(Avoid a Square Peg in a Round Hole) - Transmission Digest

(Avoid a Square Peg in a Round Hole)

Who knew back in 1989 when the E4OD was launched what the time-frame footprint would be or how many changes would occur, let alone that it would grow into a five speed automatic? For the repair industry, the big RWD family of transmissions has been pretty profitable due to failures, but at times somewhat troublesome due to rebuilding issues and component upgrades. Some upgrades have been fairly straightforward and inexpensive while others were more complex and costly. The four speeds certainly had modifications and upgrades; however, those models pale in comparison to the five speeds.

(Avoid a Square Peg in a Round Hole)

Technically Speaking

Author: Mike Riley, Technical Editor
Subject Matter: O.D. Sun Gear Design
Unit: E4OD/5R110W

Technically Speaking

  • Author: Mike Riley, Technical Editor
  • Subject Matter: O.D. Sun Gear Design
  • Unit: E4OD/5R110W

Who knew back in 1989 when the E4OD was launched what the time-frame footprint would be or how many changes would occur, let alone that it would grow into a five speed automatic?

For the repair industry, the big RWD family of transmissions has been pretty profitable due to failures, but at times somewhat troublesome due to rebuilding issues and component upgrades. Some upgrades have been fairly straightforward and inexpensive while others were more complex and costly. The four speeds certainly had modifications and upgrades; however, those models pale in comparison to the five speeds.

Although basic architecture is the same between four- and-five speed units, component interchangeability is limited between the models. One small item did migrate over to the five-speed transmission, although with a couple of tweaks beyond the E4OD.

The E4OD, 4R100 and 5R110W OD (overdrive) sun gear has always been attached to the coast clutch drum, either by a spline slip-fit or press-fit design (Figure 1).

The first design OD sun gear that went into the 1989 E4OD had teeth that were the same diameter and style from one end of the gear to the other. The gear included a rounded backup snap ring for positioning in the coast drum as well as a bore bushing for support on the input shaft. The gear was a slip-fit into the drum. The coast drum was cast iron.

By 1998, Ford decided to give the E4OD a facelift by releasing the 4R100. Although some changes did occur to the E4OD, the 4R100 consisted of several upgrades that would not interchange with the earlier models. One change was to the coast clutch drum, which was no longer cast iron, but steel (GROB). In addition to the material change was the OD sun-gear spline design. The bore of the drum was changed as was the sun-gear tooth design. The parts of the teeth that mesh with the drum were more blunt than on the E4OD sun gear, creating a step in the gear. The new design was a press-fit as well.

Ford designed the new sun to work with both cast and steel drums. The E4OD sun gear (part #E9TZ-7D063B) became NLA and was superseded by the 4R100 gear (part #F81Z-7D063AA). When using the new gear in a steel drum, merely press it in. When using the gear in a cast drum however, a square-cut snap ring must also be used for back-up.

Including 5R110W models, there are now four types of OD sun gears (Figure 2). The cast drum sun-gear is on the left with uniform teeth and a rounded snap-ring. Next to that gear is the combo cast/steel drum design with blunt teeth and square-cut snap ring to use with a cast drum type. The two gears on the right are the 03-06 and 07-up 5R110W sun gears.

Due to pump and coast drum design changes, the 03-06 5R110W sun gear is slightly different from the 4R100 gear. The coast drum bushing position is different on 5R110W models than E4OD/4R100 and the sun gear no longer uses a bushing. The bore of the gear was reduced accordingly (Figure 3). The early 5R110W gear (part #3C3Z-7D063AA) is also NLA due to design changes in 2007. An entire update package now is available to retro to 2003. If a gear is needed for 03-06, the 4R100 gear can be used by removing the bushing.

The 2007 upgrade involves the entire overdrive planet set and coast clutch assembly, including the sun-gear tooth count. Previous sun gears had 38 teeth whereas 2007-up gears have 41. In addition, there is a slight diameter difference between the types (approximately .025). Ensure that you choose the correct gear before pressing into the drum or damage will occur. The 41-tooth gear part number is 7C3Z-7D063C.

All coast clutch drums contained the overdrive OWC (One Way Clutch) rather a sprag, roller clutch or diode. The E4OD cast drum had inner race splines for the entire OWC assembly (Figure 4). The sun gear fit cannot be too tight or the cast drum could crack.

In addition to the 4R100 drum being steel, the OWC design was also changed so that the inner race is now part of the drum (Figure 5). The modification also meant that the sun gear can have a higher press fit.

The 5R110W coast clutch drum has undergone several changes and is much different from E4OD/4R100 drums. The OWC is a mechanical diode which has been updated a few times and the drum may have a PTO gear depending on the model (Figure 6).

Due to the 2007 upgrade, the drum spline count became 41 from the previous 38 splines so always count the splines before interchanging. The 2007-up drum may have gas or diesel stamped into the front of the drum. The drums are the same, it’s the diode that’s different.

Remember, don’t put a square peg in a round hole.

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