I have a 92 F250,351w,with an E40D tranny. I recently rebuilt the tranny myself using only ford parts.It worked great for a little while and suddenly it will not shift into overdrive. I replaced the MLP sensor with the upgrade kit which has new connectors also. The only code I have is 512. No flashing overdrive indicator.All other gears work great but no overdrive. Could this be the soleniods?

 

I think you've got them think'n,did the rebuild go easy and did you have to buy trans tools .I would like to give it a go myself but wonder about the skill level.S.L

 

It wasn't real easy. Used alot of space,made sure everything stayed clean and watched very closely what I was doing.I made myself alot of notes as to where the ***** came out of and and the position of the parts as I disassembled it.I also had the local Ford dealer fax me an exploded view.

 

Did you need any special tools or fixtures to compress springs or clutch-packs?

 

No sir I didn't.I am a mechanic of sorts by trade( not on autos)and most of the tools I already have.The overdrive drum was a little tricky but not really that bad.The worst part is that there are alot of small parts. atcdg.com -tech section has some decent info. If you have the time and are careful it can be done.I only wish that I could get an idea of why my OD won't work.

 

Well, theoretically, the problem would fall into one of two categories:

1. The transmission is not being signalled to shift into OD
2. The signal the transmission is receiving to shift into OD is not being converted into a shift into OD.

I'm more used to diagnosing the hydraulic systems for signalling shifts in transmissions, but I gather that the OD shift signal is electronic, and is triggered by the main powertrain ECM.

Since you didn't change anything in the ECM, then I would focus on the system for shifting into OD. I'm gathering that it's a solenoid which either is not getting its signal, which is getting its signal and not shifting into OD, or which is attempting to shift into OD but which is being blocked by a mechanical hangup.

I've got the manual at home and can study that OD shift circuit to see what it might be.

It's also good news about there not being any unique tools for doing this transmission. My last transmission was a TF727, which can be done with ordinary tools and some ingenuity.

 

I would appreciate any suggestions you could come up with!I drove the truck into town today and it shifted into OD but not every time and also now it stays in 1st gear sometimes until about 3000 rmp. I spoke to a transmission shop today and they told me how the adjust the MLP sensor without any special tool.And said that the TPS or the speed sensor would explain the problems.So I adjusted the MLP,replaced the TPS and the speed sensor---no change.

 

OK, I see a few possibilities at work here.

First, a possible assembly issue. It looks like the overdrive clutches are installed using selective snap-rings, and that the pressure-plate and snap-rings have to be installed in a certain orientation. This is all on page 56-57 of the ATSG manual. You might have problems if you didn't do that part right.

Then there is the diagnostic procedure for the "No 3-4 shift" condition in their troubleshooting pages. Here's some relevant possibilities (beyond "check fluid level" and such):

3. Check solenoid operation (S2 solenoid suspected)

4. Valve body bolts loose or tight

6. Inspect 3-4 shift valve (valve stuck, nicked or damaged; springs missing or tangled)

7. Inspect overdrive accumulator regulator valve (same as #6)

8. Inspect overdrive clutch assembly (clutch cylinder damaged/feedbolt loose or missing/sealant leaking/cylinder ball check assembly stuck or missing)

There are also procedures for checking clutch engagement using air-pressure rather than fluid-pressure on the valve body. Again, the ATSG manual has the procedures and the diagrams on pp. 9-10 of its E4OD manual. It's well worth the $17 I paid for the manual.

 

I drove up to Houston today and located a copy of the service manual.Tommorrow I,m going to pull the pan and check the valve body.
I shouldn't have gone thow,cuz now I'm the proud owner of a 88 F350---460 with manual tranny.