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6T75 Gen 2 in older Acadia?

19K views 28 replies 4 participants last post by  lamping.ap 
#1 ·
Does anyone know or have a way to find out if a gen 2 6T75 transaxle (from 2013-2016) can go into an older Lambda, particularly a 2012? It seems that quite a few improvements were made to the design (including the TEHCM) and if I'm going to replace this thing, I'd like to grab the "refreshed" version. A low mile unit can be had at a JY for ~$800. I know it will bolt up. I know the TEHCM will need to be programmed at the dealer. What I don't know is if the gen 2 TEHCM will be compatible communication-wise with the rest of my 2012. Thoughts?

Ref: http://www.atra.com/Gears/2013/2013-12/2013_12_28.pdf
Issue: https://www.acadiaforum.net/305643-post17.html
 
#2 · (Edited)
There's a group called ATRA (Automatic Transmission Rebuilders Association) with a lot of 'net presence. Might be a good source for info if you can find a contact page. Most of the reading I've done (both ATRA and Sonnax sites) suggests hardware and software changes are such that it might not be possible to interchange the two generations of this transmission.

Wouldn't it be nice if that could be done? Let us know what you find out if no one comes up with a concrete answer here.
 
#3 ·
Ha. ATRA is the ref I linked to that shows the changes in the generations. I'll keep digging. Is KeyDiesel still around? I'd think he would have the knowledge here.
 
#4 · (Edited)
I was actually suggesting you make personal contact with them. Haven't seen KeyDiesel around in ages. Try the contact page on this website, http://www.keydiesel.com/, and see if someone from Key Diesel is the person who signed in as the forum member. The location is correct. They're also available on Facebook.
 
#5 ·
This is the response I got from ATRA: "Ususally the GEN 1 and GEN 2 are separated by parts updates and program updates. The transmission as a whole can be swaped as long as the same motor is used however the PCM might not be able to take the later design program. It might be something that the Transmisison and the PCM are replaced and reprogramed to fit."

I had a transmission shop look into it. They contacted ATSG. ATSG told them the 6T75 Gen 1 could be replaced with a Gen 2 as long as the complete assembly, including the TEHCM, is replaced. Then, of course, the dealer would need to program the whole thing.

So, I guess the next steps for me is to go to the dealer and make sure a 2012 ECM is compatible with a Gen 2 TEHCM or can be programmed to be.
 
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#7 ·
...
So, I guess the next steps for me is to go to the dealer and make sure a 2012 ECM is compatible with a Gen 2 TEHCM or can be programmed to be.
That might be a question for someone with intense coding experience, like GTPrix. A dealer probably wouldn't be interested in that type of program modification. Do you have Chris White's (GTPrix) contact info? It's available in some thread of the forum.
 
#8 ·
Too much work to do some digging? The `12 was ~$38k. Trade in is about ~$10k. 6 years means it was ~$400/month to own and that doesn't include anything (oil, brakes, etc.). At that rate owning this car is stupid and one should lease.
 
#12 ·
I like it!! Looks as though it could useful for any number of tasks if one knows how to read/write code for these computers on wheels. :wink:
 
#13 · (Edited)
I haven't heard back from that company yet about flashing, but I wanted to correct something I said in this post: https://www.acadiaforum.net/306059-post5.html

I talked to the ATSG again and they said any 6T75 can go into any Lambda as long as you use your original TEHCM. This supports what another member said here a years ago. The TEHCM (valvebody and TCM) must match your model year to be safe, but there are a couple that overlap (11-12, 13 by itself, 14-16). We all know that a TEHCM from a different car requires programming, but saying it anyway.

So, I'm probably going to grab one from a 2015, a Gen 2, with next to no miles on it and swap my TEHCM into it and be on my way. Also, according to the shops and the ATSG all of the mechanical rebuild parts for re-manufacturing are the same for both generations, even for the parts that changed (figure 1 in the previous ref link), minus the valvebody. This supports their compatibility. They basically said a completely remanufactured Gen 1 is a Gen 2, but with the original years TEHCM.
 
#14 · (Edited)
... We all know that a TEHCM from a different car requires programming, but saying it anyway. ...
The TEHCM is the major change between GEN-1 and GEN-2. They eliminated the solenoids and those switch membranes. That's why they say to stay with the original generation TEHCM. The power train control module (PCM) of a GEN-1 TEHCM equipped car doesn't have the programming to control a GEN-2 TEHCM, and vice versa. Makes me think the mod could take place easily if the PCM was a stand alone module. Unfortunately, it's part of an ECM/PCM package.
 
#15 · (Edited)
^^^^^ bingo!

But to add to that, I talked to a couple of dealers. As far as programming goes, they just input your VIN when programming. I'm not sure if this is the case or not, but it leads me, and those I talked to, to assume that the modules will simply be programmed to match the version of the software made for your VIN (model year and RPO code combination). This would lead to a Gen 2 TCM being programming incorrectly (as a Gen 1) or maybe even refusing the program. Again, this is speculative and no one that I've talked to actually knows.
 
#16 · (Edited)
Just a quick update:
- I picked up a Gen 2 6T75 from a 2015 Buick Enclave at the JY for $1000. It reportedly had 10 miles on it. Yes, only 10. It must have been a freight damaged vehicle. I have the VIN, but didn't pay to look it up. If anyone has a subscription to a VIN check, I'd be happy to share the VIN to confirm.

- After pulling the trans out, I swapped the valve assembly and TEHCM from my Gen 1 trans to the Gen 2. This was to make it compatible with my model year and avoid dealer programming.

- I suspended the engine and steering rack, but removed everything else from the bottom (exhaust flex pipe, transfer case, subframe, left cat converter, starter, trans). I disconnected the propeller shaft at the transfer case and secured it up, not removing it. I hung the calipers on the strut assembly. The CV half shafts were removed with the hub, knuckle, and rotor attached, disconnecting the knuckle from the strut. I also took out the fender liners to make it easier for the other jobs.

- I installed new GM subframe bushings, new KYB front struts, new GM subframe mounting bolts (8 bolts of the 12, the 4 smaller bolts for the rear end aren't called out to be replaced), new GM front and rear engine mounts (with new nuts purchased from McMaster Carr -- where I also bought 2 threaded rods to serve as guide pins for the transfer case install), new GM trans mount, new GM transfer case o-ring (where it meets the trans), new MOOG sway (or stabilizer, whatever you refer to it as) bar bushings, and new exhaust gaskets/seals (2 Felpro for the flex pipe to cat, 1 GM from the flex pipe to rear main cat, and 1 Felpro seal for the cat to manifold).

- I've put about ~50 miles on it so far and all seems well. I just need to get the car aligned to finish this up. Doing this without dropping the engine or complete subframe assembly was a PITA and likely greatly increased the duration of the job. It was done this way because of the type of lift I had access to (4 post). A lot of time was wasted fussing with gaining access to things and lining things up. In all, it took about 4 long days.

- Does anyone need a valve assembly and TEHCM for a 2014-2016 Lambda?

- Photos: Full album here - https://imgur.com/a/zqa7QAh
 
#17 ·
Way to go, @lamping.ap! :clap: Hope it works well for years to come. Did you also check the solenoid laminate disks in your car's TEHCM while you had it out of the transmission?
 
#18 ·
Thanks. I gave the pressure switches a look over and all looked as it should. I toyed around with the idea of replacing it anyway (before I started the job), but decided against it. In hindsight I probably should've to prevent future issues... time will tell. I probably should've replaced the filter plate on it at the very least, but over looked it when I was getting parts together. Oh well.

I drove it again today and the downshifts aren't as smooth as I'd like. I'm taking it in for the liftgate prop rod recall (way overdue) and alignment. I'm going to see if they'll reset the trans adaptives while they have it plugged in. Were there any software updates for the 2012 model year for the TCM?
 
#19 ·
I'm not aware of any transmission software updates beyond the earlier years. Maybe the new stuff has to adapt itself to your driving. ???
 
#20 ·
Yes. The TCM needs to adjust its timing for the new clutches. It definitely has gotten better since the first set of shifts. All upshifts are smooth, but a couple downs on the lower end give you a little jerk still. I'd be nice if the dealer would push the reset button to speed up the learning process.
 
#21 ·
... It would be nice if the dealer would push the reset button to speed up the learning process.
I think a dealer reset to factory defaults would slow down that process. You'd be starting from square one! The TEHCM already has some of the adaptive info from before the change. :shrug:
 
#25 · (Edited)
Quick gotcha/follow-up: Don't use Felpro exhaust gaskets for the cat-to-flex pipe connection. Use OEM.

A month or so after this work, p0420 popped up. I did the usual "Let's diagnose this." I found that there was a pretty substantial exhaust leak at that connection. I went to the dealer and got new OEM gaskets (re-did the other bank as well). The OEM gaskets are very different in terms of material and thickness. I put it back together and it's been well for over a month. Just wanted to throw this info out there.
 
#26 ·
gen 2 - 6T75 in a 2008 Acadia?

First off, you guys are awesome! It is actually inspiring, and thank you for documenting this and taking the time to post it.
Another thread (referenced early in this thread) says that with the original TEHCM (Valve body & TCM) a 2011/12 - 6T75 could be put into the 2007-09 Acadia.
Now you've gone a done the same thing with 2nd gen 6T75 (from 2015 Buick Enclave) to your 2012 Acadia.
---
I have a 2008 Acadia, so in theory and with your proven logic, should be able to put in say the same transmission you did? As long as I am using my original TEHCM. RIGHT?
 
#27 · (Edited)
I have a 2008 Acadia, so in theory and with your proven logic, should be able to put in say the same transmission you did? As long as I am using my original TEHCM. RIGHT?
Correct. Use either your original TEHCM, or a new one of the same generation as long as it's programmed for YOUR car. Programming of major command modules is not 'generic' - the programs are matched with the VIN.
 
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