Fun With Transmissions - March - 2019

Ford’s Latest Torque Converter Has Things a Bit Backward

Over the years, torque converters have come in many shapes and sizes. From the huge, bolt-together cast iron powerglide converters (anyone beside me remember those?) to the small Dodge 845RE multidisc converter found behind the 3.7L Pentastar motor.

The new Ford 10-speed that comes in the 2017-up F-150s and Mustangs has a converter that falls just above small and well below large. This style of converter is also used with the GM version of this 10-speed design, called the 10L90.

In this edition of Fun with Transmissions, we’re going to check out the guts of the new design torque converter and discover what makes it different from those we’re used to seeing in other lockup torque converters.

Usually in our workaday world, we don’t pay much attention to the converter. We rebuild the transmission; put it on the jack; pull the converter out of the box, all shiny and freshly painted; prefill it with the proper fluid; lube the hub; install it into the trans; and off we go. Keep in mind, there’s a ton of play in this converter when moving the internal parts around on the bench. No worries; this is totally normal (figure 1).

Wait a second! How about we get this round thing cut open and have a look at what’s inside? We’ve done it before and have gotten used to seeing the basic parts of the converter. They all have similar components: the impeller, turbine, stator, and lockup clutch.

These items may be designed differently but they all perform the same basic functions: to allow the driver to sit at idle, in gear, at a stop, and to multiply torque when taking off again. Okay, and to lock up and conserve fuel economy.

In an effort to increase fuel economy, more and more manufacturers have gotten pretty creative. We have the start-stop systems built into today’s automatics, where the engine shuts off at a stop and starts back up when we apply the gas.

We also have lockup clutches coming on at ridiculously low speeds to eliminate the built-in inefficiency of the torque converter. In some cases, the lockup clutch is applied in all forward ranges except low gear (figure 2).

This unit, being a 10-speed, isn’t going to be spending a whole lot of time in first gear, so we know the converter clutch is going to be coming on way sooner. Quite a difference from an old-style 4-speed that would lock up around 45 MPH or so, and only in 4th gear.

CONVERTER DESIGN

There are a couple things that set this converter apart from the rest. The first, and most notable, is the way the friction plate is built into the turbine housing and the apply surface is milled into the housing on the transmission side of the converter (figure 3). Reconditioning this apply surface will present quite a challenge to converter rebuilders. The angle and surface preparations will be key factors here.

Previous designs had the friction plate bonded to a separate plate on the engine side of the converter. This means, when the converter clutch was applied, the friction material would get pushed away from the engine and toward the transmission. Completely backward from everything else out there!

Second, the friction material is bonded to a cone-shaped, slanted surface (figure 4). This is going to be another challenge for the converter rebuilding industry. Bonding machines have been built to service flat surfaces, so there will definitely be a retooling period before they’re ready to handle this type of friction bonding procedure.

The good news here is that the friction material has a flat surface where it applies to the cover (figure 5).

LARGE DAMPER ASSEMBLY

Because the converter clutch is being applied at low vehicle speeds, it brings a lot of low-level noises into play, such as droning and engine vibrations that the torque converter would normally dissipate.

To take up those engine pulses, there’s a substantial damper assembly built into this converter (figure 6). The first thing you’ll notice about this robust damper assembly is its size: The assembly is just as thick as the turbine that it’s assembled to! Remember, this unit spends more time in lockup mode than it does in torque converter mode.

Second, you’ll notice the drive hub part of the damper — the part that splines to the input shaft — is very loose. We’ve seen a couple of these units apart and this is totally normal (figure 7).

Finally, there are no seals or sealing rings involved with lockup operation. There’s one sealing ring on the stator support, and it really just controls drainback (figure 8).

This torque converter has all the basic parts and a converter clutch that works backward from what we’ve seen in years past.

There are going to be a lot of this type of converters to service in the coming years. The correct tooling for the bonding process will show up eventually. The procedure for resurfacing the apply area on pump side of the converter will also be worked out in time.

Once these two processes get worked out, rebuilding these backward converters will be commonplace. And, as always, when things work out, it’s easy to have fun with transmissions!