January 09, 2018

There's a New Hub in Town

After a considerable effort to design and test a replacement impeller hub for the Ford 6R140 torque converter, Sonnax is pleased to announce the release of FD-90-140G — the first for this unit available in the aftermarket. In comparison to some of our other flanged impeller hubs, this is not an inexpensive piece, however this is not an average impeller hub. The Sonnax engineering team went above and beyond to develop a quality hub that can be successfully installed into this cumbersome unit.

If you have ever tried to fit the 6R140 converter onto a transmission, you know that it can be difficult to install the converter into the pump. The unit is quite heavy, and the two sets of splines (O.D. splines drive the pump gear and, if applicable, the I.D. splines drive the PTO) have a very tight tolerance/fit. In addition, the O.D. of this thin-walled impeller hub rides on a drawn cup needle bearing. Converter rebuilders report that many virgin cores show evidence of wear/damage at the location where the needle bearing rides (not a bushing) on the hub, necessitating impeller hub replacement.

It’s strongly recommended that the OE pump bearing be replaced when installing a replacement. Rebuilders know too well that needle bearings may look OK, but 100% replacement is part of a quality build. An OE replacement converter hub support pump bearing is available to transmission rebuilders from Sonnax under part number 126202.

The Sonnax impeller hub maintains very close tolerances on spline fit, I.D./O.D. dimensions and concentricity to precisely match OE function. This posed quite a challenge when designing an aftermarket part, though. The O.D. of the hub rides on a needle bearing, so it was critical that proper hardness of that surface was achieved. On the other hand, because the hub is thin walled and has splines at each end, it was a precise process to get the hardness of the hub within spec without distorting the roundness or fit of the hardened splines.

So, you may be asking: why did the OEM complicate matters by creating such a precision interface between the impeller hub and the transmission pump? Well, they actually have it a little easier, because they were able to select a very high carbon content alloy that helps keep the thin-walled hub’s tolerances and hardness in spec. Unfortunately, using the same material as the OEM is not a good choice for an aftermarket replacement impeller hub. While their alloy lets the OEM maintain its specs, special welding processes and equipment are required for installation. Therefore, not only did Sonnax need to design the FD-90-140G to excel at form, fit and function, we also had to pay considerable attention to the installation — or “weldability” — of the hub. Sonnax experimented with various alloys and hardening processes to provide you with a part that meets the required performance specs AND is easily welded. If Sonnax simply offered a replacement hub made from the same alloy as the OE, it would likely crack if you were to weld it in place using the standard MIG welding equipment and processes common to torque converter remanufacturers.

Tips for Successful 6R140 Impeller Hub Installation

1. Take the Chill Off when Welding Sonnax FD-90-140G

While the alloy used to manufacture the Sonnax hub is easily welded, it’s not quite as forgiving as the material used in the bulk of Sonnax impeller hubs. The hub should be — at minimum — at shop temperature when welding it into the 6R140 impeller. If you are in a cold weather climate and you store cores and/or components in an unheated area, you should let parts warm up to room temperature before welding. After welding the hub into place, let the assembly cool slowly, without quenching the parts. Immediately dousing the welded impeller into your leak test tank (to make it easier to handle, for example) would likely cause the hub to crack.

2. Develop Techniques that Guarantee Minimal Runout

Speaking of welding, it’s worth noting that there are SAE and other papers written about the unique overall design of the 6R140 converter. Some of that information discusses how the OE parts require a very tight pilot-to-impeller hub runout tolerance to help reduce NVH issues and ensure proper operation and component durability. For the aftermarket, that translates into a need for precise fixtures and procedures that will keep runout to an absolute minimum. Because this is such a large and heavy converter, and the impeller hub has an outside diameter more than 2.5", it might be worthwhile to review the equipment and process you use to weld the converter body together. A little analysis and planning up front could eliminate problems later on.

Repairing the 6R140 impeller hub is a more demanding job than replacing the tube-style hubs you see every day, like
some 4L60 applications. Check out the new FD-90-140G. This one-of-a-kind component meets all of the demands of form, fit and function, PLUS is engineered to be weldable and user friendly. It’s a great new product to help prevent comebacks the next time you rebuild a 6R140.

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While Sonnax makes every effort to ensure the accuracy of technical articles at time of publication, we assume no liability for inaccuracies or for information which may become outdated or obsolete over time.