Ambulance tanny shifting problem

[pmwalter]

I know there are some smart folks here!
I have a 1991 Ford E350 Diesel ambulance (retired). it's now a camper. The tranny at completely random times decides to shift really late. The transmission will be in hight RPM before it shifts. This is for all four gears as well. We just replaced the entire tranny, but it is still there. Has anyone had this issue before? Any ideas?
Thanks.

ps. Once the van warmes up, it usually acts fine.

 

[pmwalter]

I should clarify. The tranny will shift late for a while after it has warmed up. Probably 10-20 minutes will go by before it acts normal. This happens in all sorts of different weather.

 

[punisher]

Refresh my memory, C6 or E4OD?

 

[pmwalter]

I knew there would be a hard question. Sorry punisher, I actually don't know. I meant to find out but never did. Are there big differences with them?

 

[Vstrom]

 

[Vstrom]

Does it have an OD cancel switch? If so it is an E4OD. If not it is probably an AOD. The C6 is a 3 speed.

 

[Gary Allan]

quote:

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We just replaced the entire tranny, but it is still there.

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Was this the one of the conditions on the old trans?

In a conventional (hydraulic) trans I would say whatever interprets throttle position is dysfunctional until warm (whatever valve is acted upon) .I'm not sure which year they abandoned the vac-mod on these trannies. For all I know ..they get output from the tps/map by that stage of devolution.


Have you attempted to shift manually during this event duration??

I would naturally recommend purchasing the FSM for this chassis. There would be a diagnostic go, no-go section for the trans.

 

[pmwalter]

Yes, it does have a OD cancel switch, and it is a 4 speed tranny. I have tried shifting the gears manually to no avail. Once the van is warm, it tends to go away. It may take 20 minutes or so before it drives normally.
This condition is what promted us to replace the entire tranny. Once it was rebuilt, the problem persisted. Ford dealership says they have no idea. That is why I have come to the pro's!

 

[Gary Allan]

No knowing the "normal" aspects of this engine trans combo ..at least at that "state of the art", are you sure this is not normal? In some Cummins/auto combos it has been reported that the OD won't engage ..sometimes for many many miles since some thermal threshold must be reached first. Admittedly they didn't report any higher shift points that were temperature dependant however. It appeared limited to the OD engaging ..and perhaps a lockup feature as well. Most ambulances are plugged into ambilicals that have everything prewarmed to allow rapid response without incurring undue wear.

How radical are these shift delays?

Since the condition is self correcting with warm up (which could easily take 20 minutes given the heavy duty intended use for this unit), one would reason that some trigger (signal, threshold, etc.) has been reached. This may be electronic in nature.

Again, I'm working blind without working knowledge of this engine/trans/year/duty combo.

There are shift kits that would probably eliminate this condition ..but you may find out, with further reasearch, that this is actually a feature that you may not want to defeat.

Please keep us updated on your struggle with this condition.

 

[pmwalter]

Ok, it's actually a 3 speed w/OD "E40D" tranny. I thought I was on to something with a vacuume modulator. Tranny is apparently electronically controlled. Diagnostic paper from AAMCO showed no codes. They could not find anything wrong with it, so they rebuilt the thing. Probably rebuilt a perfectly good tranny!
Any ideas of where to go from here? Could a computer be doing this, or is is strictly mechanical? Since it works after it warms up, it seems mechanical to me.
Hmmmmmm...

 

[punisher]

E4OD= ELECTRONIC 4 Speed Overdrive

No codes usually mean driving it around with a monitor hooked up to it to measure MLP and TP position etc and looking for an intermittent electrical glitch.

First thing I would do is pull the connector at the MLP sensor (electrical switch at the gear selector shaft on the trans) and examine it for any corrosion/water intrusion etc, ditto for the main connector on the trans. I have seen a fair amount of MLP sensors on E40Ds and 4R70Ws/AODEs cause intermittent problems due to water intrusion either at the connector or around the shaft. Verify the MLP is clocked/indexed/adjusted correctly while you are under there (hash marks on sensor body and shaft collar will line up in neutral).
The ideal way to do it would be to drive it with a monitor/recorder on it and get a snapshot of your inputs when the glitch occurs. This is one of those situations where the correct tools are a major timesaver.

MLP doesn't normally set a trouble code when it glitches.

 

[eljefino]

I'm leaning against it being computer controlled, except perhaps for a lockup torque convertor. I bet it's mechanical and there's some wierd widget that converts a vacuum/gas engine tranny to diesel operation. Even if it's just a different governor with different shift points, it'll be a rare part on a common transmission. I don't know ford automatics or if the gas version used vaccuum... Do you have a rod or cable from the injection pump that moves with the acellerator pedal that goes to the trans?

Having it stay out of overdrive for 20 minutes in what was an original ambulance installation would be unacceptable since it could increase response time to an emergency. I doubt it was set up that way.

 

[Ugly3]

The shift to OD is probably temperature controlled. It is in my Van. Have to get to almost full operating temp before it will go into OD.

 

[Gary Allan]

What he describes isn't intermittent. It's warm up related. That is, cold ..delayed shifts ..warm ..normal. Ambulances are typically linked to ambilicals that have the engine prewarmed (they all are in my town's ambulance outfit).

Cummins owners report a normal condition that their trannies won't go into OD until the thing goes about 15 miles.

That is, I imagine that if he idled it long enough before starting out ...it wouldn't shift funky. He may just have a lame CTS ..or trans temp sensor. They've had them for a while now. My simple 30rh (904 with a lockup converter) won't go into lockup until the trans reaches some preset temp.

 

[pmwalter]

I can't find the stupid coolant temp sensor. I think it's behind the air cond. compressor, but I can't get back there without taking it out. I can't believe how difficult it is to work on a Ford Econoline. Any tighter and I would have to send in my 16 month old daughter to get to certain parts!

Going to work on it again this weekend. We'll see how it goes.

 

[pmwalter]

Well, I've been playing with this ambulance a bit more. I've noticed now that the gears shift at certain speeds.

For example: 1st gear will be in high RPM until about 25-30MPH. Then 2nd gear will be in high RPM unitl 45MPH. It has been pretty consistent this way. I was able to force it into 2nd gear by keeping the shifter in 1st, then shifting it into 2nd. However, it will not do that for 2nd to 3rd.

Once I achieve those speeds, the tranny will work perfectly for the rest of the day. I'm still waiting to install a new coolant temp sensor. All I have to do is rip out the A/C compressor to get to it.

Another piece of the puzzle.

 

[TallPaul]

I have a 1990 E350 motorhome with the E4OD and gasoline engine and since I bought it in '01 it has always shifted beautifully (well, as beautifully as an automatic can shift), but as soon as I bought it I installed a Banks Transcommand module which firms up the shifts nicely when needed.

Check out this informative page on the E4OD. Call these folks. They know their Ford automatic trannies. Another of their E40D pages says:

quote:

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If you have recently purchased your vehicle, and are unsure if the behavior [seemingly weird shifting etc] is normal, please contact us and we will be happy to help you determine if you have a transmission problem, or if your transmission is operating as the factory intended.

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[ April 30, 2005, 11:46 PM: Message edited by: TallPaul ]

 

[pmwalter]

TallPaul, I noticed that the early models are not spoken well of. My tranny was rebuilt two years back. I wonder if they used the updated rebuild kits that the site mentioned.

By the way, what did the kit cost you? Some of the pages were down, so I couldn't tell. Thanks

Ahh, thanks for the update. I'll have to give them a call.

 

[TallPaul]

Yeah, the early models are not as good, but mine is a 1990 and I have had zero problems in the 77000 miles I put on it (52K to 77K). Had half the fluid changed to M1 when I got it and then last summer changed 14 of the total 16 quarts with M1 again.

I did not buy a Baumann kit as I was installing it myself. I believe theirs is a valve body kit. I bought an electronic kit from BanksPower.com for I believe around $250 or so. It took only an hour to install and works great. Shifts firm up more with more load.

But their site says the shift kit will not cure a shifting problem. Since yours was just rebuilt I would think you are OK, but should call them to describe what is happening and let them tell you if you are normal or not.

I do hope the shop that rebuilt yours used updated parts.

 

[pmwalter]

Just when you thought a thread was dead!

I recently did a coolant flush for this rig. Seems that the last coolant change was with standard old style green Super Tech antifreeze (not the new universal type). I flushed the system nine times (yes, nine times. I really had nothing to do that day) and refilled with Zerex G-05. This is also the first time in a long time that a "charged" antifreeze was added since it is a diesel.

To make a long story short, I haven't had the tranny problem since. The weather has changed just a little bit, so that may be a factor, however this once cronic problem has seemingly gone the wayside after a coolant flush.

Does anyone think that antifreeze could be a culprit in transmission problems?