Shift complaints on a Traverse come in a few flavors: a bang into Drive or Reverse, a hard or late 2-3 or 3-4, a flare on the 3-4, a shudder around the 2-3/3-2, or a shift indicator that shows the wrong gear or nothing at all. The 2009-2017 Traverse carries the 6T75, the heavy-duty member of GM's 6T70/6T75 six-speed family, behind the 3.6L V6 [6]. GM's service information breaks shift complaints out by symptom and by clutch, and that is the way to attack them: pin down which shift is wrong, then go after the one clutch, valve or switch that controls it. Numbers in brackets point to the Sources list at the bottom.
First, rule out shifts that are supposed to happen
Some "shift problems" are the calibration doing its job. The 2012 Traverse owner manual describes Automatic Engine Grade Braking, which commands downshifts on its own on a downhill grade to hold speed, in Drive and in Tow/Haul [6]. A customer who feels the transmission drop a gear coasting down a hill with a light brake application is feeling that feature, not a fault. Tow/Haul (where equipped, button under the climate controls) also holds gears longer for heavy loads [6].
The manual also covers Electronic Range Select. With the lever in L and a number shown next to it, that number is the highest gear the transmission is allowed to use. With 4 displayed, it shifts 1 through 4 by itself and will not go to 5th until the plus button is pressed or the lever goes back to D. It will also refuse a minus-button downshift if engine speed is too high [6]. A Traverse "stuck in 4th" with an L4 on the cluster is a driver setting. Look at the cluster before you look at the transmission.
What the cluster says counts in the other direction too. SERVICE TRANSMISSION means the TCM has found a problem, and TRANSMISSION HOT IDLE ENGINE means the fluid is overheating; the manual warns that driving on it can damage the transmission [6]. Either message plus a shift complaint is a real fault.
Get the basics clean before you diagnose a shift
Three things come first on every 6T75 shift complaint: codes, fluid and adapts.
- Engine codes. GM's harsh-shift checklist starts at the engine. If the engine controller tells the TCM that its torque signal is inaccurate, the transmission commands high line pressure, and every shift gets firm [3]. A misfire or MAF code is a transmission complaint waiting to happen.
- Fluid level and type. GM lists correct fluid level as a harsh-engagement check [3]. The Traverse takes DEXRON-VI, about 5.0 L (5.3 qt) on a drain-and-refill, and the fluid will not reach the end of the dipstick unless the unit is at operating temperature [6]. ATRA's level check calls for a level surface, the engine idling, and fluid at 180 to 200 degrees F [4]. A cold check reads low, gets topped off, and the unit foams once it warms up.
- Adapts. GM says Transmission Adaptive Values Learn must be run after an overhaul, a valve body repair or replacement, a control solenoid valve assembly replacement, a TCM software update, or "any service in response to a shift quality concern" [3]. Skipping it can leave poor shift quality and set DTCs on its own.
Running Transmission Adaptive Values Learn correctly
The procedure is in the scan tool under Module Diagnosis, Transmission Control Module, Configurations/Reset Functions. GM's preconditions: drive wheels blocked, parking and service brakes applied, zero throttle with no external RPM control, TFT between 70 and 100 C (158-212 F), and the selector cycled Park to Reverse three times to purge air from the reverse clutches. When it finishes, shut the engine off and let the TCM power down; the unit stays in a neutral state until you restart [3].
If it will not run, GM's troubleshooting list is worth reading closely: no active DTCs, brakes and brake switch working, engine RPM able to rise above 1,500 at the test entrance, Park/Neutral switch adjusted and working, the vehicle not moving or vibrating, clutches properly assembled, and line pressure control able to reach 1,000 kPa [3]. A learn that aborts every time on a known-good vehicle is itself a clue that line pressure is not making spec.
Harsh engagement into Drive or Reverse
GM's Harsh Garage Shift chart lists these checks [3]:
- Idle line pressure. GM's check is whether line pressure at idle is below 800 kPa (about 116 psi). Above that, the engagement will be hard.
- Stuck valves in the lower valve body, particularly the boost valves.
- A damaged or fatigued 1-2-3-4 clutch wave plate or low and reverse clutch wave plate, and stripped or worn 1-2-3-4 clutch plate splines.
- An improperly positioned or plugged low/reverse piston air bleed.
- Stripped or sheared splines on the low and reverse clutch (one-way clutch) assembly, and worn or stripped ring gear splines on the input carrier.
The spline items matter. A clunk into gear with lash you can feel in the axle is often mechanical, not hydraulic, and no valve body will fix it.
Harsh or late 3rd, 5th and Reverse
Third, fifth and reverse share the 3-5-R clutch, so when all three are harsh or late, GM points at that clutch: improper plate surface finish, a fatigued 3-5-R waved plate, leaking 3-5-R piston seals, a warped 3-5-R/4-5-6 housing, and plugged oil passages or air bleed in that housing [3]. ATRA notes the 3-5-R wave plate is the one most likely to break in this family, and that a broken plate is the usual find behind a no 3rd, 5th or reverse with P0776 [4]. A late or flared 3rd and 5th on an early Traverse is often the warning before the plate lets go. Sonnax's guidance on wave plates: on a 2011 or earlier unit, update all of them; on 2012 and later, replace the 3-5-R plate [5].
The 3-4 shift: flare, harsh or bind
The 3-4 is where Traverse complaints pile up, and there are three distinct causes.
Harsh 4th, 5th and 6th: the 4-5-6 clutch
The 4-5-6 clutch comes on for the 3-4 and stays on through 6th. GM's checklist for harsh 4th, 5th and 6th shifts: leaking 4-5-6 piston or piston seals, a plugged or restricted piston dam air bleed, a fatigued piston spring, leaking dam seals or a damaged dam, improper plate surface finish, and porosity, seal groove damage or plugged passages in the 3-5-R/4-5-6 housing [3].
3-4 flare or harsh: the 4-5-6 accumulator
Sonnax ties a worn 4-5-6 accumulator piston bore in the valve body to a 3-4 flare, a harsh 3-4, a burned 4-5-6 clutch, ratio codes and slipping [5]. That is the valve body side of the same complaint. If the 4-5-6 clutch pack measures fine and the seals hold air, look here.
3-4 or 4-3 bind, possible P0797
ATRA documents a tie-up on the 3-4 or 4-3 shift on 6T70 and 6T75 units, sometimes with P0797. The cause is a worn ring groove on the case cover hub sleeve, which leaks between the 3-5-R and 4-5-6 clutch circuits, so both clutches are partly applied at once [4]. Pull the hub from the rear case cover and check the rings with a feeler gauge. ATRA's maximum clearance between the ring and the edge of the groove is 0.007 in.; past that, replace the case cover [4]. New rings in a worn groove will bind again.
Harsh or late 2nd and 6th
Second and sixth share the 2-6 clutch, which lives in the case cover. GM's checks: worn or improperly finished 2-6 clutch plates and backing plate, a fatigued 2-6 piston cushion spring, a damaged or broken 2-6 piston with damaged, worn or delaminating seals, and a fatigued 2-6 piston return spring [3]. When only 1-2 and 5-6 feel wrong, the rest of the unit is usually fine.
2017 Traverse: shudder on the 2-3 or 3-2
GM bulletin 18-NA-358 lists the 2017 Traverse (RPO M7V, M7X) for a severe launch shudder in 1st, a shudder in 4th, or a shudder on the 2-3 upshift or 3-2 downshift, with some owners also reporting flare, slide/bump, slip or harsh shifts. GM traces it to debris in the upper and/or lower valve bodies, or scratched and scored valves that do not move properly [2].
Follow the bulletin's order. Rule out a misfire or driveability problem, and confirm it is not TCC shudder by watching TCC slip during the event. GM allows reproducing a launch shudder by power-braking in 1st for 5 seconds or less, to avoid distressing the 1-2-3-4 clutch [2]. The repair is both valve bodies together, and GM states TEHCM replacement has not been an effective fix for this concern [2]. Before the new valve bodies go in, check the ISS and OSS for collected debris: debris means an internal failure, and if the sensors are clean but the valves are scored, check for a failed final drive bearing [2].
Wrong gear on the display, no PRNDL, or P182E
GM product information PI0269B covers 2009-2011 Traverse (and Enclave, Acadia, Outlook and others) with the 6T70/6T75, built February 2009 through July 2010: check engine light with P182E in the TCM, and in rare cases no PRNDL display [1]. GM's steps: verify shift cable adjustment, verify the ECM Park/Neutral switch status in all ranges, and verify the internal mode switch (IMS) A/B/C/P parameters in all ranges. If P182E does not reset after driving within the DTC's run conditions, replace the IMS (the manual shift detent lever with shaft position switch). If U0101 is set in the brake module, GM says to ignore it; it sets falsely [1].
When the indicator shows the wrong gear, GM's checklist is mechanical first: cable damage, the cable attached and locked at the shifter and at the transmission bracket, the shift lever properly attached to the manual shaft, and a manual shaft that is not twisted, then IMS logic [3]. A mis-read range can give odd engagement and wrong-gear starts that look like a hydraulic problem.
Worn valve body bores and the pressure regulator
Sonnax explains that valve bores in this family wear from the scrubbing action of solenoid frequency and duty cycle, the valve body material, and valve designs that allow side-loading [5]. Two wear points cause shift complaints. A worn pressure regulator bore gives erratic line pressure, burned clutches, TCC apply and release concerns, overheating and poor shift quality. A worn actuator feed limit (AFL) valve, which feeds the solenoids, causes clutch failure, solenoid codes and wrong gear starts [5]. Vacuum-test the valve body before it goes back in, or replace it with one matched to your generation.
Gen 1 vs Gen 2: do not mix parts
For 2013 the 6T75 (RPO M7V, M7X) received a major controls update, so 2013-14 units exist as Gen 1 and Gen 2 [4]. Sonnax lists the Gen 2 changes: a TEHCM with no pressure switches and variable flow solenoids, a new valve body and spacer plate with updated pressure regulator, clutch regulator, boost and actuator feed limit valves, a new 1-2-3-4 piston with notched legs and a nine-plate pack, and a redesigned 3-5-R/4-5-6 housing [5]. Most of those do not back-service Gen 1. A Gen 1 valve body on a Gen 2 case, or the reverse, is a built-in shift complaint. Check the RPO on the glovebox label and confirm it against the unit on the bench.
After the repair: let it learn
Run Transmission Adaptive Values Learn with the preconditions above [3]. Then drive it. ATRA explains the TCM also learns clutch fill volume (CP Learn) during steady driving: the 4-5-6 clutch in 3rd, the 1-2-3-4 and 2-6 clutches in 5th, and the 3-5-R clutch in 6th, and it aborts the learn on rough roads [4]. Give the vehicle steady highway time in 5th and 6th before judging the shift, and tell the customer the first few days of shifts may still be settling in.
Shop the part for this fix: 6T75 bonded piston set
Most of GM's harsh and late shift checks come down to leaking piston seals. This 6T75 bonded piston set (2007-up) from CoreTransmissionParts replaces the pistons with seals molded on, so you are not fighting rolled lip seals on reassembly.
View the 6T75 bonded piston set at CoreTransmissionPartsDoing the whole unit? See the 6T75 rebuild kit with pistons or all 6T75 parts at CoreTransmissionParts.
Need parts for this job?
Our 6T75 parts page has valve bodies by year, shift kits, solenoid kits, pumps, clutch drums and rebuild kits for the Traverse, all on our own checkout. For fluid specs across every unit, see the transmission fluid spec chart.
FAQ
Why does my Chevy Traverse shift hard?
Start with engine codes and fluid. GM says an inaccurate engine torque signal makes the transmission command high line pressure, and idle line pressure should be checked against 800 kPa. After that, which shifts are harsh points at a clutch: 3rd, 5th and reverse is the 3-5-R clutch, 4th through 6th is the 4-5-6 clutch, and 2nd and 6th is the 2-6 clutch.
What causes a 3-4 shift problem on a Traverse?
Three things: leaking 4-5-6 clutch seals or piston, a worn 4-5-6 accumulator bore in the valve body, or a worn ring groove on the case cover hub sleeve that leaks between the 3-5-R and 4-5-6 circuits. ATRA says that last one causes a 3-4 or 4-3 bind, sometimes with P0797, and the maximum ring clearance is 0.007 in.
Do I need to relearn the transmission after a repair?
Yes. GM requires Transmission Adaptive Values Learn after an overhaul, valve body or solenoid body replacement, a TCM update, or any service for a shift quality concern. It needs fluid at 158 to 212 F, brakes applied, and the selector cycled Park to Reverse three times first.
Why does my Traverse downshift by itself going downhill?
That is usually Automatic Engine Grade Braking, which GM describes in the owner manual. It commands downshifts on a downhill grade to hold speed in Drive and Tow/Haul. It is normal behavior, not a transmission fault.
Related guides
Sources
- General Motors, Product Information PI0269B, "Malfunction Indicator Lamp (MIL) - Check Engine Light On, DTC P182E," October 2016 (2009-2011 Traverse and other 6T70/6T75 models built 2/2009-7/2010). Backs the P182E and no-PRNDL symptoms, the cable, Park/Neutral and IMS A/B/C/P checks, IMS replacement, and the false U0101 note. static.nhtsa.gov (PDF)
- General Motors, Service Bulletin 18-NA-358, "Shudder, 2-3 Upshift or 3-2 Downshift Concern," October 2020. Backs the 2017 Traverse RPO M7V/M7X listing, the shudder, flare, slide/bump and harsh symptoms, the valve body debris cause, the 5-second power brake limit, the TEHCM caution, and the ISS/OSS debris and final drive bearing checks. static.nhtsa.gov (PDF)
- General Motors 6T70/6T75 service information (fault diagnosis section, as mirrored on SAAB WIS Online): Harsh Garage Shift (engine torque signal, idle line pressure below 800 kPa, boost valves, wave plates, splines); Harsh or Late Third, Fifth and Reverse; Harsh Fourth, Fifth and Sixth; Harsh or Late Second and Sixth; Shift Indicator Indicates Wrong Gear Selection; Transmission Adaptive Values Learn (when required, TFT 70-100 C, P-R three times, 1,000 kPa line pressure, troubleshooting). Harsh Garage Shift · 3rd/5th/Reverse · 4th/5th/6th · 2nd/6th · Wrong Gear Indicated · Adaptive Values Learn
- ATRA, "6T70 Product Issues and Updates" seminar. Backs the 3-4/4-3 bind with possible P0797, the case cover hub sleeve ring groove leak and 0.007 in. maximum clearance, the 3-5-R wave plate as the most common to break, the 2013 Gen 1 / Gen 2 controls update by RPO, the 180-200 F level check, and the CP Learn gears. atracom (PDF)
- Sonnax, "6T70/6F50 Transaxle" technical webinar. Backs the 4-5-6 accumulator piston symptoms (3-4 flare, 3-4 harsh, burned 4-5-6 clutch), the pressure regulator and AFL valve symptom lists, the causes of valve bore wear, the wave plate guidance by model year, and the Gen 2 change list. sonnax (PDF)
- Chevrolet, 2012 Traverse Owner Manual. Backs Automatic Engine Grade Braking, Tow/Haul, Electronic Range Select behavior, the SERVICE TRANSMISSION and TRANSMISSION HOT IDLE ENGINE messages, DEXRON-VI, the 5.0 L (5.3 qt) drain-and-refill and the dipstick-at-operating-temperature note. assets.gm.com (PDF)