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I have a 1990 F250. 7.5 gas, 4x4, E4OD is acting up:
The transmission is "false-neutraling" in Drive. The symptoms are a little more complex, though.
2 weeks ago:
On a cold startup, the trans slips if I shifted from park to reverse within a second after starting the engine. If I take my time before shifting out of park, reverse slips less, but still slips for a few seconds. If I was to sweep the shifter all the way to 1 and let that gear engage (it does so solidly) then shift to reverse, it does not slip and works as it should. If I shifted to D from park on a cold start, the trans feels like it is basically in neutral. If I were to sweep to 1, then shift to D, the gear would engage more solidly. After warming everything up, the trans would work fine, except for a rare intermittent false-neutral while cruising: where the engine would rev up for about a second then thunk back into gear.
Currently:
I read online that the MLPS could cause false-neutral, and I also had no signal going to my reverse lights, so I thought I was correct in diagnosing a bad MLPS. Well, now I have the new MLPS in place and the trans is in neutral at any point the shifter is put into the D position. 1, 2, and R still seem to work the way they used to. I was careful to adjust the neutral marks on the sensor when I installed it. When I was working the shift arm (disconnected from the lever) back and forth to align the sensor, it feels like the internal detent is not fully engaging in P. A week before changing the MLPS I changed the fluid and filter as a pre-diagnosis step. The old fluid was exactly what you would expect a healthy, higher-mileage transmission to look like: not burned, still red, but darker. Unfortunately, I do not have enough experience with this transmission to be able to knowledgeably inspect the internals when swapping the filter.
Any tips for my next diagnostic steps? I've rebuilt my share of manual transmissions, transfer cases, and differentials, but I am pretty green with automatics.
As you have discovered the MLPS cannot cause this failure.
To inspect the internals you need to take the trans out and tear it down. You can't do it just by taking off the pan and the filter. I suspect that's what you need to do, tear it down. I think it's done.
As you have discovered the MLPS cannot cause this failure.
To inspect the internals you need to take the trans out and tear it down. You can't do it just by taking off the pan and the filter. I suspect that's what you need to do, tear it down. I think it's done.
Thanks for the reply.
What explanation is likely to cause the trans to engage 1st when the lever is in the 1 position, but not engage 1st in the D position? What parts in the transmission differentiate in these two shifter settings?
edit: The ATSG manual troubleshooting guide says the following (paraphrased) for no drive in D range:
1. low fluid
2. low pressure
3. bent/broken/mis-adjusted linkage
4. improper valve function.
5...
Does this mean I could potentially diagnose this without removing the transmission? I need an expert to give me a couple things I can check before I remove the transmission.
Last edited by TomatoJuice; Aug 25, 2023 at 09:19 AM.
Hey, thanks again for the feedback everyone. After a long wait, I was able to order a trans overhaul kit, I used the Transmission Bench Deluxe Super Kit for the E4OD/4R100 and a Trans-Go tugger shift kit. the Transmission Bench kit had all new friction parts, new seals, and a Superior Kit that required me to do some changes to the pump body. I followed the transmission bench step-by-step overhaul videos. I only found one part that was bad: the rear roller inner race. I cleaned everything and had a couple phone conversations with the guy in the Transmission Bench videos and I felt pretty confident and optimistic that the trans would be good to go. I took my time and tried to make sure I was double checking every step.
Same problems. The transmission is now engaging super firm in M1, M2, and R. Drive seems to give a blip of engagement before acting like it is in neutral. Not slipping while partially engaged, no noise. I drove for a half mile seeing if it would shift into drive if I was above 20 miles an hour, and no-go. I pulled the accumulator valve body and the main valve body and removed all the valves and double checked that everything was clean and moving freely. What do I do to diagnose this transmission issue now?
it looks like in 1st the low/reverse one way clutch is holding, and in M1 the low/reverse clutch helps out.
min 2nd the intermediate clutch is holding, and in M2 the intermediate band helps out.
it looks like in 1st the low/reverse one way clutch is holding, and in M1 the low/reverse clutch helps out.
min 2nd the intermediate clutch is holding, and in M2 the intermediate band helps out.
couls these two sprags have failed?
I used the same quick reference that you posted. I got confused becasue I was unsure which clutches effectively eliminate which sprags from the equation. Also, according to that chart, if i try to shift into drive from M2 at a speed appropriate for 3rd to engage, I would have expected engagement (assuming a bad sprag was the issue, a gear that allows the bad sprag to coast should work). Before the rebuild, my trans was going neutral at any forward gear and re-engaging with a bang.. as well as being sluggish to engage reverse from park.
I replaced the low/reverse inner race and when talking with the part vendor, he said that if I have a fully metal-caged L/R sprag and the rollers do not look damaged, it is probably better than a new replacement with a plastic cage, even with the inner race grooving that I found. A new overdrive sprag was included in the kit and I used the new one. I checked the sprags by hand that they engage in the correct direction and double checked everything as I assembled the transmission mechanicals.
The only thing I thought could cause this behavior could be a valve that was not operating or a clogged passage in one of the valve bodies. Since I could get the main valve body down without pulling the trans, I did exactly that. I removed all the valves and re-cleaned everything. I didn't get any big debris out, but I was able to identify a couple of spots I missed on the earlier cleaning that had some residue. I blasted everything with lots of brake cleaner and shop air. I don't know exactly what changed, because I didn't discover anything that would clog the valves or hydraulic passages, but I am now driving the truck and it shifts amazing. I need to tow a car hauler around next week, so I guess I'll find out how that shift kit works soon enough.
Was I correct about the hydraulic issue being cuplrit? I don't know. I was just typing out my thought process. I am not experienced enough to know if everything just started working by happy accident or because I actually solved a problem.
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