6T70 Acadia Common Problems and Fixes

The GMC Acadia was the first of GM's big three-row crossovers, on sale for the 2007 model year, a year ahead of the Enclave and two years ahead of the Traverse. That head start matters on the bench. The earliest 6T70/6T75 units went into Acadias, and the earliest units are the ones that broke the 3-5-Reverse wave plate. A 2007 or 2008 Acadia that comes in with no reverse is the textbook case. This guide walks the Acadia problems in the order they show up by model year, with the GM bulletin numbers, codes, specs and part numbers behind each one. Numbers in brackets point to the Sources list at the bottom.

What is in an Acadia, and why the RPO label matters

The first-generation Acadia is a 3.6L V6 with a six-speed front-drive automatic. GM's 2012 Acadia owner manual lists one engine, the 3.6L V6 with VIN code D, backed by an automatic [6]. GM's wave plate bulletin and the special coverage that followed it list the 2007-2009 Acadia as a 6T70/6T75 vehicle under RPO MH2, MH4, MH6 or MY9, alongside the Saturn Outlook and Buick Enclave [1][2].

The later trucks are where people order the wrong parts. Shudder bulletin 18-NA-358 lists the 2014-2019 Acadia under four transmission RPOs: M7V and M7X, plus M7U and M7W, which GM added to the Acadia listing in March 2021 [4]. ATRA identifies M7V and M7X as 6T75 codes and M7U and M7W as 6T70 codes [5]. So a late Acadia can carry either the heavy-duty 6T75 or the 6T70, and you cannot tell which from the model name. Read the RPO label in the glovebox before you buy a kit or a valve body.

Generation is the other trap. ATRA explains that the M7W, M7U, M7V and M7X units got a major control system update for the 2013 model year, while units under other RPO codes did not get it until 2014 production. That leaves two versions in 2013, Generation I and Generation II [5]. Pistons, frictions and valve bodies differ between them. Buy for the unit on the bench, not the calendar.

Recommended 6T75 parts

What fixes the Acadia patterns below: a 2007-2012 6T75 overhaul kit for an early unit that broke its 3-5-R wave plate, a 2014-2016 6T75 valve body for the shudder and flare GM traces to valve body debris, and the filter and pan gasket kit for a correct DEXRON-VI service.

6T75 Overhaul Kit 2007-2012

$349.86

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6T75 Valve Body 2014-2016

$211.81

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6T70/6T75 Transmission Filter and Pan Gasket Kit 24223670

$39.99

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1. 2007-2009: no reverse, 3rd or 5th from a broken 3-5-R wave plate

This is the Acadia failure. GM bulletin 09-07-30-012F lists the 2007-2009 Acadia and describes a check engine light, no reverse, and a slip, flare or harsh shift in 3rd and/or 5th. The usual code is P0776, Clutch Pressure Control Solenoid 2 Stuck Off. Any of P0777, P2723, P0717, P0716, P2715 or P2714 can set on its own from the same failure [1].

Here is the mechanism. The 3-5-Reverse clutch has a waved cushion plate. When it cracks, the apply piston over-strokes, the piston seal leaks, and the clutch loses apply [1]. Reverse, 3rd and 5th all need that clutch, so they drop out together. GM says it normally will not happen before about 20,000 miles (32,000 km), and that the debris it throws can upset the speed sensors and the other clutches [1]. That debris is why a code list on one of these can look like three separate problems when it is really one.

ATRA notes the condition primarily affects transmissions built before the 2010 model year [5]. On the Acadia that is the 2007-2009 run, which is three model years of exposure, more than any of the Chevrolet models got.

Coverage: gone, but the parts list is still useful

GM special coverage 14404B covered the 2007-2009 Acadia for 10 years or 120,000 miles from the original in-service date, regardless of ownership, with dealers replacing the 3rd/5th/reverse clutch plate at no charge [2]. Every one of those trucks is now past ten years, so this job comes to the independent shop at full price.

The coverage parts list still makes a good quote sheet. It splits the service seal kit by year: 24269587 for 2007-2008 models and 24269586 for 2009 [2]. Add four reverse clutch fibers 24238954, four flat steels 24258074, the 3-5-R backing plate 24236516, the reverse clutch housing 24223798 and piston 24223803 if required, and nine quarts of DEXRON VI (88861037) [2]. On a heavy three-row truck, plan on the housing and piston being needed rather than hoping they are not.

Confirming it before the unit comes out

ATRA keeps it simple: unplug the transmission and see whether reverse is being prevented electrically. If reverse engages unplugged, the input sun shell, a separate early failure where the welds break, is not the problem [5]. Steel flakes on the pan magnet finish the call.

Do not sell a control solenoid body on P0776 alone. GM states that the control solenoid valve and TCM assembly should not be replaced for any DTC unless the SI diagnostics call for it, and that it should never be washed in a parts cleaner [1]. On these trucks the TCM lives inside that assembly, so condemning it wrongly is an expensive mistake.

The repair that does not come back

GM recommends a new waved plate any time the transmission is apart for any reason. Then the clean-out: separate the case halves, clean the debris from the entire transmission, and replace both the pump fluid filter and the control solenoid filter plate. GM warns that skipping those steps can lead to repeat damage [1]. The updated 3-5-R plate is P/N 24254103 [1].

ATRA goes one step further and recommends the new-design wave plates in every clutch, so the planetary does not get chewed up later: 1-2-3-4 (24259063), 2-6 (24259816), 3-5-R (24254103) and low-reverse (24259817). The 3-5-R is the one most likely to break [5]. On an Acadia that has already broken one plate, I put all four in. The labor is already spent.

2. No movement after the wave plate job (P2723)

ATRA names the Traverse, Acadia, Outlook and Enclave for this one. After a repair that included a new reaction planetary carrier, the truck comes back with no drive and P2723 [5]. Many publications show the reaction carrier and input ring gear as one assembly. In reality the reaction carrier, the input ring gear and its snap ring are serviced as separate pieces, and if the ring gear does not go back onto the new carrier, the vehicle will not move. The fix is to install the ring gear [5]. Lay the old and new assemblies side by side before anything goes into the case.

3. 2009-2011: check engine light with P182E or a blank PRNDL

GM Preliminary Information PI0269B covers the 2009-2011 Acadia, built February 2009 through July 2010, with a check engine light and P182E set in the TCM. In rare cases there is also no PRNDL display [3]. P182E is an internal mode switch (IMS) code, the range sensor on the manual shaft. GM's verification steps, in order [3]:

• Verify the shift cable adjustment.
• Verify the ECM Park/Neutral switch status in every range.
• Verify the IMS A, B, C and P parameters in every range on the scan tool.
• Drive it within the Conditions for Running the DTC and the freeze frame data to try to reset it.

If the code does not come back, GM replaces the IMS, which is the lever, manual shift detent and shaft position switch assembly. If it does come back, continue into circuit and system testing. A U0101 stored in the electronic brake control module is a false set and should be ignored [3]. This is a cable and sensor job. Do not let anyone quote it as a transmission.

4. Bind on the 3-4 or 4-3 shift (P0797)

ATRA lists a 6T70/6T75 complaint of a bind on the 3-4 or 4-3 shift, sometimes with P0797. A worn ring groove on the case cover hub sleeve lets the 3-5-Reverse and 4-5-6 clutch circuits leak into each other, and the unit ties up [5]. Pull the hub from the rear case cover and measure between the edge of the groove and the ring with a feeler gauge. Maximum clearance is 0.007 in. Past that, replace the case cover [5]. A high-mileage Acadia that has towed is a prime candidate.

5. Pressure switch codes: P0752, P0872, P0877, P0989

Before you chase switches or the solenoid body on these, ATRA says to check line pressure at idle, and if it is low, inspect the pump outlet seal for damage [5]. A cut outlet seal starves every circuit, and the pressure switches are just the first thing to report it.

6. 2014-2019: launch shudder, flare and the 2-3 shift

GM bulletin 18-NA-358 covers the 2014-2019 Acadia, first generation and the redesigned second generation alike. The complaint is a severe launch shudder in 1st from a stop, a shudder in 4th while cruising, or a shudder on the 2-3 upshift or 3-2 downshift. It can come with flare, slide/bump, slip or harsh shifts [4]. GM traces it to debris in the upper and/or lower valve bodies, or to valves that are scratched or scored and do not move properly [4]. Work it in the bulletin's order:

• Rule out an engine misfire or driveability problem first.
• Rule out converter clutch shudder by watching TCC slip on the scan tool while the TCC is applied during the event.
• Try to reproduce the launch shudder with a power brake in first, for 5 seconds or less, so you do not distress the 1-2-3-4 clutch [4].

If it reproduces, GM replaces the upper and lower valve bodies at the same time: upper 24281084, lower 24257450, plus kit 24264343 [4]. Two warnings in that bulletin save real money. TEHCM replacement has not been an effective repair, so do not replace it for this concern. And check the input and output speed sensors for collected debris. Debris on the sensors means an internal component is failing. Clean sensors with scratched valves or bores means you check the final drive bearing [4]. A new valve body on top of a failing final drive bearing just gets scratched again.

7. Heat, towing and the TRANSMISSION HOT message

The Acadia cluster can show TRANSMISSION HOT IDLE ENGINE. GM's 2012 manual warns that driving while the fluid is overheating can damage the transmission, and that the repair may not be covered by warranty [6]. The same manual rates the V92 trailer package at 5,200 lb on front and all-wheel drive [6]. A loaded Acadia pulling a camper up a grade in July is exactly the duty cycle that cooks 3-5-R and 1-2-3-4 frictions. When a customer reports that message, ask about towing before you quote.

One thing that looks like heat damage and often is not: ATRA notes some MH2, MH4, MH6 and MY9 converters show dark or blue discoloration, often as circles on the hub side. If the whole converter is not discolored and there is no other sign of overheating, do not replace it [5].

Service specs that keep an Acadia 6T75 alive

Fluid: DEXRON-VI only. The 2012 Acadia manual lists the transmission drain-and-refill at 5.0 L (5.3 qt) and warns that the wrong ATF can cause damage the warranty may not cover [6]. A full overhaul takes far more; the wave plate coverage repair calls for nine quarts [2]. The same manual lists GM power steering fluid (89021184) for the hydraulic power steering, not ATF [6]. Do not top off both from one jug.

Level check: GM says the fluid will not reach the end of the dipstick unless the transmission is at operating temperature [6]. ATRA's procedure is level ground, parking brake on, engine idling one minute, fluid temperature between 180 and 200 degrees F, then read the stick. After a fluid change, reset the transmission oil life monitor [5]. A cold "low" reading is normal, and a cold top-off is how these get overfilled.

Interval: ATRA lists 50,000 miles for severe service and 100,000 miles for regular service, and notes the internal filter is not a service item, replaced only after an internal repair [5]. Most Acadias that tow, idle in school lines or live in hot climates belong on the severe schedule.

After the repair: run Service Fast Learn Adapts with the scan tool, then shut the engine off and let the TCM power down before restarting. A replacement transaxle needs its internal TCM programmed. Lift the converter in and out vertically: the lip seal is inside the converter and gets damaged if the converter goes in at an angle [5].

Quick reference

Need parts for this job?

Our 6T75 parts page has overhaul and rebuild kits, valve bodies, pumps, clutch drums and solenoid kits for the Acadia, all on our own checkout. If your late Acadia's RPO label shows M7U or M7W, use the 6T70 parts page instead. For fluid specs across every unit, see the transmission fluid spec chart.

FAQ

What transmission is in a GMC Acadia?

The first-generation Acadia uses a six-speed front-drive automatic from GM's 6T70/6T75 family behind the 3.6L V6, listed under RPO MH2, MH4, MH6 or MY9 for 2007-2009. GM bulletin 18-NA-358 lists 2014-2019 Acadias under M7V and M7X (6T75) and M7U and M7W (6T70). Check the RPO label in the glovebox before ordering parts.

Why does my Acadia have no reverse?

On a 2007-2009 Acadia the usual cause is a broken 3-5-Reverse clutch wave plate, which also takes out 3rd and 5th and usually sets P0776. GM bulletin 09-07-30-012F covers it. The fix is a teardown with an updated plate, a full debris clean, a new pump fluid filter and a new control solenoid filter plate.

Is the Acadia transmission covered by a GM extended warranty?

GM special coverage 14404B covered the wave plate failure on 2007-2009 Acadias for 10 years or 120,000 miles from the in-service date, whichever came first. All of those vehicles are now past ten years, so the repair is customer-pay today.

How much transmission fluid does an Acadia take?

GM's 2012 Acadia manual lists a drain-and-refill of 5.0 L (5.3 qt) of DEXRON-VI. A full overhaul takes much more; GM's wave plate coverage repair calls for nine quarts. The fluid will not reach the dipstick until the transmission is at operating temperature, so do not top it off cold.

What causes an Acadia to shudder when accelerating from a stop?

On a 2014-2019 Acadia, GM bulletin 18-NA-358 traces launch, 4th-gear and 2-3 shift shudder to debris or scoring in the upper and lower valve bodies, fixed by replacing both together. Rule out an engine misfire and torque converter clutch shudder first, and do not replace the TEHCM, which GM says has not fixed this concern.