CD4E transmission, how do you really feel?

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Old May 12, 2007 | 12:54 PM
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lrhogfan's Avatar
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CD4E transmission, how do you really feel?

Just thought I would throw this out there in case anyone had any strong feelings one way or the other? So, CD4E... good or bad??

 
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Old May 12, 2007 | 01:02 PM
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Stay on top of your fluid changes up and you'll be fine. If you don't, you'll likely be a "Grumpy Gus"........

Most people who have trouble with this unit are the type that get to 60,000 miles and then say, "You mean I was supposed to change the transmission fluid at 30,000 miles?!"
 
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Old May 12, 2007 | 01:29 PM
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Actually... there is two issues at risk here...

1. First generation Escapes had an incorrectly marked dipstick for the transmission. The factory dipstick said use Mercon V only. Dealers, mechanics, and DIYer's were throwing in Mercon V. The seals inside of the transmission require regular Mercon. So that had some issues. But that was corrected by replacing the dipstick. So some trannys were lost due to that. But that is not an issue now. So as a FYI don't put Mercon V in your tranny.

2. The manual stated transmission fluid changes at 150,000 miles. ddellwo is right, keeping on top of the fluid changes is a priority. But irregardless, you can still lose the tranny.

Even with that, all my tranny failures occured before 30,000 miles each.

Heres some good info:

by Larry Frash

When mainline demands on the pump increase, the pressure regulator valve starts choking off converter charge in an attempt to maintain as much mainline as it can.

Even though there aren't a wide variety of problems associated with the CD4E, the ones that do occur happen frequently. In this edition of Transmission Therapy we will cover problems such as uncontrollable line pressure, cracked forward drums and converter clutch slippage. Sometimes these problems stand alone; other times one problem can lead to one of the others.

Converter Clutch Slip

Codes 628, P0741 and P1741 all indicate the torque converter clutch is slipping. Not only are these codes plaguing the industry, they can be a pain to fix. In many cases, on pre-98 vehicles, updating the pump (Ford P/N F7RZ-7A103-AA) will correct the problem. The problem was the early pump didn't have enough support for the gasket (fig. 1), which allowed it to blow out.

Because the gasket blows out on the suction side of the pump, it greatly reduces pump volume. As with most other transmissions, low pump volume causes low converter charge and allows the converter clutch to slip. Even if the gasket is okay it can still leak air into the system, reducing pump efficiency. Always update the pump during rebuild, regardless of whether the converter clutch was slipping. The updated pump has more support in this area (fig. 2).

Very often the converter clutch will still slip, even after updating the pump. In this case, the valve body may be worn out and be in need of replacement.

Uncontrollable Line Pressure

Another cause for the converter clutch slip is excessively high line pressure. When mainline demands on the pump increase, the pressure regulator valve starts choking off converter charge in an attempt to maintain as much mainline as it can.

This leads us to the second common problem: uncontrollable line pressure. And we're not talking about a measly 300 PSI either. We're talking case breaking, valve body exploding, 400 psi-and-higher pressure!

The problem is that the mainline pressure regulator valve is wearing out the bore. If the bore is only slightly worn, you can enlarge the balance hole to 0.055" (fig. 4). But if the wear is excessive, the only answer is replacing the valve body. Remember, buying a used valve body is okay, but the mainline pressure regulator bore may be worn in it, too.

Cracked Forward Drums

The third problem--cracked forward drums--is probably more common than the first two combined. There are five types of drums available from Ford. Use the illustrations in figure five to identify which drum you need to order. The drums haven't been redesigned, but there may have been a problem with the production process rather than the design, because the new drums seem to be holding up, even though there are no noticeable changes.

It's also possible that excessive, uncontrollable pressure has caused the problem. It's not a bad idea to drill the mainline regulator balance hole as a rebuild procedure.

As you can see, most of the problems we've covered here are caused by high line pressure. This is a perfect example of a problem where you'd want to check line pressure before you remove the unit. You just might save yourself a little time.
 
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Old May 12, 2007 | 01:30 PM
  #4  
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CD4E Turbine Speed Sensor Headaches
by Mike Van Dyke

The latest design replacement CD4E turbine speed sensor (TSS) and its related problems have been the subject of many calls on the HelpLine recently. I remember one call specifically that really nailed down some of the problems related to the new design sensor. What helped was that the technician was really intent on finding the cause of this problem. The call went something like this: After getting the account number I asked him what he was working on.

"I have this ’96, 626 with a CD4E transaxle we overhauled about a week-and-a-half ago. It came in with a broken drum. We went through it and replaced the drum. The original valve body was worn in the pressure regulator bore area, so we installed a new valve body and solenoid block. We also installed a new MLPS, VSS, and a new TSS, which was a new design that looked different and came with a longer mounting bolt. We don’t like to reuse electrical parts because we’ve seen too many problems caused by old parts.

"Now, every few days this thing comes back with the same problem, harsh upshifts and the OD light is flashing. It usually has the same codes: P0742 (TCC performance), P0733 (third gear ratio error) or P0732 (second gear ratio error)."

I asked, "When you clear the codes, will they reset on a road test?"

"I’ve driven this car home, on parts runs, all the way to kingdom come and back again, and I can’t get the codes to set. But when I give it back to the customer, they’re back within two days with the same complaint."

It’s frustrating and difficult to diagnose problems when you can’t duplicate them. It doesn’t help that Mazdas with CD4Es are very reluctant to give a data stream. All you have are some DTCs and an impatient customer. I started thinking about why the codes would set with the customer, but not when the technician road tested the car. The conditions must be different somehow.

I asked, "Has the customer mentioned what the conditions were when the overdrive light started flashing? Was it when he was accelerating? At a cruise? What speed? Cold? Hot?" Trying to see if there was some way we could duplicate the conditions. "No, he didn’t say. Maybe what I’ll do is get a hold of the customer and see if he recalls the conditions of how the car was being driven."

The callback afterward indicated that some progress had been made: "The customer says there’s a long grade on the way to work everyday. Sometimes he gets stuck behind a slow-moving truck. When he pulls out into faster-moving traffic to pass the truck, that’s when the trouble starts."

That was the key… the condition. And with that the technician was able to duplicate the problem. But what was causing the problem? The codes indicated there was a slip in second gear, third gear, and at times even excessive converter clutch slip.

The upshifts were always consistent and positive. The technician didn’t detect any slip via a "seat of the pants" test. A pressure gauge indicated that line pressure was consistent with throttle opening when the codes set, ruling out insufficient line rise. A signal monitor indicated the transmission upshifted and down-shifted when commanded, and was always in the commanded gear.

At this point we suspected an input to the PCM was more than likely the culprit, and the one input used to calculate converter clutch slip and gear ratios is turbine speed. After deliberation, the technician decided to substitute another TSS he had taken off of a core unit.

Viola! No more problems! Now he could wind up the rubber band real tight on that little Mazda with no complaints from the PCM. There were many calls after that in which the technician was able to duplicate the problem with highway speed kickdowns, which made diagnosis much easier knowing what to look for.

Here are the latest observations on this hot topic:

The TSS is in a prime location to cause trouble. The Powertrain Control Module (PCM) calculates torque converter clutch slip by comparing engine RPM to turbine shaft RPM. The PCM also calculates gear ratios by comparing turbine shaft RPM to the vehicle speed sensor signal. The result is that a bad TSS signal can cause both TCC performance codes and gear ratio error codes.

A common complaint heard is the overdrive light starts flashing after a 4–3 heavy throttle kickdown at highway speeds, such as when overtaking another vehicle. Under these conditions, a third or second gear ratio error can set due to the new design sensor’s lower signal output voltage at high RPM.

The magnetic field of the new design sensor from Ford (P/N XS7Z-7M101-KA) is quite a bit weaker than the previous design (figure 1), and the sensor has a lower signal voltage output than the previous design (figure 2). Additionally, the signal voltage curve generally flattens out as turbine shaft RPM increases (figure 3).
 
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Old May 12, 2007 | 01:31 PM
  #5  
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Figure 1


Previous Design Sensor
Magnet will pick up 1.25 lb pump gears.
New Design Sensor
Magnet struggles with .5 ox nail clippers




Figure 2 Signal pattern at 2000 RPM


Previous Design Sensor New Design Sensor




Figure 3



(Click image for larger view)


There are a few points to consider. If you take a closer look at the wave-forms in figure 2, you’ll see there’s a sharp pulse upward (positive), then a sharp pulse downward (negative), followed by a relatively longer flat line (zero).

Here is an analysis of the wave-form in figure 5 and how the magnetic field contributes to sensor output. This gives you a little insight into what you’re looking at on your oscilloscope or graphing meter. This also applies to many other pulse generator type sensors used in automobiles.

Figure 4



(Click image for larger view)




Figure 5



(Click image for larger view)


Four "tabs" on the CD4E reverse clutch hub, which rotates as an assembly with the input drum, trigger the TSS. The sensor is simply a magnet with a coil wound around it. The positive pulse is when the tab enters the sensor’s magnetic field. The magnetic field "reaches out" and stretches toward the tab, trying to pull it in, like any magnet would do to a piece of iron. Whenever the magnetic field changes shape, it induces voltage into the sensor windings. The voltage is proportional to the rate of change of the magnetic field, which gives you a voltage pulse.

As the tab approaches the center of the sensor, the voltage starts dropping back to zero, which you see after the positive peak in the pattern. This is because the magnetic field is changing less and less as the tab approaches "dead center," or the center of the sensor’s magnetic field.

The negative pulse that follows starts when the tab is moving out of the sensor’s magnetic field. The magnetic field pulls back into the sensor as the tab moves out of its reach, which induces voltage in the opposite direction, creating the negative voltage pulse.

The relatively long flat line between pulses is the distance between the tabs.

The height (amplitude) of the voltage pulses are relative to how quickly the magnetic field changes, which is based on turbine RPM and how quickly the magnetic field responds at high RPM. A weaker, and subsequently smaller, magnetic field reduces the sensor’s ability to induce voltage into the windings.

The weaker magnetic field also means the distance from the tab to the end of the sensor (air gap) is going to have a greater effect on sensor output. For example, while the previous design sensor’s signal voltage output might not be reduced severely by a 0.100" clearance, the effect on the new design sensor’s signal voltage output can be much greater.

The PCM counts the number of pulses (four pulses per revolution). The PCM has a threshold voltage level the pulse has to exceed before it counts the pulse, typically about half a volt. Volt AC, reading on a DMM (Digital Multi Meter), or about a 1.3 volt pulse height on a scope. The minimum signal should be about 1 volt AC on a DMM, or a 2 volt pulse height on a scope, for a safe margin. The reason for the difference in DMM and oscilloscope readings is because a DMM is calibrated to indicate the RMS (Root Mean Square) voltage of a sine wave, which has a constantly changing voltage level. RMS voltage is simply the equivalent DC working voltage, which is less than the actual peak voltage shown on an oscilloscope. RMS is calculated because alternating current cannot perform very much work during the periods it is passing through zero volts. The TSS signal also sits at zero for a considerable length of time between pulses, which can also cause the DMM to indicate a lower voltage. A DMM cannot measure this type of signal accurately, but it will give you a good indication of the signal voltage level as long as you know what to look for. The uneven pulse heights in figure 2 are characteristic of electrical interference. This can become a problem when the signal voltage is weak, as some pulses can fall below the threshold and won’t be counted.

With the new design sensor, air gap and geartrain endplay become critical for sensor output. Keep this in mind if you’re unable to locate the previous design sensor. The maximum air gap shouldn’t exceed .030". Comparing the two sensors in figure 6, notice that the previous design sensor had an exposed pole piece, the new design sensor doesn’t. The exposed pole piece gave the magnetic field more exposure to the tab, which increased signal strength.

Figure 6



(Click image for larger view)


The previous design sensor had a black plastic body with a metal holddown bracket. It measured about 180 ohms at 75º F.
 
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Old May 12, 2007 | 01:33 PM
  #6  
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You can identify the new design sensor (P/N XS7Z-7M101-KA) by its white plastic body and integrated mounting tab (figure 4). It measures about 800 ohms at 75º F. Currently, it is the only replacement sensor offered by Ford. It seems to be a problem mainly in older vehicles where some of the aforementioned factors come into play. One of my test cars was an unmolested 2000 Contour, which had no problem with the new design sensor.

If you’re having persistent TCC or ratio error codes, take a look under the front left fender. If you see the telltale white plastic sensor, see if you can get a hold of one of the following part numbers: F7RZ-7M101-AA or F3RZ-7M101-A. Use caution, as Ford has superceded these part numbers to the new design, so make certain your dealer or parts supplier has the actual part number. You might get lucky and your local dealer or parts supplier could still have the previous design sensor in stock. Otherwise, the best recommendation is to find a good used sensor.
 
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Old May 12, 2007 | 02:30 PM
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The CD4E is a piece of junk. So are all the raggedy *** vehicles they come in.
 
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Old May 12, 2007 | 03:46 PM
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Originally Posted by Quintin
The CD4E is a piece of junk. So are all the raggedy *** vehicles they come in.
I couldn't have stated it better.

That CD4E can't even handle a i4 putting out 120 hp. How the heck will it react with a 200 hp duratec engine... like duh Ford and Mazda.

I betcha my riding lawn mower engine could break that CD4E.
 
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Old May 13, 2007 | 01:09 PM
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I think they have finally made this unit useable. The early ones were completely junk. You'd open them up and find every bushing in them completely fried and a good lb of brass in the bottom. Alot of those issues were caused by faulty grounds. I always add a second ground strap to all of these transmissions. You can never have too good of a ground.
Everyone talls about horsepower as if it is what kills transmissions. Weight is more important. It's just like with towing a load too heavy. I have overloaded my ranger beyond what any small truck should ever handle. It got up to speed. Wasn't very nice to stop. Thank the lord I had a manual or it would still be moving.
Alan
 
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