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Discussion Starter · #1 ·
Hello all, new to the forum.

If anyone is in the North Colorado area and needs trans work for these piles, the AAMCO in Greeley, CO was excellent. Because they are excellent; they are busy! I had to book almost two (2) months out for my appointment! They even dealt with CNA National Warranty for me who ended up footing the whole bill less my $50 deductible.

For anyone else researching this, my symptoms:
1 - A bucking or rumble strip feeling when accelerating moderately. Gets worse if maintain throttle position or goes away if you change throttle position
2 - When cruising on the highway the tachometer jumps up & down +200 RPM. Usually accompanied by a rumble strip feeling
3 - An RPM flare up when the trans is shifting from 2nd to 3rd under moderate to aggressive acceleration

I drive 120 miles a day for my commute with half of it cruising @ 90MPH with the rest of traffic. My 2015 Acadia AWD had 120k miles at the time. I had thought the trans was only just beginning to wear out so I wasn't concerned that I put an additional 4k miles on it until the appointment.

I dropped it off the night before and the next morning (Nov 22) they diagnosed that the Torque Converter clutch was toast and the clutch packs for 1, 2, 3, 4, & 5 were toast. When they called they stated: "We kept the test drive as short as possible so we don't burn it up in case you aren't ready for a rebuild." They were surprised when I told my driving conditions and how long it had been persisting. [Once AAMCO had it fully torn down the only clutch pack still in decent form was the 6th speed OD clutch. Kinda funny since I spend so much time doing 90 in 6th]

Now on to dealing with CNA National Warranty. CNA demanded the whole trans be torn apart and single point of failure found for them evaluate the situation. CNA did not accept the diagnoses write up as reason to cover the transmission. They also would not authorize the teardown though as they would not pay for it unless they end up covering the work in the end. So I approved the tear down which was now Tuesday (Nov 23) before Thanksgiving. Wednesday (Nov 24) AAMCO sent me pictures and attempted to contact CNA. Unfortunately they were closed the remainder of the week. The tear down showed that every single screen for the valve body was plugged, the main fluid filter was plugged, and that the clutch packs for 1, 2, 3, 4, & 5 were on the very edge of completely burning up which would have left me stranded.

Thankfully AAMCO went ahead and ordered all new everything for the rebuild so it would be on hand once the approval came in. CNA was not interested in pictures and requested an investigator the Monday (Nov 29) after thanksgiving who did not show up until Wednesday (Dec 1). CNA did not review the report until Friday morning (Dec 3) but thankfully they approved the full rebuild and labor! Once AAMCO received approval they began working on the trans and rolled my Acadia back in from the lot. AAMCO was originally hoping to have it finished by Monday (Dec 6) or Tuesday (Dec 7) at the latest. To my surprise they called up Saturday afternoon (Dec4) stating they had stayed late and were almost done. For some reason the relearn didn't save on the test drive. So they only needed Monday (Dec 6) morning to finish. I picked up Monday night and everything looks perfectly back in place. It is definitely learning the new guts and my driving style but is back to rock solid. No more jerking/rumble strip/jumping tachometer.

The guys were very professional and easy going the whole time over the phone even when CNA was being annoying. Good news is that AAMCO said CNA was one of the best warranty companies to deal with. CNA did not try beat up the shops diagnosis, price, or pinch the parts being replaced. Once CNA read the inspector report they 100% bought into AAMCO's SOW. (Statement of Work) CNA also covered my rental for 10 days which is covered under policy.

* TIPS *
1) If you are dealing with CNA National, and a shop has diagnosed your transmission as bad, have them immediately tear down the transmission. It will save you time and frustration.

2) The manual states that for normal driving conditions the transmission fluid is lifetime. If you missed the 30K service interval DO NOT service the fluid. My transmission had so much material suspended in the fluid that it was actually helping the burn out clutch packs. AAMCO stated if I had drained the fluid the transmission would have been worse as the clutches would no longer have any extra grabbing material.

3) Only buy these Acadia's used with a reputable warranty! My uncle had a 2012 Acadia and got screwed the week before he was going to trade it in on the 2015. When he bought this 2015 he purchased the CNA warranty and transferred it to me. I knew fully well the transmission was going to die.




I will post some pics later of the worn out internals.
 

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For starters, just because you had a good experience with an aftermarket third-party warranty, doesn't mean others will have the same. Recommending that an owner authorize a teardown of the transmission without authorization on behalf of the warranty company seems negligent. Should the warranty company deny the claim for any reason, the owner is then on the hook for the cost of the transmission diagnosis, the cost of any repairs or replacement, and left without a functioning vehicle, if it was drive-able before the teardown.

Secondly, just because you haven't exchanged the ATF at the 'severe' service intervals, does not preclude you from doing it later.

Thirdly, I don't think it's a given that the later editions of the 6T75 transmission are prone to the same failures as the pre-2013 units. A number of internal changes were made to the solenoids and valve body for the 2013 refresh, amongst other things. From the sound of it, you're in Colorado and were driving 90 MPH in elevation. If you're not using the ERS, that tranny must have been shifting ALL the time at those speeds and atmospheric conditions, because I know how mine functions at 80 MPH just in Michigan.

So yes, I think you got lucky that your warranty experience turned out so well, for a vehicle that was beaten to death because of poor understanding of how to drive it at elevation.
 

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Discussion Starter · #5 ·
For starters, just because you had a good experience with an aftermarket third-party warranty, doesn't mean others will have the same. Recommending that an owner authorize a teardown of the transmission without authorization on behalf of the warranty company seems negligent. Should the warranty company deny the claim for any reason, the owner is then on the hook for the cost of the transmission diagnosis, the cost of any repairs or replacement, and left without a functioning vehicle, if it was drive-able before the teardown.

Secondly, just because you haven't exchanged the ATF at the 'severe' service intervals, does not preclude you from doing it later.

Thirdly, I don't think it's a given that the later editions of the 6T75 transmission are prone to the same failures as the pre-2013 units. A number of internal changes were made to the solenoids and valve body for the 2013 refresh, amongst other things. From the sound of it, you're in Colorado and were driving 90 MPH in elevation. If you're not using the ERS, that tranny must have been shifting ALL the time at those speeds and atmospheric conditions, because I know how mine functions at 80 MPH just in Michigan.

So yes, I think you got lucky that your warranty experience turned out so well, for a vehicle that was beaten to death because of poor understanding of how to drive it at elevation.
Well, I only just moved to CO and recently bought this from my uncle. I'm only 20K miles into the car myself. This car has spent 100k miles in Mass. driving through Boston and 80 on the highway.

CNA National is only available if the car is a Certified Used from a dealer and it is one of the reputable warranties. That's why I said buy a reputable warranty.

While on the highway the trans really is only shifting between 5th and 6th for the occasional hill. Plus we all know ERS doesn't do squat cause it'll pick whatever gear anyways. Also, transmissions are designed to shift... What do you think they are doing when driving through any given city?
 
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