Hi all, new to the forum and hoping to find a solution to a big issue I've been having for 2+ years now. I apologize for the long post but it contains most of all my trouble, and all symptoms I can think of.

So I have a 1992 f150 302 e4od 4x4, and had the transmission completely rebuilt. I have always had this 1-2 hard shift (it can be a very light clunk to a solid "felt like someone rear ended my truck") since I bought the truck. Originally the transmission was full of metal in the pan, the reason we first suspected a big problem. The transmission has been completely rebuilt, additionally with a second rebuilt torque converter put in, 2 new valve bodies, 2 new pressure modulator valves, and the sort. I just had it in the transmission shop again (two days ago) with everything mechanically checking out. Up to this date as well, I have changed the VSS, MLPS, and TPS. All other gears shift perfectly, except 1-2. There are a few other symptoms with the transmission and truck, which involves an occasional ABS light when around the 40-55 mph range. It comes and goes every once in a while, usually when I'm just barely touching the gas, almost completely off. Additionally, sometimes the truck when almost off the gas, barely touching, will cause a type of surge in the rpm, as though it kinda changes gear but then doesn't (this happens sometimes, but not always). It will keep doing this surge until u let off completely, or give it more gas. The surge feels like a light push, leading me to conclude some type of shift is occurring.

One strange incident I experienced when I went to the transmission shop to drop off my truck last week was when I went to drive around the block to show the mechanic the hard shift, the truck decided to shift perfectly. I can't explain it but we went around the place for a mile or so, and it did almost 15-20 shifts perfectly, until just before we got back, it started to go in a little hard, but nothing comparable to what I've had in the past. The same morning as I was driving to the shop, it had hard shifts from 1-2.

The transmission shop kinda led to what may be causing the problem, which they pointed out that my alternator was sometimes kicking out 17 Volts. I tested it myself with a voltmeter and it seemed to be running in the right 14.6V range, but I changed the voltage regulator regardless. Problem didn't fix. One other thing he mentioned was some spikes in the signal coming from the TPS. I'm not sure exactly what that's implying, but we tested it ourselves with a voltmeter and it had a good steady increase in voltage when throttle was applied. The only concern I had over my dad was the closed throttle on the TPS was .78V, and WOT was 4.36V. I'm thinking those values are low, but I'm unsure of the effects that could have to the vehicle.

At this point, I am extremely stumped with what the issue could be. The only parts I can think may be causing problems could be VSS (indicated because of the ABS light occurring sometimes), but this sensor was changed completely with a brand new one. The TPS could be an issue again with some of the indications given, but with all the testing I have done, I have my doubts. The ECM is the last thing I can think of that has not been changed that could be causing these problems. I know its unlikely, but at this point I can't come up with much else.

What really confuses me again, is how the truck went for months running with a hard 1-2 shift to running perfect the second I show the mechanic the hard shift, then back to running like crap when I get the truck back later on.

For anyone able to help, give me any ideas you can think of, and I will try to respond my best to them. Again, thank you in advance.

 

I forgot to mention, but the code reader does sometimes pull a code 225, knock sensor fault, but other times it will come as 111. The other thing is, my code reader likes to tell me my truck is a 6 cylinder, but its an 8 cylinder. It has done the 6 cylinder reading since we got it. When I got the motor all fixed up and running correctly, it would sometimes throw a 8 cylinder and then a 6 cylinder if I tested just after it. It did that for a while, kinda changing, and then went back to only reading as a 6 cylinder.

 

Changed the VSS back to the original one we had. It tested good so we replaced it, with no change. We also took the TPS out and adjusted it to be at .9 volts at closed and 4.48 volts at WOT. We also found the battery terminal for ground was corroded on some sides, so we striped the wire back to where it looked good, and put a new terminal on. My only conclusion now for some of its erratic behavior is the computer or the connector to the computer.

 

Erratic codes is an early sign of computer trouble. Pull the computer and inspect for leaking capacitors.

Does your speedometer work smoothly, or does the needle shake a bit?

 

Thanks for the reply. It will be a few days before I could pull the computer, since there is a snow storm that just started this morning. The speedometer works smoothly, so I don't think there is an issue there.

 

Okay, so the code reader seems to have a hard time reading the signals it gets, so it is receiving 4 signals (but keeps saying its a 6 cylinder). We did that on the new computer we just replaced, and I keep getting the 225 knock sensor fault code. It is fairly consistent, but not always (KOER). KOEO has no codes at all. The old computer had a capacitor with a leg completely burnt off.

I will have to give it a few more miles for the computer to settle, but my initial test drive still had a harsh engagement into drive, and the 1-2 shift wasn't as hard, but as RPM's got higher, so did the severity. At this point, if the truck continues what it's doing, I will probably start checking the grounds and wiring. As well as for engagements, reverse to drive can be severe.

 

The computer didn't help with any shifting issues. The only correlation I have is since I changed the voltage regulator, the shift patterns changed. Any ideas what could be wrong electrically?

 

Could possibly be a high resistance in the EPC circuit to the transmission.

 

So me and my dad took a look at the rear differential and the drive line. I put the truck in neutral and let him turn the drive line, which freely moved an inch (can't remember exactly but about 25-40 degrees of rotation). The drive line going into the transfer case also moved up and down slightly (very little) when being pulled and pushed on. I'm going to assume based on all of the symptoms, the back differential is in really bad shape, and possibly something in the transfer case. It comes as no surprise since my front differential (for 4x4) is probably toast as well. 4x4 actually makes my truck do a hopping motion when the tires gain any amount of traction. If anyone has an idea of ways to test the back differential for excessive wear (to be sure this is the problem), let me know, or if this movement in the drive line (in neutral) is a solid indication of a major problem. Thanks in advance.

 

I got a 1992 F250 460 with the e4od and since I bought it it shifted hard 1-2 and O/d problems. I paid $3200 for a complete rebuild. Still got code 62 and hard shifting / no o/d. I was stumped. Finally after reading and reading on these forums I narrowed it down to a few select systems. When I got my truck back from the trans shop, it shifted like a pos and I was pissed. I banged the dash above the speedometer / PSOM and bam, problem fixed. It also fixed my Rear ABS ligh - meaning when abs light comes on I bang the dash and it goes offt. My problem was electrical not mechanical. The PSOM is a weak link that intermittently gives problems to the trans. I'm not joking try simply tapping/banging on the top of your dash while driving / when it feels like 1st gear is going to max line pressure and see what happens.

 

Its valid to think its the PSOM, but the ABS light comes on when the rpm gets low around 50-60. That's engine vacuum from what I can deduce (since originally a lot of the emissions was stripped, and later put back). My front end I know is damaged in the differential, but the rear end is still unknown to me. Banging on the dash doesn't help. Absolutely no codes are thrown, except a rare 225 (knock sensor fault), but that should not effect the transmission.

*Just to reiterate for anyone else, the 1-2 shift is very hard, usually under load. If you go down a hill, the shifts can be not felt or very light.

*Park to drive will go in hard, and drive to reverse will feel like the truck dropped in height and moved backward (as though it was sliding backward).

*If you let off the gas going up a hill, the truck will shudder (usually in 2nd, 3rd, and OD). The truck will shudder without changing gears. Sometimes going on the highway up a hill after letting off the gas completely (say to slow down) and then pushing on the gas, the truck will shudder a little bit when power is reapplied.

*Around 30-40 mph, under extremely light throttle (flat ground usually and hard to reproduce), the truck will start to shake back and forth and the rpm will surge up and down about 200 rpm and will continue to do this until throttle is reapplied or completely let off. If throttle is reapplied under these conditions, the truck will shudder a little bit and go back to normal. If let off, the surging will stop, but reapplying throttle will cause a small shudder.

*The transmission shop stated that the alternator or battery was sometimes outputting 17 volts, and that there was a signal spike in the TPS (not sure when or under what conditions the spike occurred). The battery read within spec (from my own test), but changing the voltage regulator seemed to of made a little difference in the shift pattern, and overall electrical system. They stated there could be a bad ground, but I'm not sure where. TPS from my own testing read within spec.

*After pulling the computer, 1 capacitor was completely burnt at the leg and severed. Not sure if this will have relevance, but a new computer was put in to replace it. The new computer had no effect on the current issue.

These symptoms match many instances on the forums, but most people always have an error code which helps to track the issue, which I don't have. Any suggestions will help, but I'm trying to not throw parts at this anymore. If anyone has a clue of what I can directly test with a voltmeter or just generic tests of components, I'm all ears.

 

So I tried something new, and I pulled the VSS and decided to drive without it for about a mile. The truck ran almost perfectly, with some very minor clunks, and no hard 1-2 shift. The truck did act a little funny with the shifts, but it would be expected without the VSS. I know the VSS is good because I've had a brand new one put in and the old one in a few times with no changes.

Is it reasonable to assume that since the VSS is not providing information to the PSOM and therefore no information to the computer, that the PSOM is the likely culprit?

 

At this point, it looks like the PSOM is not operating properly. There are capacitors on the PSOM PCB that will leak and damage the 8000 pulse per mile output circuit. Without a good clean square wave from that output, the ECU will cause hard shifts with the E4OD. All the while the ODO and speedo will work correctly.

This is a common problem as these trucks are aging.

 

So we took the PSOM out and it seemed to be a newer board than what should be on it (a F6 version, rather than an F2). There didn't seem to be any leaking capacitors, etc. The board looks to be in good shape, but internally, I can't say. We tried sticking a new PSOM in and it was completely dead. Didn't even click on or show millage. That board had a burnt circuit which I had to jump with a wire but was still dead (the burnt circuit was under the round black capacitor). So we took it out and put the old one back in for no change. The guy who sold us the board made right and sent us a new one (used) but in better condition. Hopefully the 'new new' one works and cures the problem, otherwise I'm back at diagnosing.

 

I wonder how many miles your truck actually has on it then, if it had a newer speedo in it?