Transmission Failure

[tomj76]

I have a '96, 3.8L Windstar.

My rebuild transmission does the following:

If driven with selector in Drive, it will either drop out completely (neutral) when shifting to 3rd, or sometimes it drops down to 1st gear instead of shifting to third.

If Neutral is selected while moving down a hill, shifting to Drive will cause it to shift down to a low gear (2nd??). If the hill is steep enough to get your speed up to 30-40 where 3rd or 4th would normally be selected, it shifts hard down to 2nd.

If you drive in 2nd, then it runs fine up to second gear.

Code P0743 is given, "4th Gear Ratio incorrect", which indicates that computer expects the wheels turn slower for a given engine RPM.

Service Manual points to one of the shift solenoids, or "a mechanical/hydraulic" problem.

Sometimes the vehicle runs fine, but not usually.

[mark_gober]

I've never seen this problem, but the shift solenoids are pretty easy to replace. They are located on the drivers side, accessible from the wheel well.

The tranny mount goes right in front of the panel that they are behind, so it needs to be removed (use a jack to hold the engine level). Then, just remove the cover (it's multiple bolts, but most are easy to get to). Then you'll see 3 shift solenoids. I bought mine at RockAuto.com for about $15 each. To remove them, there is an electrical connector to you pull off and then a spring tab that locks it into place. Just depress that spring lock, rotate the solenoid 90 degrees and pull. The new ones just insert into the same hole and rotate the other direction. They will lock into place when they are in the right place.

Then just reassemble and test it. Hopefully thats your problem. If it isn't that, I'd suspect your Transmission Range Switch. It tells your transmission what gear you've selected. It's right on top of the transmission, connected to the gear linkage and they do fail fairly often.

Good luck.

[tomj76]

Thanks for your reply. The inner workings of the transmission is one of the big unknowns of the DIY universe. The Ford service manual is not as much help as I'd expect on this matter. The addition of the electronic PCM in this case seems to confuse the issue.

I have a few additional points of information that may go further to "point" to the ulitmate cause.

First, this is a used & rebuilt transmission in the vehicle, not the original. The original case broke when the differential failed during an interstate trip several years ago. The new transmission isn't an "exact fit" to the original, but it was good enough that my rebuilder (different than who installed the used replacment) felt that it could be rebuilt.

Before this first transmission failed, the van had a history of "shuddering" while cruising on highways. I eventually learned that this was due to "chattering" of the torque converter clutch. Now, when the transmission was rebuilt this chattering stopped for a short period of time (a month or so), then returned. The rebuilder looked at it several times, would "fix it", and it would work from anythingn to a day to a week before returning to the same behavior. His failure to diagnoise and fix this problem was not due to lack of effort on his part, as he even paid for a Ford technician to look at it and even completely rebuilt it a second time. Yet the problem still continued up to the time of this latest problem.

I took the vehicle to his shop for his estimation of repair of the shifting problem. He claimed that it needed to rebuilt again, saying that the problem was not electronic in nature, but possibly due to failure of the sprag.

I suggested to him that in light of the TCC chatter issue, is it possible that the transmission control circuits in the PCM are somehow faulty, but he didn't believe this was the cause.

I took the transmission to my Ford dealer service center for diagnosis of the chatter, but they said "replace it with a factory rebuilt trnsmission from Ford" and that they couldn't diagnosis mine since the parts used were not OEM. Although this seems a little severe, the third party rebuilder did find a number of "incorrect" parts at the time of the second pro-bono rebuild they did.

During a few trips the PCM has reported an issue with the transmission temperature sensor circuit. But this has been intermittent.

At this point, I've thought that a factory rebuilt transmission is a better choice than one rebuilt by a third party because I could get the chatter addressed under their workmanship warrenty.

Of course, if I choose to repair it myself, the solenoids can be replaced as you described.

The service manual is more than a little confusing on the diagnostic information for the transmission. However, it looks like a failed SS2 that is "always on" will produce the shift patterns that I experience. I'm not sure what could cause the soleoid to fail in the "ON" position. Can the valve stick? I suppose the PCM could fail in the "ON" state.

[trannyman52]

There is problems with this transmission that need to be addressed,,2 piece pistons Must be replaced,,converter replacement is a must,,,pumpshaft should be looked at,,,would not trust any of the electronics that are "good used".......not that tough to rebuild...but when done,,,it's a crap shoot it will work good!!!

[tomj76]

When "Drive" is selected, the transmission never drops into neutral when attempting to shift into third. If "2" is selected, it will shift from first to second and stay there. When I drive it "cold" in the morning (in "Drive") it will shift into third once < 1 mile, and afterwards always drop down into second gear.

I've driven it on short trips like this (< 1 mile) several times now. After the trips I have let it cool off for several hours and drove it again. It doesn't even give one good operation into third gear.

I removed the transmission electrical connector, inspected, and cleaned it. The pins look OK although several showed strong signs of corrosion. The dielectric grease was green (copper oxide) around these pins. After I cleaned all the pins, I took it for a test drive (late in the evening) and found that it did not shift to third.

Since the corrosion could be interrupting the electrical flow to the soloids, my next step is to check continuity of each pin in the transmission, and each wire through the connector, then check the voltage signal on each wire under operation.

[12Ounce]

I have little faith in most transmission shops. This has come after a few good ...but more bad experiences. Like has been said ... "its a crap shoot", and the player almost never wins!

But I have, twice now , used across-the-counter Ford reman transmissions that I installed myself. Both have 100k miles plus on them (each) ... and I expect many more miles on each one.