6T45 Sprag Clutch

If your GM crossover or sedan with the 6T45 six-speed sits in Drive and barely creeps, launches in what feels like second, or slips on takeoff yet pulls fine once it upshifts, the low one-way clutch is one of the first parts to suspect. This is a used OEM 6T45 sprag clutch, the mechanical one-way clutch that carries the load in first gear. The 6T45 is the higher-torque version of the 6T40 family and shows up in vehicles such as the 2.4L Equinox and Terrain, plus other front-drive GM models from the 2008-2019 span.

What the sprag clutch does in a 6T45

The 6T45 makes six speeds with five hydraulic clutches (1-2-3-4, 2-6, 3-5-Reverse, 4-5-6 and low/reverse) and one mechanical one-way clutch. In Drive first, the one-way clutch holds the reaction member while the 1-2-3-4 clutch is applied, so first gear needs no low/reverse clutch at all. When the TEHCM commands second by applying the 2-6 clutch, the one-way clutch simply overruns and lets go. That is why the 1-2 upshift on these units is so smooth, and also why a worn sprag shows up almost entirely in first. In manual first and in reverse, the low/reverse clutch is applied hydraulically and takes over the holding job.

Symptoms of a failed 6T45 one-way clutch

• No first gear in Drive: the engine revs and the vehicle barely moves until the transmission upshifts
• Slipping or a neutral feeling on takeoff that clears up in second and above
• Normal reverse and normal manual first, because the low/reverse clutch holds in those ranges
• Clunk or ratcheting noise while coasting down to a stop
• Metal debris on the pan magnet if the rollers or races have broken up

How to confirm it before buying

The quickest road test is to compare Drive with manual first. If the vehicle will not pull from a stop in Drive but drives away normally when you select first manually, the low/reverse clutch is covering for a one-way clutch that is freewheeling in both directions. Scan for codes too. A no-first complaint that comes with P2723 or P0878 points toward the 1-2-3-4 clutch, its bonded piston or a pressure control solenoid, not the sprag; GM bulletin PI1131 documents solenoid faults that drop gears. Our 6T40 and 6T45 common problems guide covers the cracked 1-2-3-4 piston, and the delayed engagement guide helps if the problem is really a slow bump into gear. On the bench, the sprag should lock in one direction and spin freely in the other with no rough spots.

Fitment

This listing is for the 6T45 with no specific year range, and it is a used original-equipment part rather than an aftermarket copy. GM built the 6T40/6T45 in three generations, and Sonnax notes that many parts do not interchange between Gen 1, Gen 2 and Gen 3. Before ordering, compare the outer diameter, spline count and race design against the one-way clutch in your unit, and check the photo. If you are not sure which generation you have, send us your year and VIN and we will check it. For a lower-cost option on 2008-2013 units there is also the 6T45 sprag clutch for 2008-2013, and if your unit is a 2008 build we also stock the remanufactured 2008 6T45 sprag.

Install notes

• Note the freewheel direction of the old sprag before you remove it, and install the replacement the same way; a reversed one-way clutch gives you no first and a lockup in another range.
• Inspect the inner and outer races. Any pitting, brinelling or scoring means the race needs replacement too.
• A sprag that failed usually sent debris through the case. Flush the cooler and replace the filter; if the clutches are burnt, the 6T45 master rebuild kit for 2008-2011 or the bonded piston set is the time to do them while the unit is apart.
• Refill with Dexron VI and set the level hot at the check plug, following our 6T40 fluid change guide.
• Clear the adapts and drive through several light-throttle shift cycles so the TEHCM can relearn clutch fill times.

Will a bad sprag stop a 6T45 from moving in reverse?

Usually not. Reverse uses the low/reverse and 3-5-R clutches, so a freewheeling one-way clutch typically leaves reverse working while Drive first slips or is missing.

Does this fit a 6T40 too?

The 6T40 and 6T45 are closely related, but internal parts differ by model and by generation. Compare the part to your old one-way clutch or send us your year and VIN before ordering.

What should I replace with the one-way clutch?

Replace the filter, flush the cooler and inspect the races. If the clutch packs are glazed or the pan is full of debris, a full rebuild kit with new bonded pistons is the better repair.

What fluid does the 6T45 use?

Dexron VI. The level is set at operating temperature through the check plug, not by a dipstick, so follow the hot level-check procedure after the repair.

Do I need a relearn after installing it?

Clear the transmission adapts with a scan tool and drive through gentle shift cycles. The one-way clutch itself has no adjustment, but the clutches it works with are adaptively controlled.

• 6T40 Common Problems and Fixes
• 6T40 Delayed Engagement: Causes and Fix
• 6T40 Fluid Change Cost
• 6T40 Shift Solenoid Symptoms and Replacement