6F50 Sprag Clutch

Rebuilders and DIY owners tracking down a slip in first gear on a V6 Ford Edge, Flex, Taurus, Explorer, Lincoln MKX, MKS or MKT usually end up looking at the low one-way clutch in the 6F50 transaxle. This listing is a used original 6F50 one-way clutch element, the caged ring of locking elements pictured, pulled from a running unit and offered as an economical way to replace one that has worn, broken or lost its springs.

How the one-way clutch works in the 6F50

The 6F50 shares its basic gear train with the GM 6T70: five clutches and a single diode-style low one-way clutch. In first gear in Drive the 1-2-3-4 clutch is applied and the one-way clutch holds the reaction member; it is the only thing keeping the gearset from spinning backward under load. When engine braking is wanted in first, the low/reverse clutch is applied as well. As the transaxle shifts to second, the element simply overruns, which is how Ford gets a clean 1-2 shift without timing one clutch off against another. Because it carries full first-gear reaction torque every time the vehicle pulls away, worn elements show up first on heavy launches and when towing.

Signs your 6F50 one-way clutch is failing

• Engine revs but the vehicle barely moves in Drive from a stop
• Delayed engagement into first that improves once the transaxle upshifts
• First holds with engine braking (low/reverse clutch on) but slips in normal Drive
• A thump or ratcheting noise when coasting down or on light throttle
• Broken element pieces or bright steel particles on the pan magnet

Diagnosing it before you replace it

Many 6F50 slip complaints are hydraulic, not mechanical, so start with codes, fluid level and a line pressure check. Then compare how first behaves in Drive with how it behaves when the low/reverse clutch is applied. A one-way clutch fault slips only in Drive; a forward clutch or pressure problem slips in both. Our 6F35 and 6F50 problems guide explains the regulator valve wear common to this Ford family, which can mimic a mechanical slip. With the unit apart, roll each element by hand and look for flat spots, cracked cage segments and wear marks on both races.

Fitment

This part is listed for the Ford 6F50, and the same family includes the heavier-duty 6F55. No year range is given for this listing, so measure before you buy: compare the element count, cage diameter and width with the one you removed, or send us your year and VIN to check. Sonnax lists the diode one-way clutch among the primary differences between the Ford 6F50 and the GM 6T70, so do not assume a GM part will swap in, and do not use a 6F35 one-way clutch, which is a smaller unit. Browse every part we carry for this Ford family on the 6F35 and 6F50 collection.

Install notes

• This is a used part: clean it, inspect every element and spring, and confirm it locks and overruns smoothly between the races before assembly.
• Check direction of rotation before closing the case; a reversed element binds the gearset.
• Replace the races if they show pitting, scoring or heat color, since the element rides directly on them.
• If the valve body was part of the original complaint, consider the 6F50 valve body for 2006-2015, and on a full overhaul a 6F50 shift kit for 2007-2018 helps with the regulator issues.
• Refill with Mercon LV, set the level hot, clear the TCM adaptives and road test several launches before returning the vehicle.

What exactly is included?

The one-way clutch element pictured, the caged ring of locking elements. It is a used original part and does not include the inner or outer race.

Does it fit the 6F55?

The 6F55 is the heavier-duty version of the 6F50. Compare the element count, diameter and width to your old part, or send your year and VIN and we will confirm.

Can I use a GM 6T70 one-way clutch instead?

Do not assume so. Sonnax lists the diode one-way clutch as one of the primary differences between the Ford 6F50 and GM 6T70.

Why does my 6F50 slip only in first?

First gear in Drive relies on the one-way clutch to hold the reaction member. If first is fine with the low/reverse clutch applied but slips in Drive, the one-way clutch is the usual cause.

What fluid and relearn do I need afterward?

Use Mercon LV, check the level hot, then clear the adaptive values with a scan tool and make several gentle launches so the TCM relearns.

• Ford 6F35 Transmission Problems: Real Causes and the Fixes That Last