Shift Pointers
- Subject: Damage caused by blocked lube hole, faulty ground
- Unit: AX4S
- Vehicle Applications: Ford passenger cars
- Essential Reading: Rebuilder, Diagnostician
- Author: Pete Luban, ATSG
Our first tale is one of those situations in which you are in the middle of nowhere and all of a sudden a warning lamp comes on. This person, whom we will call Mr. Public, was driving his Ford Taurus equipped with an AX4S on a lonely stretch of road at night when suddenly the transmission-temperature lamp came on. Fortunately, Mr. Public was able to limp the car into the closest town, where he took the car to the local transmission shop the next morning.
Upon initial inspection the shop’s technician checked the fluid and found that it was severely burnt. The next step was to drop the pan and see what kind of damage might have occurred. Considering the condition of the fluid, there was hardly anything in the pan so the transmission was removed for inspection.
When the oil-pump driveshaft was removed one of the sealing rings was a mess and there was some pitting on the shaft where the bearing rides (Figure 1). A number of the plastic washers were also melted, but not much else was found in the way of real damage except when the technician examined the channel plate.
What you see in Figure 2 is the result of that examination as well as the cause of all the problems that occurred.
The delivery sleeve in the center of the channel plate had turned, completely blocking the lube hole in the channel-plate casting (Figure 3). Fortunately for Mr. Public he got the car in for repairs before severe damage to the gear train took place.
Our next situation concerns a different Ford vehicle with an AX4S that came into the shop because it was slipping. Inspection of this transmission revealed damage to the driven sprocket and the driven-sprocket support (figures 4 and 5). The plastic thrust washer between the driven sprocket and the support is impregnated with metal, which you also can see in Figure 5. At this time the technician looked for worn bushings or bearings but found none other than the oil-pump driveshaft bearing.
Further inspection found no reason for the existing hard-part damage, and this made the technician suspicious of a possible underlying problem that may have been pre-existing.
When the transmission was reinstalled the technician checked the battery ground cable and found nothing wrong with it. His next step was to place his multimeter between the transmission case and the negative battery connection to do a voltage-drop test, and he found quite a bit of voltage present.
That’s right, the damage to the driven sprocket and support were the result of a bad ground. In this instance a ground strap installed from a bellhousing bolt to the negative-battery-cable accessory lead removed the voltage from the transmission case.
Just a couple of things to be aware of in your day-to-day experiences.
Special thanks to Bob from Paradise Transmissions in Key West, Fla., for sharing his experiences and photos with us.
