outside of the box (speed sensor, vacuum lines)...truck tows the rv like a champ, tranny fluid looks good, etc. Did not feel hard shift was tranny...possibly a gremlin, etc.

Anyway - was heading on a road trip two days ago and when leaving home (the rv), the door chime would not stop! If the key was NOT in the ignition, it would stop chiming when you close the door. BUT, with the key in, it chimed going down the road incessantly. Had an important family gathering, couldn't stand the noise, so had to do something.

So I pulled fuse #8.

Headed out on the road and it was like there was no transmission at all - no power, scary slipping....a true nightmare (remember, not mechanically inclined, so this felt really bad).

Having to get to my destination, I disconnected the chime, which was a relief to my ears, and put fuse #8 back in and, not kidding, the truck never handled so beautifully. Shudder 100% gone after months of this symptom. Felt power like I had never felt. The hard shift was gone. It was truly the best 100 mile drive I've had.

Coming back the 100 miles today, the hard shift did resume. Then, when almost home, there was a "gentle" shudder but nothing like I'd been feeling.

So I feel like I am finding some clues about this mystery. But I lack the mechanical knowledge to understand WHY.

Is the speedo memory on fuse #8 the issue? Why did unplugging and plugging back in make the hard shift AND shudder stop? More importantly, any suggestions where to go from here? I am in an rv with my dad in an assisted living facility...staying in the area until the better weather so I can go back home to Montana.

Know no mechanics at all - in an unfamiliar place.

Can you please give some advice?

And, of course, I am certain if I plugged the chime back into the harness, the door chime would incessantly ring again...so this is part of some problem, if you don't mind adding that into your theories! I don't like the chime, but I don't like having to keep it unplugged and not knowing why, either.

Thanks so much for your time...really appreciate your help.......Robin

 

The #8 fuse powers the speedometer. The transmission computer gets its speed signal from the speedometer. Not speedometer = incorrect shifting!

 

Thanks Lead Head....kinda figured....but having a hard time seeing the big picture.

If the chime hadn't coincidentally started going crazy out of the blue, I wouldn't have pulled the fuse. By pulling the fuse and THEN putting it BACK IN the shudder and hard shifts disappeared?

Is the chime going crazy a clue that there is something wrong in that #8 fuse area (is the gremlin hiding there somewhere?) which has been causing my much longer duration symptoms of shudder and hard shifts? If the chime never went wacky a few days ago, I wouldn't have ever known that pulling fuse 8 and putting back in would resolve these tranny mysteries.

 

I doubt the chime is the issue, and I'm not sure why the shuddering disappeared either. Is your speedometer erratic - does it sometimes jump around?

 

Speedometer is fine....

The only reason I mention the chime is that it part of fuse #8 too (when fuse was pulled, the chiming stopped) - part of the bigger picture - that's why I pulled it first when it wouldn't stop chiming with key in the ignition. I don't think the chime is the problem, but I do think it is a symptom of the mystery I've been trying to solve.

 

The reason I ask if the speedometer was erratic, because it's a very common problem with these trucks. When they get erratic, it's not just the needle jumping around - the speedometer is sending faulty speed information to the computer.

The EEC-IV computer in your truck is prone capacitor failure, which can cause erratic behavior and shifting. There are very few sensors the computer reads on your truck. There is a Fuel-Injection-Pump-Lever (FIPL) position sensor on the injection pump, and a vehicle speed sensor on the rear differential, and that's about it, really.

Ford actually released a TSB way back advising to check and replace the FIPL every 50,000 miles.

Also keep in mind the E4OD had several mechanical issues that weren't resolved until the 95+ model years.

 

Thanks for clarifying -

So if the speedometer were the issue, could I have had tranny issues "instantly cured" (temporarily - drove perfect for over 100 miles) because the speedo memory is on fuse #8? Does it "reset" so to speak when pulled and replaced? I just feel like the fuse has to be the clue to help narrow this down.

Did replace the speed sensor a few years ago (no change in hard shift), but not sure if the mechanic used original Ford parts. Worth trying to replace again, given the symptoms?

The reason I am stuck on the electrical gremlin theory is that until I had a new stereo installed last year, the old one would come on/off randomly. Also, the dome light AND chime only come on if the driver door is opened, not passenger. And again, speedometer memory (and tranny symptoms which resolved)....all of these are on fuse #8??

 

You're thinking diesel, and this is a gas engine truck. So there is no FIPL, instead there is a throttle position sensor (TPS) and many other sensors. Any one of them can cause this problem.

The first thing to do is to read the codes. You can buy a $30 OBDI tester for Ford vehicles at most parts stores, or you can do it with a paper clip or piece of wire. Ford ? OBD Trouble Codes

once again that was on the diesels. The TPS lasts much longer on the gas engine trucks.

Very true. But none of those mechanical issues resolve themselves when the computer's memory is cleared by removing a fuse.

The speedo memory is non-volitile. That means it can't be cleared. What WAS cleared was the EEC-IV computer's memory. That's the computer that runs the engine and transmission. I think there was codes stored in the computer, and many of those codes will cause harsh shifts. That's the computer's way of protecting the transmission from further damage when it detects certain problems. Get the codes read, as stated above.

Only if the codes indicate a problem with the speed sensor.

 

Thank you, Mark - will pursue the great advice you shared.

If you don't mind my asking, just a few more "minor" questions:

Do you agree then with Lead Head that the incessant door chime while driving really had nothing to do with anything...just a coincidence in all of this? Unplugged for now but would like to know what happened there.

Is pulling and replacing fuse 8 similar to disconnecting/reconnecting the battery? When I would reset the battery, the hard shift would stop for quite some time. However, it had no impact on the shudder symptom. But when fuse 8 was pulled, it temporarily relieved BOTH symptoms.

Thanks for your patience and assistance.........

 

Mark (and Lead Head and anyone) -

I will read codes and follow up - but here is something that I "think" matters, which should be mentioned.

SOMETIMES the hard shift just goes away - like the computer is cleared on its own!

Wouldn't this be important with my theory that there is something "shaky" in the fuse 8 area, given the related systems it plays a role in and the problems I've had with those systems? Again, think door chime, overhead light, last radio would go in/out, etc....

Battery, cables and alternator loose can be ruled out - got new everything in that area from a mechanic I trust, back home in Montana. Because hard shifts would come and go, that was the first place I looked...like the battery was resetting itself.

But the things fuse 8 covers, I have some problems with. Is it "possible" that something on that circuit (right terminology, I hope?) is going in/out, loose, etc? Meaning that is why it clears the hard shift randomly? The hard shift going away happens quite often and have never been able to figure it out.

I know I read a thread when researching before posting where someone mentioned fuse 8 was loose (not in my case, of course) and when pushed in, tranny issue resolved.

Intermittent, in my limited knowledge, often seems to have an electrical problem component?

 

I did not know this. I just bought a 1996 f150 as a future project. Was going to swap in a E4OD from a 1993 parts truck I have since it only has 150K on it vs the one in it with 212K. Was the changes significant enough to where I should just keep the 96 tranny with more miles? - I appreciate it.

 

Whoops sorry, I originally read your post as having the 7.3L (which would be the diesel). I see now that you have the 460.

There are several sensors used for shifting - engine speed (PIP in the distributor), brake switch (for converter unlock), throttle position (TPS), vehicle speed (rear differential) and there is even some altitude compensation.

Pulling the #8 fuse will not reset anything. Hard shifting normally indicates limp-mode, in which case your O/D light will generally start blinking and/or the check engine light would be on.

I suspect you may have a wiring problem, or your computer may be failing if the behavior is erratic and no codes get set. I'd check your computer for leaking capacitors, which is becoming increasingly common on these trucks.

 

All that means is that whatever is wrong sometimes works correctly. If the computer doesn't detect the error it will operate normally until the problem occurs again. This doesn't tell me anything is wrong in the fuse 8 area.

Batteries don't reset themselves. There is nothing in a battery to reset. Either it has voltage or it's dead.

Yes, it's possible. Likely? Who knows, without knowing the codes.

Yes, I agree with that.

 

Thanks to both of you....

Lead Head - so you know, the O/D light has never blinked (the light does work), the check engine light has never come on. Also, the brake light switch and speed sensor was replaced while chasing this problem down.

Mark - will get on those codes. One clarification, I didn't mean batteries reset themselves. I meant when the hard shift comes, you can make it disappear for an extended period by disconnecting the battery, then reconnecting.

Was so certain it was the speed sensor way back when, due to the issue where RABS brakes locked up and would only unlock by pulling the RABS fuse (can't remember right now which one). Due to the speed sensor and RABS being the same sensor, if I understand correctly, I was certain I had it figured out.

 

I think the problem with the chime is a bad (broken) ignition key cylinder. I had the same chime problem with my 1993 F250 until I replace the ignition key cylinder, not the switch.

I also had to replace the MLPS and my computer in it to solve the hard shifts. I do not know if it was the computer or the MLPS causing the hard shifts but both were bad when I bough the F250. I and replaced them both at the same time.